A Beginner’s Guide toWater Management —The ABCsDescriptions of Commonly Used Terms

Information Circular 101

Florida LAKEWATCHDepartment of Fisheries and Aquatic Sciences

Institute of Food and Agricultural SciencesUniversity of FloridaGainesville, Florida

August 2000

UF/IFAS Communications

This publication was produced by

Florida LAKEWATCHUniversity of Florida/Institute of Food and Agricultural SciencesDepartment of Fisheries and Aquatic Sciences7922 NW 71st StreetPO Box 110600Gainesville, FL 32611-0600

Phone: (352) 392-4817Fax: (352) 392-4902Citizen message line: 1-800-LAKEWATCH (525-3928)

E-mail: lakewat@ufl.eduWeb address: http://lakewatch.ifas.ufl.edu/

Copies are available for download from the LAKEWATCH Web site:http://lakewatch.ifas.ufl.edu/LWcirc.html

or from the

UF/IFAS Electronic Document Information Source (EDIS) Web site:http://edis.ifas.ufl.edu

Copyright © 2000Limited reproduction of and/or quotation from this book is permitted, providing proper credit is given.

A Beginner’s Guide toWater Management —The ABCsDescriptions of Commonly Used Terms

Information Circular 101

Florida LAKEWATCHDepartment of Fisheries and Aquatic Sciences

Institute of Food and Agricultural SciencesUniversity of FloridaGainesville, Florida

August 2000

One of the goals of the Florida LAKEWATCH Program is to bridge theinformation gap between the scientific community that studies Florida’s waters andthe people who want to learn about the lakes, rivers and streams they care for. Thefirst step toward achieving this goal is to define a commonly understood language.

Language is a funny thing. Words can mean different things to different people— even when they are speaking the same language. From the lay public’s view-point, scientific terminology might as well be a foreign language. Unfamiliar wordsmay convey unintended meanings, or sometimes, no meaning at all. Even the mostintelligent or well-educated listeners cannot be expected to translate a specializedscientific language without a guide, especially when the language is not part of theireveryday experience.

This document is the first in a series of Information Circulars the LAKE-WATCH Program is developing for the public. It is an introduction to the basicterminology and concepts used in the water management arena. Not all scientistsand water managers may use the included terminology in precisely the same way.The descriptions used here represent water management as Florida LAKEWATCHprofessionals have come to understand it.

Prologue

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When faced with the task of explaining howthings work in the physical world, scientists

developed an investigativeprocess called the scientificmethod. This system hasbeen used for centuries andcontinues to be used today.

Ideally, the scientificmethod proceeds in stages.First, observations are made.These are considered to befacts. Then suppositions,called hypotheses, are madethat seem to explain the cause-and-effect relationship amongthe facts. A hypothesis is ahighly tentative statement — ahunch about how things work.Next, experiments are performedto test whether a hypothesiscan correctly account for theexperimental results that areobserved.

During this stage, measurements called “data”are taken. If the data are consistent with the predic-tions made using the hypothesis, the hypothesisgains credibility. If not, the hypothesis is eitherdiscarded or modified. A hypothesis often goesthrough many revisions. After repeated experimentalverifications, a hypothesis becomes a theory. Thedistinction between a hypothesis and a theory hasbecome blurred in recent years.

A theory is not a tentative statement like ahypothesis — a theory has a high probability ofbeing correct. For a theory to become accepted bythe scientific community, there must be a consensusin the scientific community that a theory representsthe truth.

The lay person should bear in mind that eventhough a scientific theory is believed to be credibleby the scientific community, it could still be wrong.

Widely accepted theories are difficult tochallenge, so they often persist. Scientists have

been known to developparental, protective attitudestoward their theories, some-times defending them with azeal that is far from objective.1

Challengers face skepticism,even derision, which hasoften brought tragic personalconsequences. History isreplete with examples.

On the other hand,Nobel Prizes have beenawarded to scientists whohave had the courage andvision to contest populartheories in favor of new, moreaccurate ones.

Using the scientificmethod can require many yearsof gathering and evaluatingevidence, formulating and

reformulating hypotheses, and debating the value ofcompeting theories. And even after all that, anaccepted theory may eventually be proven false.

Unfortunately, developing reliable theories inthe water management arena may take years, evencenturies. In the meantime, understanding thespeculative nature of the scientific method isimportant for both the lay public and professionals.Before anyone accepts a theory or a hypothesis, heor she should always find out what evidencesupports it and whether there is any evidence thatcontradicts it.

In this way, hypotheses and widely-acceptedtheories can be put into proper perspective. Anyhypothesis or theory is only as valid as theevaluative thought process that has produced it.

Scientific Method

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1 Refer to Chamberlin’s article “The Method of MultipleWorking Hypotheses” (see references at the end of this circular).

—utilize the metric system, it will be used in thisdocument. If you want to put a measurement intomore familiar terms, you can calculate its Englishequivalent. Though converting is not necessary, it ishelpful when trying to visualize quantities.

The following table shows common metricunits and the conversion factors that can be used tocalculate their equivalents in the correspondingEnglish units. To convert a metric unit to an Englishunit, multiply the metric measurement by the con-version factor shown in the table. For example,multiply 5 meters times the conversion factor of3.281 to get 16.405 feet — 5 meters and 16.405 feetare the same distance.

To apply the scientific method properly,experiments must be performed during whichmeasurements must be made. Every measurementconsists of two parts: a number (how many?) and aunit of measure (i.e., pound, foot, second, etc.). Forexample, in the measurement 5.2 hours, the “5.2”tells how many, and “hours” is the unit of measure.

There are two primary systems used formaking measurements: the metric system and theEnglish system.

The United States is attempting to convert tothe metric system, but acceptance by the generalpublic has been slow. Because most scientificstudies—including Florida LAKEWATCH research

Metric to English Conversion Factors

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centimeter (cm) 0.3937 inch (in)

meter (m) 3.281 feet (ft)

kilometer (km) 0.6214 mile (mi)

square kilometer (km2) 0.3861 square mile (mi2)

hectare (ha) 2.471 acre (ac)

kilogram (kg) 2.205 pound (lb)

Liter (L or l) 1.057 U.S. quart (qt)

cubic meter (m3) 264 U.S. gallon (gal)

milligrams/Liter (mg/L) 1.0 parts/million (ppm)

micrograms/Liter (µg/L) 1.0 parts/billion (ppb)

Celsius (C) (C x 9/5) +32 Fahrenheit (F)

Metric Unit Conversion Factor English Unit

Multiply bythis number:

To get the equivalentin the units below:

When you have anamount in these units:

microgram per Liter (µg/L) 1 milligram per cubic meter (mg/m3)

milligrams (mg) 1000 micrograms (µg)

grams (g) 1000 milligrams (mg)

kilograms (kg) 1000 grams (g)

cubic meters (m3) 1000 liters (L or l)

Converting from one unit of measure to anotherwithin the metric system is much easier than converting

within the English system. The table below showsthe most common conversion factors.

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Metric Units

Note that the value of each metric conversion factor is indicated by theprefixes used:

milli means “one-thousandth,”micro means “one-millionth,” and

kilo means “one thousand.”

Algaeare a wide variety of tiny,often microscopic, plants(or plant-like organisms)that live both in water andon land. The word algae isplural (pronounced AL-jee),and alga is the singularform (pronounced AL-gah).

One common way toclassify water-dwelling algae is based on wherethey live. Using this system, three types of algaeare commonly defined as follows:

♦ phytoplankton (also known as planktonicalgae) float freely in the water;

♦ periphyton are attached to aquatic vegetationor other structures; and

♦ benthic algae grow on the bottom or bottomsediments.

Description of Terms Commonly Used in Water Management

Algae may further be described as beingcolonial which means they grow together incolonies, or as being filamentous which meansthey form hair-like strands. The most commonforms of algae are also described by their colors:green, blue-green, red, and yellow. All theseclassifications may be used together. Forexample, to describe blue-green, hair-like algaethat are attached to an underwater rock, youcould refer to them as “blue-green filamentousperiphyton.”

In addition to describing types of algae, it isuseful to measure quantity. The amount of algaein a waterbody is often called algal biomass.Scientists commonly make estimates of algalbiomass based on two types of measurements:

♦ Because almost all algae contain chlorophyll(the green pigment found in plants), the concen-tration of chlorophyll in a water sample can beused to indicate the amount of algae present.This method, however, does not include all typesof algae, only the phytoplankton. Chlorophyllconcentrations are measured in units of microgramsper Liter (abbreviated µg/L) or in milligrams percubic meter (abbreviated mg/m3).

Suggestions: The descriptions in this document will make more sense to youif you start by:

1) becoming familiar with the Measurement Units described on pages iii and iv so thatmetric units are not distracting to you when you encounter them in the text; and

2) reading the entries for Algae, Aquatic Macrophytes, Biological Productivity, andTrophic State. These particular entries will provide a background in the basic, often-used vocabulary and concepts.

Note: the ☛ symbol will be used to refer you to other relevantentries in this circular.

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☛ See Benthic, Periphyton, and Phytoplankton.

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☛ See Fish kill.

♦ In certain cases scientists prefer to count theindividual algal cells or colonies in a sample anduse their count to calculate the volume of the algae.

Some people consider algae to be unsightly,particularly when it is abundant. For instance, aphytoplankton bloom can make water appear sogreen that it’s described as “pea soup.”

In Florida, when chlorophyll concentrationsreach a level over 40 µg/L, some scientists willcall it an “algae bloom” or “algal bloom.” Thepublic, however, usually has a less scientificapproach. They often define an algal bloom aswhenever more algae can be seen in the waterthan they are accustomed to seeing (even thoughthis may be a low concentration in some cases).

Algal bloomsmay be causedby humanactivities, ormay be naturallyoccurring. Sometimes, what seems to be an algalbloom is merely the result of wind blowing thealgae into a cove or onto a downwind shore,concentrating it in a relatively small area, called awindrow.

The Role of Algae in Waterbodies:Algae are essential to aquatic systems. As a vital

part of the food web, algae provide the food necessaryto support all aquatic animal life. Certain types ofalgae also provide habitat for aquatic organisms.On occasion, however, they can become trouble-some and several examples are described as follows:

♦ An algal bloom can block sunlight, preventingthe light from reaching the submersed aquaticplants below.

♦ Periphyton (filamentous algae) blooms andbenthic algal blooms have the potential to interferewith other recreational uses like boating and fishing.

♦ An algal bloom can trigger a fish kill. In Florida,this is most likely to occur after several days of hotweather with overcast skies.

Health Concerns:Newspapers and magazines often present

articles describing toxic algae. However, mostalgae are not toxic and pose little danger tohumans. It should be remembered that toxicalgae can be found in all aquatic environments.

Known health problems associated withalgae have generally been associated with highconcentrations of three species of blue-greenalgae:

♦ Anabaena flos-aquae,♦ Microcystis aeruginosa, and♦ Aphanizomenon flos-aquae.

With few exceptions, only fish and inverte-brates have died from the effects of these toxicalgae.

In Florida, it’s extremely rare for algae tocause human illness or death. People are morelikely to suffer minor symptoms such as itching.Several species of algae produce gases that haveannoying or offensive odors, often a mustysmell. These odiferous gases may cause healthproblems for some individuals who have breath-ing difficulties.

To be prudent, people should inform theirdoctor if they live near or use a waterbodyoften. This has become more important recentlyas the alga Pfiesteria has been known to causesevere health problems. (Pfiesteria tends to befound primarily in tidal waters.)

And while prudence is the watchword whenusing any waterbody, it must be recognized thatpeople face greater health risks driving homefrom the grocery store than from Pfiesteria orany other toxic algae.

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☛ See Chlorophyll.

Mycrocystis euglenoid

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Algal biomassis the amount of algae in a waterbody at a giventime. In this document, all estimates of theamount of algal biomass in a waterbody will bebased on chlorophyll measurements.

In the eye of the beholder... An aquatic weed problem is often defineddifferently by people who use a waterbody indifferent ways. For instance, for an angler aweed problem may be where aquatic macro-phytes block boat access and snag fishinglines. However, for an industry manager, itmay be where aquatic macrophytes clogcooling-water intakes or interfere withcommercial navigation.

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☛ See Algae.

☛ See Algae.

☛ See Total alkalinity.

☛ See Emergent plants, Floating-leaved plants, and Submersed plants.

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Algae bloom(or algal bloom)In Florida, when chlo-rophyll concentrationsreach a level over 40 µg/L,

some scientists will callit an “algae bloom” or“algal bloom.”

Alkalinityrefers to water’s ability, or inability, to neutralizeacids. The terms alkalinity and total alkalinity areoften used to define the same thing.

Aquatic macrophytesare aquatic plants that are large enough to beapparent to the naked eye; in other words, they arelarger than most algae. The general term “aquaticplants” usually refers to aquatic macrophytes, butsome scientists use it to mean both aquatic macro-phytes and algae. (Note: Large algae such asCladophora, Lyngbya, and Chara are alsoincluded in the category of aquatic macrophytes.)

Aquatic macrophytes characteristicallygrow in water or in wet areas and are quite adiverse group. For example, some are rooted inthe bottom sediments, while others float on thewater’s surface and are not rooted to the bottom.Aquatic macrophytes may be native to an area, or theymay have been imported (referred to as exotic).

Most aquatic macrophytes are vascularplants, meaning they contain a system of fluid-conducting tubes, much like human blood

vessels. Cattails, waterlilies, and hydrilla areexamples.

Even though they are quite diverse, aquaticmacrophytes have been grouped into three generalcategories:

♦ emergent aquatic plants are rooted in thebottom sediments and protrude up above thewater’s surface;

♦ submersed aquatic plants primarily growcompletely below the water’s surface;

♦ floating-leaved aquatic plants can be rooted tothe waterbody’s bottom sediments and also haveleaves that float on the water’s surface. Examplesare waterlilies, spatterdock and watershield;

♦ free-floating plants are a diverse group thatfloat on or just under the water surface; they arenot rooted to the bottom. Examples include tinyduckweeds and water fern as well as largerplants such as water hyacinth.

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Aquatic macrophytes are a natural part ofwaterbodies, although in some circumstances theycan be troublesome. The same plant may be a“desirable aquatic plant” in one location and a“nuisance weed” in another. When exotic aquaticplants have no natural enemies in their adoptedarea, they can grow unchecked and may becomeoverly abundant.

In Florida for example, millions of dollarsare spent each year to control two particularlyaggressive and fast-growing aquatic macro-phytes — water hyacinth, an exotic aquatic plantthat is thought to be from Central and SouthAmerica, and hydrilla, an exotic aquatic plantthat is thought to be from Africa. The term“weed” is not reserved for exotic aquatic plants.In some circumstances, our native aquatic plantscan also cause serious problems.

When assessing the abundance of aquaticplants in a waterbody, scientists may choose tomeasure or calculate one or more of the following:

♦ PVI (Percent Volume Infested or Percent VolumeInhabited) is a measure of the percentage of awaterbody’s volume that contains aquatic plants;

♦ PAC (Percent Area Covered) is a measure of thepercentage of a waterbody’s bottom area that hasaquatic plants growing on or over it;

♦ frequency of occurrence is an estimate of theabundance of specific aquatic plants; and

♦ average plant biomass is the average weight ofseveral samples of fresh, live aquatic plants grow-ing in one square meter of a lake’s area.

The Role of Aquatic Macrophytes inWaterbodies:

Aquatic macrophytes perform severalfunctions in waterbodies, which are often quitecomplex. A few are briefly described below.

♦ Aquatic macrophytes provide habitat for fish,wildlife, and other aquatic animals.

♦ Aquatic macrophytes provide habitat and foodfor organisms that fish and wildlife feed on. ☛ See Algae, Fish kill, and Water clarity.

An unexpectedresult....

During theirlifetime, aquaticplants slough offdead leaves andother plant partsthat sink to thebottom. In thisway, they contributecontinually to the formation of sediments.A study of water hyacinths has shown thatamount of sediment they contributed whena herbicide was used to kill them all at oncewas less than it would have been if theplants had been allowed to live outtheir full lifetimes.

Water hyacinth (Eichhornia crassipes)

♦ Aquatic macrophytes along a shoreline can protectthe land from erosion caused by waves and wind.

♦ Aquatic macrophytes can stabilize bottomsediments by reducing the effects of wave action.

♦ The mixing of air into the water that takes placeat the water’s surface can be obstructed by thepresence of floating plants and floating-leavedplants. In this way, they can cause lower oxygenlevels in the water.

♦ Free-floating plants and floating-leaved plantscreate shade that can cause the growth of submersedplants beneath them to be slowed or stopped.

♦ When submersed aquatic plants become moreabundant, these plants can cause water to becomeclearer. Conversely, the removal or decline of largeamounts of submersed aquatic plants can causewater to become less clear.

♦ When aquatic macrophytes die, the underwaterdecay process uses oxygen from the water. Ifmassive amounts of plants die, it can result insevere oxygen depletion in the water, which can inturn cause fish and invertebrates to die from lowoxygen.

♦ Decayed plant debris (dead leaves, etc.) contrib-utes to the buildup of sediments on the bottom.

☛ See Average plant biomass, Frequencyof occurrence, PAC, and PVI.

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Aquatic plant

Average plant biomass(as measured by Florida LAKEWATCH) is theaverage weight of several samples of fresh, liveaquatic plants growing in one square meter of alake’s area. This measurement is taken separatelyfor each category of plants: submersed, floating-leaved, and emersed. Measurements of averageplant biomass are commonly used to help assess awaterbody’s overall biological productivity and toassess the abundance of the different categories ofaquatic plants present in a waterbody.

When LAKEWATCH staff measure aquaticplant biomass, they use the following procedure:

♦ Between 10 and 30 evenly-spaced samplinglocations are chosen around the waterbody;

♦ At each sampling location, sampling is performedin three zones — the emergent plant zone, thesubmersed plant zone, and the floating-leaved plantzone;

♦ At each site, a square frame (one-quarter of asquare meter in area) is tossed into the water and allabove-ground aquatic plant material that falls insidethe frame is harvested;

♦ Harvested plants are whirled around in a net bagto spin off excess water. The plants are thenweighed on a scale that measures kilograms or grams;

♦ To calculate the biomass that would be in onesquare meter, the weight is multiplied times 4; and

♦ Values from all the sites for each category ofaquatic plants are averaged separately.

The recorded weights are referred to as wetweights, because the plants are not allowed todry out internally (like dried flowers). Plantbiomass is also referred to as fresh plantweight and is reported by Florida LAKEWATCHin units of kilograms wet weight per squaremeter (abbreviated kg wet wt/m2).

floating-leaved zone

emergent plant zone

submersed plant zone ➞

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Emergentplants are

collected tocalculate

“average plantbiomass.”

Submersed plants(above) and floating-leaved plants (left)are collected. Oncecollected they arespun to shake offexcess water beforebeing weighed.

☛ See Aquatic macrophytes and Algae.

☛ See Biological productivity.A

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Some professionals weigh plants that havebeen allowed to dry internally. Others include theweight of plant roots in their biomass measurement.LAKEWATCH only uses the wet weight of above-ground plant biomass because no expensive equip-ment is required and the results are just as useful forLAKEWATCH purposes.

Benthicis an adjective describing objects/organisms relatedto or occurring in or on bottom sediments of a waterbody.

Benthic algaeare algae that grow on the bottom sediments of awaterbody. Benthic algae are most commonlyfilamentous or colonial forms, but also may bemicroscopic single-celled organisms.

Benthic algae perform various beneficialfunctions in waterbodies, but may also be trouble-some. Several examples of problems associatedwith benthic algae are described below:

♦ Benthic algal growth can snag anglers’ fishing gear.

♦ Dense benthic growth can break free of thebottom and float to the surface.

♦ Large rafts of free-floating algae may formobstructive mats that can accumulate along shorelines.

♦ Offensive odors can be produced when benthicalgae mats decompose.

The Role of Benthic Algae in Waterbodies:Benthic algae provide food and habitat for

many aquatic organisms. In this way they con-tribute to the biological productivity of aquaticsystems.

Health Concerns:Benthic algae generally do not pose a

known direct threat to human health.

☛ See Algae.

☛ See Biological productivity.

☛ See Aquatic plants, Chlorophyll, Nutrients, Trophic state, and Water clarity.

☛ See Algae and Average plant biomass.

Biological productivityis defined conceptually as the ability of a waterbody tosupport life (such as plants, fish, and wildlife).Biological productivity is defined scientifically asthe rate at which organic matter is produced.Measuring this rate directly for an entire waterbodyis difficult and prohibitively expensive by moststandards.

For this reason, many scientists base estimatesof biological productivity on one or more quantitiesthat are more readily measured. These includemeasurements of concentrations of nutrients inwater, concentrations of chlorophyll in the water,aquatic plant abundance, and/or water clarity. Thelevel of biological productivity in a waterbody isused to determine its trophic state classification.

Biomassis the amount of living matter (as in a unit areaor volume of habitat).

Calciumis a mineral that dissolves easily in water. Calciumis represented in the Periodic Table of Elements asCa. It is one of the most abundant substances inboth surface waters and ground waters.

Freshwaters around the world have higherconcentrations of calcium when they are locatedcloser to calcium-rich soils and rocks. Typical calciumconcentrations worldwide are less than 15 mg/L, butwaters close to calcium-rich carbonate rocks oftenhave calcium concentrations exceeding 30 mg/L.

Calcium enters aquatic environments primarilythrough the weathering of rocks such as limestone,which is largely composed of calcium compounds.In some circumstances, calcium can also be depos-ited in waterbodies as a result of human activities,often because of the extensive use of calcium-containing chemicals in agriculture and industry.

Bathymetric mapa depth contour map depictingthe surface area of a lake andwater depths at regular intervals.

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Having calcium in your water supply maycause inconveniences. For example, you may haveexperienced difficulties in getting soap to lather inwhat is called “hard” water. In hard water, calciumwill combine with soap molecules and inhibit theirfoaming ability. High concentrations of calcium canalso cause a crusty accumulation called “scale” to formin pipes and hot water heaters. To prevent problemswith hard water and scale formation, many citiessoften water by removing calcium from their drinkingwater supply.

The Role of Calcium in Waterbodies:Calcium has been shown to influence the

growth of freshwater plants and animals. It is anecessary structural component of plant tissues,animal bones, and animal shells. Calcium isinvolved in many chemical cycles that occur inwaterbodies, often in rather complex ways. Forexample, adding calcium carbonate to a waterbodycan either stimulate aquatic plant growth or inhibit it.

Example 1 — when calcium carbonate, in theform of lime, is added to an acidic waterbody:

♦ the lime will cause the water to become lessacidic (the pH will become higher);

♦ as the water becomes less acidic, phosphorus, anecessary nutrient, will be converted to forms thatcan then be used by aquatic plants, potentiallystimulating their growth.

Example 2 — when a waterbody is not acidic(with a pH above 8.2) and contains an abundanceof calcium carbonate :

♦ calcium carbonate will combine with the phosphorusin the water to form a solid called a “precipitate” thatcan sink to the bottom or be attached to aquatic plants;

♦ plants and algae will be deprived of phosphorusand their growth can be slowed.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadaverage calcium concentrations ranging from 0.2 to94 mg/L. Over 75% of these waterbodies hadcalcium concentrations less than 16 mg/L.

Health Concerns:Calcium in waterbodies is not known to have

any severe effects on human health. Drinking largeamounts of hard water when the body is accustomedto soft water, however, may have a laxative effect.

Chlorideis a substance found in all the world’s waters. Chlorideis an ionized form of the element chlorine. It isrepresented in the Periodic Table ofElements as Cl. The symbol for thechloride ion is Cl –.

Chloride compounds are usedextensively in industrial operationsand agriculture. For example, thepotash in fertilizer is potassiumchloride. Common table salt issodium chloride and is a necessarypart of human and animal diets.

Chloride levels in waterbodiesare affected by several factors.Climate is a major influence. Forexample, chloride concentrations inwaterbodies in humid regions tend to below, whereas those in semi-arid and aridregions may be hundreds of times higherbecause of higher rates of evaporation.Seawater often has a reported chlorideconcentration exceeding 15,000 mg/L, butthe chloride levels vary considerably worldwide.

The activities of people and animals can alsoaffect chloride concentrations. For example, becausechloride is found in all animal and human wastes,septic systems and areas where animal wastes aredeposited may be sources of chlorides in waterbod-ies. Home water softening systems and fertilizersalso are sources of chlorides. For these reasons, thepresence of chlorides can sometimes be used as anindicator of pollution from these sources.

The Role of Chloridesin Waterbodies:

Salts are the primary sources of chloride inwater. (The term “salt” includes compounds inaddition to sodium chloride.) Traveling by manypathways, chloride has found its way into all theworld’s waters. Many coastal waters have highconcentrations of chloride, because they are close tomarine (i.e., saltwater) systems. In these waterbodies,

☛ See Limiting environmental factors,pH and Total phosphorus.

seawater can seep underground, called saltwaterintrusion, or flow directly into them through tidalflow, for instance. Also, sea spray carries chlorideinto the air where it can then enter waterbodies aspart of rainfall, even far from coastal areas.

The saltiness, or chloride concentration, ofwater can affect plants and wildlife. For example,some species die in water that is too salty, andothers die in water that is not salty enough.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadaverage chloride concentrations ranging from 1.7 to2300 mg/L. Over 75% of these waterbodies hadchloride concentrations less than 22 mg/L.

Health Concerns:Chloride concentrations in lakes are generally

so low that they pose no known threat to humanhealth. Water will have a strong salty taste ifchloride concentrations exceed 250 mg/L.

It should be noted that although the chlorides arenot dangerous themselves, they signal the possibilityof contamination from human or animal wastes thatcan contain bacteria and other harmful substances. Forthis reason, it is prudent to investigate where thechlorides are coming from when high concentrationsare detected in an inlandwaterbody.

Chlorophyllis the green pigmentfound in plants andfound abundantly innearly all algae. Chloro-phyll allows plants andalgae to use sunlight inthe process of photosynthesis for growth. Thanks tochlorophyll, plants are able to provide food andoxygen for the majority of animal life on earth.

Scientists may refer to chlorophyll a, whichis one type of chlorophyll, as are chlorophyll b andchlorophyll c. Measurements of total chlorophyllinclude all types. Chlorophyll can be abbreviatedCHL, and total chlorophyll can be abbreviatedTCHL.

The Role of Chlorophyll in Waterbodies:Measurements of chlorophyll concentrations

in water samples are very useful to scientists. Forexample, they are often used to estimate algalbiomass in a waterbody and to assess a waterbody’sbiological productivity.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadaverage chlorophyll concentrations ranging fromless than 1 to over 400 µg/L. Using averagechlorophyll concentrations from this samedatabase, Florida lakes were found to be distributedinto the four trophic states as follows:2

♦12% of the lakes (those with chlorophyll valuesless than 3 µg/L) would be classified as oligotrophic;

♦ about 31% of the lakes (those with chlorophyllvalues between 4 and 7 µg/L) would be classifiedas mesotrophic;

♦ 41% of the lakes (those with chlorophyll valuesbetween 8 and 40 µg/L) would be classified aseutrophic; and

♦ nearly 16% of the lakes (those with chlorophyllvalues greater than 40 µg/L) would be classified ashypereutrophic.

In Florida, characteristics of a lake’sgeographic region can provide insight into howmuch chlorophyll may be expected for lakes inthat area. For example, water entering the water-bodies by stream flow or underground flowagethrough fertile soils can pick up nutrients thatcan then fertilize the growth of algae and aquaticplants. In this way, the geology and physiographyof a watershed can significantly influence awaterbody’s biological productivity.

☛ See Lake region.

☛ See Algae, Algal biomass, Biologicalproductivity, and Phytoplankton.

☛ See Trophic state and each of its categories:Oligotrophic, Mesotrophic, Eutrophic, andHypereutrophic.

LAKEWATCH volunteers filter lakewater monthly to collect chlorophyllsamples.

2 This distribution of trophic state is based solely on chlorophyll valueswithout utilizing information on nutrient concentrations or water clarity.

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Health Concerns:Chlorophyll poses no known direct threat to

human health. There are some rare cases wherealgae can become high enough in abundance tocause concern. However, toxic algae are generallynot a problem.

☛ See Algae.

Colorin waterbodies has twocomponents:(1) apparent color isthe color of a watersample that has not hadparticulates filtered out;(2) true color is the colorof a water sample thathas had all particulatesfiltered out of the water.

The measurementof true color is the one most commonly used byscientists. To measure true color, the color of thefiltered water sample is matched to one from aspectrum of standard colors. Each of the standardcolors has been assigned a number on a scale ofplatinum-cobalt units (abbreviated as either PCUor Pt-Co units). On the PCU scale, a higher value oftrue color represents water that is darker in color.

The Role of Color in Waterbodies:Dissolved organic materials (humic acids from

decaying leaves), and dissolved minerals can givewater a reddish brown “tea” color.

The presence of color can reduce both thequantity and quality of light penetrating into thewater column. As a result, high color concentra-tions (greater than 50 PCU) may limit both thequantity and types of algae growing in a waterbody.Changing the quantity and quality of lightreaching the bottom of a waterbody can alsoinfluence the depth of colonization and the typesof aquatic plants that can grow there. In somewaterbodies, color is the limiting environmentalfactor.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadaverage color values ranging from 0 to over 700PCU. Over 75% of these waterbodies had colorvalues less than 70 PCU.

Waterbodies that adjoin poorly drained areas(such as swamps) often have darker water, especiallyafter a rainfall. Consequently, the location of awaterbody has a strong influence on its color.For example, lakes in the well-drained New HopeRidge/Greenhead Slope lake region in northwest-ern Florida (in Washington, Bay, Calhoun, andJackson Counties) tend to have color values below10 PCU. While lakes in the poorly-drainedOkefenokee Plains lake region in north Florida (inBaker, Columbia, and Hamilton Counties) tend tohave values above 100 PCU.

Health Concerns:There is no known direct health hazard of

color. Consequently, an acceptable level of colordepends on personal preference. Water transpar-ency, however, may be reduced in highly coloredwaters (greater than 50 PCU) to the point whereunderwater hazards may be concealed, creating apotentially dangerous situation for swimmers,skiers, and boaters.

☛ See Humic acids, Limiting environmentalfactor, and Water clarity.

☛ See Lake region.

☛ See Plant species and Scientificplant name.

Commonplant namePlants have scientific namesand common names. Forexample, the floating aquaticplant known scientifically asNuphar luteum is alsoknown by several common names—bonnet, cowlily or spatterdock. It’s important to note that thecommon name may vary depending on whichregion of the state you might be in. Also, the samecommon name is sometimes even used for differentplants. Scientists usually choose to identify plantsby their scientific name, to eliminate this confusion.

Spatterdock (Nuphar luteum)

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☛ See Average plant biomassand Biological productivity.

☛ See Specific conductance.

Emergentplantsare aquatic plantsrooted in bottomsediments withleaves protrudingabove the water’ssurface. Cattail,maidencane, and bulrush are examples of emergentplants. Emergent plants grow in water-saturatedsoils and submersed soils near the edge of awaterbody. They generally grow out to a maxi-mum depth of from 1 to 3 meters (about 3 to 10feet). Emergent plants perform many functionsin waterbodies:

♦ Emergent plants provide habitat for fish.

♦ Emergent plants provide food and habitat forwildlife populations such as ducks.

♦ Emergent plants reduce shoreline erosion.

♦ Emergent plants increase evapotranspirational3

water losses from a waterbody, sometimes to thepoint where water levels are lowered.

♦ Emergent plants shed leaves and other plantdebris, adding to the bottom sediments and makingthe water shallower.

♦ As emergent plant debris accumulates in shallowwater areas, shorelines migrate lakeward.

♦ Uprooted plants can form floating islands calledtussocks that can be significant navigationalhazards and block access to parts of the waterbody.It should be noted tussocks also provide bird andwildlife habitat.

Emergent plants react in various ways tochanging water levels. When periods of low waterare followed by a rapid rise in water level, largesections of emergent plants may be uprooted.Sustained high water can also reduce emergent

plant abundance. In periods of low water, debrisfrom emergent plants is a significant factor.Accumulated plant debris can eventually (i.e.,100-10,000 years) cause the lake to becomemore shallow, eventually forming a swamp ormarsh, and ultimately, peat deposits.

In Florida:Emergent plants occur naturally in all

Florida waterbodies. The width of the emergentzone (from the shoreline out into the lake) mayvary from a few meters to hundreds of meters.Its size changes most often in response to chang-ing water levels. If emergent plants have beenallowed to grow without human intervention,the lakeward edge of the emergent plants can beused to show where a waterbody’s low waterlevel has been in the past few years or perhapseven decades.

Health Concerns:Emergent plants are not generally thought

of as a cause of human health problems. How-ever, dense growths of emergent plants providehabitat that can harbor disease-carrying mosquitoes.

Conductance (or Conductivity)

Emergent plant biomass(as used by Florida LAKEWATCH) is theaverage weight of fresh, live emergent aquaticplants growing in one square meter of a lake’sbottom area. The measurement of averageemergent plant biomass in a waterbody is one ofseveral measurements that can be used to assessa waterbody’s overall biological productivity.

In Florida:Average emergent plant biomass in Florida

lakes generally ranges from 0 to 27 kg wet wt/m2. Emergent plant biomass appears to be linkedwith a waterbody’s biological productivity. Forexample:

Annual Spikerush (Eleocharis geniculata)

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3 Evapotranspiration is different from evaporation. Evapotranspirationis the process in which water evaporates from the surface of plants or isemitted as a vapor from the surface of leaves or other plant parts.

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☛ See Aquatic macrophytes, Emergentplant biomass and Width of emergentand floating-leaved zone.

♦ in biologically less productive lakes (oligotrophiclakes), the average emergent plant biomass is about2.5 kg wet wt/m2;

♦ in moderately productive lakes (mesotrophiclakes), the average emergent plant biomass is about3.0 kg wet wt/m2;

♦ in highly productive lakes (eutrophic lakes), theaverage emergent plant biomass is about 3.5 kg wetwt/m2; and

♦ in the most highly productive lakes (hypereutrophiclakes), the average emergent plant biomass is about4.0 kg wet wt/m2.

☛ See Trophic state and each of its categories:Oligotrophic, Mesotrophic, Eutrophic, andHypereutrophic.

☛ See Algae, Aquatic macrophytes,Chlorophyll, Fish kill, Hypereutrophic,Mesotrophic, Oligotrophic, Secchi depth,Trophic state, and Water clarity.

Eutrophicis an adjective used to describe the level of biologi-cal productivity of a waterbody. Florida LAKE-WATCH and many professionals classify levels ofbiological productivity using four trophic statecategories: oligotrophic, mesotrophic, eutrophic,and hypereutrophic. Of the four trophic statecategories, the eutrophic state is defined as having ahigh level of biological productivity, second onlyto the hypereutrophic category. (The prefix “eu”means good or sufficient.)

A eutrophic waterbody is capable of producingand supporting an abundance of living organisms(plants, fish, and wildlife). Eutrophic waterbodiesgenerally have the characteristics described below:

♦ Eutrophic lakes are more biologically productivethan oligotrophic and mesotrophic lakes. Some of

Florida’s best fishing lakes are often eutrophic,supporting large populations of fish, includingsportfish such as largemouth bass, speckled perch,and bream.

♦ Typically, eutrophic waters are characterized ashaving sufficient nutrient concentrations to supportthe abundant growth of algae and/or aquatic plants.

♦ When algae dominate a eutrophic waterbody,chlorophyll concentrations will be high — greaterthan 7 µg/L. The result will be less clear water;Secchi depth readings will be low (less than 8 feet).

In contrast, when aquatic plants dominate aeutrophic waterbody (instead of algae), chloro-phyll concentrations and nutrient concentrationswill be lower and the water will be clearer.Secchi depth readings will be greater (largernumbers) than they would be in eutrophic water-bodies with fewer plants.

Despite being classified as eutrophic, theseplant-dominated waterbodies display the clearwater, low chlorophyll concentrations, and lownutrient concentrations that are more characteristicof mesotrophic or oligotrophic waterbodies.

♦ Regardless of whether eutrophic waterbodiesare plant-dominated or algae-dominated, theygenerally have a layer of sediment on the bottomresulting from the long-term accumulation ofplant debris. In some eutrophic lakes, however,the action of wind and waves can create beachesor sandy-bottom areas in localized areas.

♦ Eutrophic waterbodies can have occasionalalgal blooms and fish kills. However, fish killsgenerally occur in hypereutrophic lakes whenchlorophyll concentrations exceed 100 µg/L.

Fish killis an event in which dead fish are observed. Some fishkills are extremely noticeable and may be viewed bythe public as being damaging to the fish population.However, contrary to their appearance, typical fishkills in lakes only affect a small percentage of the fish

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in a waterbody. Fish kills may occur for several reasons.The most common cause of fish kills is related

to the depletion of oxygen in shallow waterbodies.Oxygen depletion may be caused in various ways.Three of the most common are as follows:

1 Whenever aquatic organisms die, oxygen is pulledfrom the water column and is used in the decayprocess. Oxygen can become critically reduced in thisway, especially in waterbodies that have an abundanceof algae. For waterbodies in which the concentration oftotal chlorophyll exceeds 100 µg/L (indicating a highalgae level), oxygen depletion is a likely cause of a fishkill. This is because the fraction of the algal populationthat is dying naturally is a large amount of mass; andtherefore, its decomposition can consume significantamounts of oxygen.

2 Similarly, oxygen depletion can also occurwhen large amounts of aquatic plants die within ashort time. Herbicide applicators commonly treatareas of aquatic plants at different times in order toavoid this situation, or they use herbicides thatcause plants to die slowly.

3 A fish kill due to oxygen depletion can also betriggered by several days of overcast skies, espe-cially during hot weather. This can happen becauseaquatic plants and algae add oxygen to water onlywhen there is sufficient sunlight for photosynthesis;however, they consume oxygen all the time in theirnormal biological processes. When overcast skiespersist for several days, oxygen levels can becomedepleted because the plants are using more oxygenthan they are producing. Waters are particularlyvulnerable when the temperature is high, becausewarmer water contains less oxygen to start with thancooler water. Fish “gulping” at the surface may be asign of an oxygen problem.

Some species of fish die naturally in largenumbers after spawning or when they are stressed byunusual or harsh weather conditions. High concen-trations of hydrogen sulfide (perhaps from a sulfur-water spring or artesian well) may be the cause of afish kill. In this case, sometimes a rotten egg smell isnoticeable.

Floating-leavedplantsare aquatic plants that areprimarily rooted to bottomsediments and also haveleaves that float on the water’s surface.(Note: Although usually not rooted on the bottom,free-floating plants such as water hyacinth andwater lettuce are sometimes included in thisplant classification.)

Waterlilies, spatterdock, and lotus areexamples of floating-leaved plants. Floating-leaved plants are generally found growing alongthe shoreline, lakeward of the emergent plants.Floating-leaved plants perform many functionsin waterbodies. Some of the most common aredescribed below:

♦ According to many aquatic scientists, theprimary role of floating-leaved plants in waterbod-ies is to provide food and habitat for wildlife andfish. Food for fish is provided principally whenmany varieties of small animals feed on the algaethat have attached themselves to these plants.

♦ Floating-leaved plants can reduce shoreline erosion.

♦ Decaying material produced by floating-leavedplants accumulates in the sediments over manyyears (i.e., 100-10,000 years), playing an influentialrole in making a waterbody shallower.

♦ Debris from floating-leaved plants contributes tothe formation of peat deposits, particularly as thelake becomes shallower over time and aquaticplants grow more abundantly.

♦ If periods of low water are followed by a rapid rise inwater level, the roots of some dead floating-leavedplants (called rhizomes) can float to the surface wherethey block access and cause difficulties with navigation.

♦ In many cases, masses of rhizomes uprooted fromthe bottom can form floating islands called tussocks—becoming so large that trees can grow on them.

♦ In waterbodies where water hyacinths or waterlettuce grow extremely well, these plants maycompletely cover the waterbody’s surface andcause major navigational problems.

☛ See Algae, Eutrophic, Hypereutrophic,Sulfur, and Total chlorophyll.

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Water shield (Brasenia schreberi)

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In Florida:Floating-leaved plants occur in many Florida

waterbodies. If the lake is shallow enough, rootedfloating-leaved plants can grow completely acrossit. In Florida waterbodies where there are extensiveloose sediments, the roots of floating-leaved plantsanchored to the bottom provide a stable surface thatsome species of fish need for successful spawning.

The stems of floating-leaved plants (i.e.spatterdock) often contain burrowing insectscalled bonnet worms that some anglers use forbait. In many Florida waterbodies, certain float-ing-leaved plants are considered a major aquaticweed problem and require constant managementin order to maintain acceptably low levels. Forexample, water hyacinths can grow so denselythat waterways become impassable.

Health Concerns:Floating-leaved plants are not generally

thought of as a human health concern, althoughthey can create problematic situations. Forexample, dense growths of floating-leaved plantscan entangle swimmers. Floating-leaved plantsmay also provide habitat for mosquitoes andanimals like snakes and alligators that may bedangerous under certain conditions.

☛ See Aquatic macrophytes, Emergentplants, and Floating-leaved plant biomass.

☛ See Average plant biomass andBiological productivity.

☛ See Trophic state and each of itscategories: Oligotrophic, Mesotrophic,Eutrophic, and Hypereutrophic.

Floating-leavedplantbiomass(as used by FloridaLAKEWATCH) isthe average weight of fresh, live floating-leavedplants growing in one square meter of a lake’sbottom area. The measurement of floating-leavedplant biomass in a waterbody is one of severalmeasurements that can be used to assess awaterbody’s overall biological productivity.

In Florida:Average floating-leaved plant biomass in

Florida lakes generally ranges from 0 to 19 kg wetwt/m2. It appears to be linked with a waterbody’sbiological productivity. This relationship can besummarized as follows:

♦ in biologically unproductive (oligotrophic) lakes,the average floating-leaved plant biomass is about1.0 kg wet wt/m2;

♦ in moderately productive (mesotrophic) lakes,the average floating-leaved plant biomass is about1.5 kg wet wt/m2;

♦ in highly productive (eutrophic) lakes, theaverage floating-leaved plant biomass is about 2.0kg wet wt/m2; and

♦ in the most highly productive (hypereutrophic)lakes, the average floating-leaved plant biomass isabout 3.0 kg wet wt/m2.

Frequency of occurrence(of an aquatic plant) is an estimate of the relativeabundance of specific aquatic plants. FloridaLAKEWATCH determines the frequency ofoccurrence using the following procedure:

♦ A number of evenly-spaced locations arechosen around a shore (usually 10 per lake, butup to 30 locations in a large lake). Locations areselected so that they will give a reasonablerepresentation of the vegetation present in thewaterbody.

♦ At each location, a visual inventory isperformed in each of three areas — the emergentplant zone, the floating-leaved plant zone, andthe submersed plant zone.

♦ The frequency of occurrence is the percentageof locations at which a particular plant was seen.For example, if ten locations were sampled andthe plant maidencane was seen at four of them,the frequency of occurrence of maidencanewould be 40% (that is, 4 divided by 10, thenmultiplied by 100%).

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Fresh plantweightis the weight of fresh,live plant material thathas been collectedfrom a waterbody andshaken or spun toremove excess water.These plants are consid-ered to be wet becausethey are fresh and full ofinternal moisture. The unit of measure used byFlorida LAKEWATCH is kilograms wet weightper square meter (abbreviated kg wet wt/m2).

Geologic regionis an area with similar soils and underlyingbedrock features. Characteristics of a waterbody’sgeologic region may be responsible for its chemicalcharacteristics and trophic state.

Geology can also have a significant influenceon the shape of a waterbody’s basin — a factorthat affects many of a waterbody’s features.

� See Lake region, Morphometry, andTrophic state.

☛ See Color.

4 Dominance of fish can be evaluated several ways — by measuring “numbersof fish per acre” and/or “weight of fish per acre.” Fish can also be sampledusing one or more of a variety of catch methods. Each combination ofmeasurement and sampling techniques may give different indications ofwhich fish are dominant in a waterbody.

Groundwateris water that is underground. Groundwaters aredistinguished from “surface waters” which are foundon top of the ground. In Florida, groundwater residesat different depths in several regions called aquifers.

Hydraulic flushing rateis the rate at which water in a waterbody is replacedby new water.

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☛ See Limiting environmental factors.

Hypereutrophicis an adjective used to describe the level ofbiological productivity of a waterbody. FloridaLAKEWATCH and many professionals classifylevels of biological productivity using four trophicstate categories — oligotrophic, mesotrophic,eutrophic, and hypereutrophic. Of the fourtrophic state categories, the hypereutrophic state isdefined as having the highest level of biologicalproductivity. The prefix “hyper” means overabundant. Hypereutrophic waterbodies are amongthe most biologically productive in the world.Hypereutrophic waterbodies generally have thecharacteristics described below.

♦ Hypereutrophic waterbodies have extremelyhigh nutrient concentrations.

♦While hypereutrophic waterbodies can bedominated by non-sportfish species (gizzard shadand catfish), they can also support large numbersand large sizes of sportfish including largemouthbass, speckled perch, and bream.4

♦ A hypereutrophic waterbody has either anabundant population of algae or an abundantpopulation of aquatic macrophytes. Sometimes itwill support both.

♦ Hypereutrophic waterbodies dominated byalgae are characterized by having high chlorophyllconcentrations (greater than 40 µg/L). Thesewaterbodies have reduced water clarity, causingSecchi depth readings to be less than 1 meter(about 3.3 feet). In contrast, when aquatic macro-phytes dominate a hypereutrophic waterbody,chlorophyll concentrations will be lower. Secchidepth readings will be greater, mimicking those ofless biologically productive waterbodies.

♦ Regardless of whether a waterbody is plant-dominated or algae-dominated, it will typicallyhave thick sediments on the bottom as decayingplant and/or algal debris accumulates.

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Humic acidsare produced when organic matter such asdead leaves decay. Humic acids can colorwater so that it appears reddish or red-dish-brown, like tea. In some cases, thewater can appear almost black.

Ironis a common element found in the soils of the earth.Iron is abbreviated in the Periodic Table of Elementsas Fe. Iron exists in either ferrous (Fe++) or ferric(Fe+++) forms.

The Role of Iron in Waterbodies:Iron is an essential nutrient for aquatic

plants and algae. In addition, iron performs animportant function in aquatic systems through itsinteraction with another nutrient — phosphorus.Specifically, the presence of iron influenceswhether phosphorus is in a form that can be usedby plants and algae. This relationship alsodepends on whether adequate oxygen is present.

Here’s how it works:

Example 1: when oxygen is present in sufficientamounts in the waterbody —

♦ iron will tend to bind with phosphorus;♦ aquatic plants and algae cannot use phosphorusin this form;♦ the result may be that the growth of aquaticplants and algae is limited.

Example 2: when oxygen is not present insufficient amounts in the waterbody —

♦ iron-phosphorus compounds dissolve;♦ aquatic plants and algae can use phosphorus inthis dissolved form;♦ the result may be that the growth of aquaticplants and algae is increased.

Waterbody managers may try aerating iron-rich waters as a strategy to reduce phosphorusconcentrations in order to limit nuisance aquaticplant and algal growth, hoping for the resultsdescribed in Example 1. This effort may bethwarted, however, if sulfur is plentiful in thewater. Iron has the chemical characteristic ofpreferring to bind with sulfur instead of withphosphorus, when there is adequate oxygenpresent, as with an aerator. Therefore, in aeratedsulfur-rich waters, phosphorus would still beavailable for aquatic plant and algae use, and theexpected decline in aquatic plant and algalgrowth would not be realized.

An understanding of the role iron plays in thephosphorus cycle is a particularly important man-agement tool in waterbodies where the primarysupply of phosphorus is that which is dissolvedfrom the bottom sediments into the water column.In this situation, iron manipulation is one of only afew management strategies that have the potentialto limit phosphorus availability effectively.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadaverage total iron concentrations ranging from 0to 2.4 mg/L. Over 75% of these waterbodies hadtotal iron concentrations less than 0.24 mg/L.The highest concentrations of iron are found inFlorida’s highly colored waterbodies. This is

☛ See Algae, Aquatic macrophytes,Chlorophyll, Fish kill, Secchi depth,and Trophic state.

♦ Hypereutrophic waterbodies may experiencefrequent algal blooms.

♦ Oxygen depletion may also be a common causeof fish kills in these waterbodies.

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Teemingwith life...

Hypereutrophic lakes are often characterizedas being “dead.” However, quite the reverse

is true. To say that a waterbody is hypereutrophicimplies it’s capable of producing and supportingthe greatest abundance of living organisms suchas plants, invertebrates, fish, and wildlife.

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understandable because iron combines readilywith organic molecules (like those that make waterappear tea-colored), probably causing the water tobecome iron enriched.

Health Concerns: Iron is not considered a known threat to

human health. It may, however, be toxic to inverte-brates and fish. Canada has issued a guidelinestating that total iron should not exceed 0.3 mg/L,which is higher than the concentration found inmost Florida lakes. If iron is a cause of toxicity toFlorida’s aquatic organisms, and there is no evidencethat it is, only a few Florida lakes are potentially at risk.

Lake regionis a geographic area in whichlakes have similar geology,soils, chemistry, hydrology,and biological features. In1997, using Florida LAKE-WATCH data and otherinformation, the United States Environmental Protec-tion Agency designated 47 lake regions in Florida,using these similarities as their criteria.

Lakes in an individual lake region exhibitremarkable similarities. However, lakes in one lakeregion may differ significantly from those in adifferent lake region. For example, most lakes inthe New Hope Ridge/Greenhead Slope lake regionin northwestern Florida (in Washington, Bay,Calhoun, and Jackson Counties) tend to have lowertotal nitrogen, lower total phosphorus, lower chloro-phyll concentrations and higher Secchi depths

when compared to other Florida lakes.In contrast, lakes in the Lakeland/Bone Valley

Upland lake region in central Florida (in Polk andHillsborough Counties) tend to have higher totalnitrogen, higher total phosphorus, higher chloro-phyll concentrations and lower Secchi depths,when similarly compared.

Using descriptions of lake regions, reason-able, attainable water management goals andstrategies can be established for individual lakes.

In addition, lakes with water chemistry thatdiffers markedly from that of other lakes in thesame lake region can be identified and investigated todetermine the cause of their being atypical.

The lake regions are mapped and described inLake Regions of Florida (EPA/R=97/127). TheFlorida LAKEWATCH Program can provide a freepamphlet describing:(1) how and why the lake regions project wasdeveloped;(2) how to compare your lake with others in itsLake Region; and(3) how the Lake Region Classification Systemcan be useful to you.

A copy of Lake Regions of Florida can be obtained by contacting the U.S.

Environmental Protection Agency at 200SW 35th Street, Corvallis, OR 97333 andrequesting Publication EPA/R=97/127.A color poster of the Florida Lake Regionscan be obtained from the Florida Departmentof Environmental Protection (Tallahasseephone: 850/921-9918). These sources arevalid as of October, 1999.

Limiting environmentalfactorsare factors whose presence or absence causes thegrowth of aquatic plants and/or algae to be restricted.A few examples are described below.

♦ Suspended solids (tiny particles stirred up frombottom sediments or washed in from the watershed)can reach concentrations high enough that the growthof plants and algae is limited because sunlight isblocked out of the water column. This is a commonsituation in shallow lakes, especially those withheavy wave action like Lake Okeechobee in southFlorida.

♦ The color of dissolved substances, though translu-cent, can block sunlight and retard algal growth.Many of Florida’s lakes are tea-colored (reddish orreddish-brown) because of dissolved organicsubstances in the water. Even when tea-coloredlakes are rich in nutrients, the growth of algae andsubmersed aquatic plants can be limited becausethe colored water prevents sunlight from reaching them.

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☛ See Color and Humic acids.

Limnologyis the scientific studyof the physical,chemical, andbiological character-istics of inland (non-marine) aquaticsystems. It is a multi-disciplinary scienceinvolving botany,chemistry, engineer-ing, fisheries biology,and zoology to fostera better understanding of freshwater systems.A limnologist is a scientist who studies limnology.

♦ Hydraulic flushing rate is the rate at whichwater in a waterbody is replaced with new water. Theflushing rate can influence algal abundance signifi-cantly. Waterbodies with high flushing rates — suchas many of Florida’s springs — have low planktonicalgal levels even though they may have high nutrientconcentrations. This paradoxical condition existsbecause algae are flushed out of the system beforethey have time to grow to their maximum potential.

♦ Aquatic macrophytes should also be consideredas a limiting environmental factor, because theirpresence may limit the growth of free-floating algaein Florida waterbodies indirectly. For example, ifmacrophyte coverage (PAC) is less than 30% of awaterbody, the presence of macrophytes does notappear to influence open-water algal levels. How-ever, lakes with aquatic macrophytes covering over50% of their bottom area typically have reducedalgal levels and clearer water.

One explanation is that either aquatic macro-phytes, or perhaps algae attached to them, use theavailable phosphorus in the water, competing withthe free-floating algae for this necessary nutrient.

Another explanation is that macrophytes anchorthe nutrient-rich bottom sediments in place and bufferthe action of wind, waves, and human effects,preventing re-suspension of nutrients into the watercolumn that can stimulate algal growth.

These same macrophytes act as a third type ofbuffer by preventing wind and wave action fromre-suspending the actual algal cells (and/or othersuspended solids) into the water column. By prevent-ing algal cells from re-entering the water column,the macrophytes (plants) inhibit any further algalgrowth, due to the fact that the algal cells are “lost”in the bottom sediments where they are denied thenecessary light and nutrients required for growth.

Often the management of a waterbody isfocused solely on the manipulation of nutrients as astrategy for controlling growth of algae and/orplants. However, a truly skilled manager will evaluateall the potentially limiting environmental factors andconsider every possibility.

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5 Atlas of Alberta Lakes, 1990. University of Alberta Press,Edmonton, Canada.

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Limiting nutrientis a chemical necessary for plant growth — butavailable in smaller quantities than needed foralgae to increase their abundance. Once thelimiting nutrient in a waterbody is exhausted,algae stop growing. If more of the limitingnutrient is added, larger algal populations willresult until their growth is again limited bynutrients or by limiting environmental factors.

In Florida waterbodies, nitrogen and phospho-rus are most often the limiting nutrients. Aquaticplants may not respond as directly to nutrientlimitation in the water as do algae because many ofthese plants can also take their required nutrientsfrom the bottom sediments, through their roots, aswell as from the open-water.5

In most freshwater lakes in Florida, the limitingnutrient is believed to be phosphorus. However, inwatersheds where soils contain sizeable deposits ofphosphorus, nitrogen will usually be the limitingnutrient. Nitrogen may be the limiting nutrient insome saltwater systems. Less commonly, silica canbe the limiting nutrient in some waters. Tracenutrients (like molybdenum and zinc) that arenecessary for the growth of plants and algae mayalso be in limited supply in some circumstances.

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☛ See Algae, Aquatic macrophytes, Color,Humic acids, and Trophic state.

☛ See Limiting environmental factors,Nitrogen, Phosphorus, and Silica.

Macrophyte

Magnesiumis the eighth most abundant natural element onearth and is a common component of water.Magnesium is found in many geologic formations,including dolomite. It’s an essential nutrient for allorganisms and is found in high concentrations invegetables, algae, fish, and mammals. Magnesium isrepresented in the Periodic Table of Elements as Mg.

The Role of Magnesiumin Waterbodies:

Natural sources contribute more magnesiumto the environment than do all human activitiescombined. Magnesium is found in algal pigments(known as chlorophyll) and is used in the metabolismof plants, algae, fungi, and bacteria. Freshwaterorganisms need very little magnesium comparedto the amount available to them in water. Becausethere is such little biological demand for magnesiumcompounds and because they are highly soluble,magnesium concentrations in waterbodiesfluctuate very little.

Elevated (high) magnesium concentrations, cancause water to be designated as “hard” water.(Elevated calcium concentrations can have thesame affect.) When hard water is used for agri-cultural, domestic, and industrial purposes, acrusty mineral buildup called “scale” can formand cause problems. The scale produced byextremely hard water can clog irrigation linesand water pipes in houses and can reduce theefficiency of hot water heaters.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998, hadaverage magnesium concentrations rangingfrom 0.2 to over 600 mg/L. Magnesium concen-trations are higher in waterbodies whereinflowing water has been in contact withdolomite.

☛ See Calcium (for a description of hard water).

☛ See Water depth.

☛ See Aquatic macrophytes.

☛ See Trophic state.

Mean depthis another way of saying “average water depth.”The mean water depth is measured in either feet ormeters and is designated in scientific publicationsby the letter “z.”

Mean depth can be estimated by measuringthe water depth in many locations and averagingthose values. Individual depth measurements maybe done by using a depth finder (fathometer) or bylowering a weight, at the end of a string or rope,into the water and measuring how far it sinksbelow the surface until it rests on the bottom.

If more accuracy is needed, mean depth shouldbe calculated by dividing a waterbody’s volume byits surface area. This method will usually result in adifferent value than if measured depths are averaged.

Mesotrophicis an adjective used to describe the level of biologicalproductivity of a waterbody. Florida LAKEWATCHand many professionals classify levels of biologicalproductivity using four trophic state categories —oligotrophic, mesotrophic, eutrophic, and hyper-eutrophic. Of the four trophic state categories, themesotrophic state is defined as having a moderatelevel of biological productivity. (The prefix “meso”means mid-range.)A mesotrophic waterbody is capable of producingand supporting moderate populations of livingorganisms (plants, fish, and wildlife).Mesotrophic waterbodies generally have:♦ moderate nutrient concentrations;♦ moderate growth of algae, aquatic macrophytesor both;♦ water clear enough (visibility of 8 to 13 feet) thatmost swimmers are not repelled by its appearanceand can generally see potential underwater hazards.

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Health Concerns:Magnesium causes no known human health

problems. Drinking large amounts of hard waterwhen the body is accustomed to soft water, how-ever, may have a laxative effect.

Morphometry (Morphometric)is the measurement of shapes. Morphometricparameters of a waterbody can be best understoodby looking at a detailed map of the waterbody,preferably a map showing the contours of thebottom (called a bathymetric map). Morphometricparameters of a waterbody also include its meandepth, maximum depth, shoreline length, volume,and size of its basin. These characteristics significantlyaffect all aspects of how a waterbody functions.

Nitrogenis an element that, in its different forms, stimulates thegrowth of aquatic macrophytes and algae in water-bodies. Nitrogen is represented in the PeriodicTable of Elements as N.

Nutrientsare chemicals that algaeand aquatic macrophytesneed for growth. Nitro-gen and phosphorus arethe two most influentialnutrients in Floridawaterbodies. Nutrients inwaterbodies can comefrom a variety of sources.

In most casesnutrients are carriedinto a waterbodyprimarily when water drains through the surround-ing rocks and soils, picking up nitrogen and phos-phorus compounds along the way. For this reason,knowledge of the geology and physiography of anarea can provide insight into how much nutrientenrichment can be reasonably expected in anindividual waterbody from this natural source.

For example, lakes in the New Hope Ridge/Greenhead Slope lake region in northwesternFlorida (in Washington, Bay, Calhoun, andJackson Counties) can be expected to have low

Oligotrophicis an adjective used to describe the level of biologicalproductivity of a waterbody. Florida LAKEWATCHand many professionals classify levels of biologicalproductivity using four trophic state categories —oligotrophic, mesotrophic, eutrophic, andhypereutrophic.

Of the four trophic state categories, theoligotrophic state is defined as having the lowestlevel of biological productivity. (The prefix“oligo” means scant or lacking.)

An oligotrophic waterbody is capable ofproducing and supporting relatively small popula-tions of living organisms (plants, fish, and wildlife).The low level of productivity in oligotrophicwaterbodies may be the result of low levels oflimiting nutrients in the water, particularly nitrogenor phosphorus, or by other limiting environmentalfactors.

Oligotrophic waterbodies generally havethe following characteristics:

♦ Nutrients are typically in short supply, andaquatic macrophytes and algae are less abundant.

♦ Oligotrophic waterbodies typically have less plant

nutrient levels because they are in a nutrient-poorgeographic region. Whereas, lakes in the Lakeland/Bone Valley Upland lake region in central Florida(in Polk and Hillsborough Counties) can be ex-pected to have very high nutrient levels because theland surrounding the lakes is nutrient-rich.

There are many other sources of nutrients,however, and they are generally not as substantialas nutrient contributions from surrounding rocksand soils. Some occur naturally, and others arethe result of human activity. For example nutri-ents are conveyed in rainfall, stormwater runoff,seepage from septic systems, bird and animalfeces, and the air itself. Most nutrients can moveeasily through the environment. They may comefrom nearby woods, farms, yards, and streets —anywhere in the watershed.

☛ See Mean depth.

☛ See Limiting nutrient, Nutrients,and Total nitrogen.

Florida LAKEWATCHvolunteers collect monthlysamples for nutrient analysis.

☛ See Algae, Aquatic macrophytes,Chlorophyll, Lake regions, Limiting nutrients,Total nitrogen and Total phosphorus.

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debris accumulated on the bottom over the yearssince aquatic macrophytes and algae are less abundant.

♦ Oligotrophic waterbodies often tend to havewater clarity greater than 13 feet, due to lowamounts of free-floating algae in the watercolumn. The clarity may be decreased however,by the presence of color (from dissolved sub-stances), stirred-up bottom sediments, orstormwater runoff (particulate matter).

♦ Fish and wildlife populations will generally besmall, because food and habitat are often limited.Oligotrophic waterbodies usually do not supportabundant populations of sportfish such as large-mouth bass and bream, and it usually takes longerfor individual fish to grow in size. Fishing may begood initially if the number of anglers is small, butcan deteriorate rapidly when fishing pressureincreases and fish are removed from the waterbody.

♦ A waterbody may have oligotrophic character-istics even though it has high nutrient levels.This can occur when a factor other than nutrientsis limiting the growth of aquatic macrophytesand algae. For example, a significant amount ofsuspended sediments (stirred-up sediments orparticles washed in from the watershed) ordarkly colored water can retard macrophyte andalgae growth by blocking sunlight.

PACis an abbreviation forpercent area coveredand is a measure of thepercentage of the bottomarea of a waterbody withaquatic macrophytesgrowing on, or over it.Aquatic scientists usePAC to assess the abun-dance and importance ofaquatic plants in a waterbody.

Waterbodies in the Florida LAKEWATCHdatabase analyzed prior to January 1998 had PACvalues ranging from 0 to 100%. PAC values arelinked with the biological productivity (trophicstate) of waterbodies:

♦ In the least productive (oligotrophic) waterbod-ies, PAC values are usually low. In rare cases wherethey are high (occasionally reaching 100%), it isusually because a thin layer of small plants isgrowing along the bottom.

♦ In moderately productive (mesotrophic) andhighly productive (eutrophic) waterbodies, PACvalues are generally greater than those measured inoligotrophic waterbodies, and the average plantbiomass is also greater.

♦ In extremely productive (hypereutrophic) water-bodies dominated by planktonic algae, PAC valuesare often less than 25%. In Florida however, manyhypereutrophic waterbodies contain mostly aquaticmacrophytes, not algae. In these cases, PAC valuesoften tend to be greater than 75%.

Particulatesare any substances in small particle form that arefound in waterbodies, often suspended in the watercolumn. Substances in water are either in particulateform or dissolved form. Passing water through afilter will separate these two forms. A filter will trapmost of the particulates, allowing dissolved sub-stances to pass through.

☛ See Color, Limiting environmentalfactors, Limiting nutrient, Nutrients,Secchi depth, Total nitrogen, Totalphosphorus, Trophic state, andWater clarity.

Looks can be deceiving... Because oligotrophic waterbodies typicallyhave such clear water (Secchi depth readingsgreater than 13 feet), people often mistakenly thinkthese waters are pure and healthy for humanconsumption. Unfortunately, human disease anddeath can be caused by bacteria, pathogens, andother toxic substances that are invisible to thenaked eye. It should not be assumed that anysurface water is safe to drink — no matter howclear it looks. It should also be noted that in Florida,fish having some of the highest levels of mercuryhave been caught in oligotrophic waters.

☛ See Algae, Aquatic macrophyte, Averageplant biomass, and Trophic state.

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☛ See Algae, Biological productivity,Nutrients, Phytoplankton, andWater clarity.

☛ See Water quality (for Florida standards).

☛ See Lake region.

Periphytonare algae attached to underwater objects such asaquatic plants, docks, and rocks. There are severaltypes of periphyton. They’re named according towhere they grow as follows:

♦ epiphytic algae grow on the surface of aquatic plants;♦ epipelic algae are attached to sediments;♦ epilithic algae are attached to rocks; and♦ benthic algae grow along the bottom of a water-body (including epipelic and epilithic algae).

Periphyton communities contribute to alake’s overall biological productivity. Not onlydo they provide food and habitat for fish andinvertebrates, but they can also affect nutrientmovement through the aquatic ecosystem inimportant ways. For example, when periphytonare abundant, they can absorb nutrients from thewater so effectively that the growth of free-floating forms of algae may be restricted.

Periphyton are not typically measured byFlorida LAKEWATCH. Water samples taken byLAKEWATCH volunteers are used to measureonly free-floating algae, called phytoplankton,suspended in the water column.

pHis a scale of numbers from 0 through 14 that is usedto indicate the acidity of a waterbody. Water is saidto be acidic if the pH is below 7, and basic when thepH is above 7. A pH value of 7 is consideredneutral, which means it’s neither acidic or basic.The scientific definition of pH is “the negativelogarithm of the hydrogen ion (H+) concentration.”

It’s important to note that each one of the 14increments on the pH scale represents a ten-foldchange in acidity. For example, lake water with apH of 5.0 is ten times more acidic than lake waterwith a pH of 6.0. Scales used in this manner are“logarithmic” like the Richter scale used fordetermining earthquake intensity.

The Role of pHin Waterbodies:

pH influences aquatic biological systems in avariety of ways. In the early years of the 20thcentury, pH was regarded as the “master variable”and was routinely studied by aquatic scientists in anattempt to understand its complex role. Studieshave established that the pH values in waterbodiesrange from less than 4 to over 10. Waterbodies inthe low end of the pH scale are of particular interestto scientists concerned about the effects of acidrain on aquatic plants, fish, and wildlife.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 had pHvalues ranging from less than 4 to nearly 12.Approximately half of the Florida lakes sampledhave pH values between 5.8 and 7.8.

The location of a waterbody has a stronginfluence on its pH. For example, lakes in theOkefenokee Plains lake region in north Florida (inBaker, Columbia, and Hamilton Counties) tend tohave pH values below 4.8, and lakes in the Lake-land/Bone Valley Upland lake region in centralFlorida (in Polk and Hillsborough Counties) tend tohave values above 7.5.

Fish, plants and wildlife have differentsensitivities to pH. For example, the young ofsome fish species cannot survive in water thathas a pH below 5.0. However, with few excep-tions, lakes with low pH in Florida are able tosupport healthy fish populations.

Most living organisms in Florida systemsappear to be well adapted to acidic conditions,possibly because low pH seems to be a naturally-occurring environmental factor. Consequently,many aquatic scientists do not consider acid rainto be as great a threat to Florida’s waterbodies asit is to those in the northeastern United States.

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Health Concerns:pH is not generally thought of as a known

human health concern. However, when pH is lowerthan 5.0, some people experience eye irritation.

pH is important in municipal drinkingwater supplies. The acceptable range of pH fordrinking water is generally from 6.5 to 8.5. Thisrange, however, is not based on direct healthconcerns, but is primarily based on minimizingthe corrosion and encrustation of metal waterpipes. However, pH can affect drinking watersupplies as described below.

♦ When pH is lower than 6.5 or exceeds 8.5,chlorine in drinking water supplies becomes a lesseffective disinfectant.

♦ When pH is lower than 6.5 or exceeds 8.5,chlorine in drinking water supplies can contributeto the formation of cancer-causing trihalomethanes.

♦ When pH of drinking water is in the acidicrange, it can cause copper pipes and lead solderingin pipes to dissolve.

Phosphorusis an element that, in its different forms, stimulates thegrowth of aquatic macrophytes and algae in water-bodies. Phosphorus is represented in the PeriodicTable of Elements as P.

☛ See Algae and Chlorophyll.

☛ See Common plant name and Scientificplant name.

☛ See Phytoplankton.

☛ See Average plant biomass.

☛ See Frequency of occurrence.

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Physiographic regionis a geographic area whose boundaries encloseterritory that has similar physical geology (i.e., soiltypes, land formations, etc.).

Phytoplanktonare microscopic, free-floatingaquatic plant-like organismssuspended in the water column.They are sometimes calledplanktonic algae or just algae.Though individual phytoplankton are tiny in size,they can have a major influence on a waterbody.For example, phytoplankton abundance oftendetermines how biologically productive a water-body can be; small amounts of phytoplankton often

result in less fish and wildlife. Also, the public isconcerned about the abundance of phytoplankton,because it significantly affects water clarity.

Aquatic scientists assess phytoplanktonabundance by estimating its biomass. This is knownas “relative abundance.” Two common methodsused are: (1) viewing phytoplankton through amicroscope and counting each organism, and (2)measuring chlorophyll concentrations in watersamples. Florida LAKEWATCH uses the chlorophyllmethod because it’s faster and less costly.

Planktonic algae

Plant biomass

Plant frequency (%)

Plant species

Potassiumis an important mineral and a nutrient necessary forplant growth. It’s found in many soils and constitutesa little over 2% of the earth’s crust. Natural sources ofpotassium are numerous in aquatic environments.Man-made sources include industrial effluentsand run-off from agricultural areas. (Potassium isused extensively in crop fertilizers.) Its chemicalsymbol from the Periodic Table of Elements is K.

The Role of Potassium in Waterbodies: Because potassium salts are readily soluble in

water, potassium is found primarily in dissolvedform in waterbodies rather than in particulate form.

The concentration of potassium in naturalsurface water is generally less than 10 mg/L, but

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☛ See Limiting nutrient, Nutrients, andTotal phosphorus.

Salinityis the saltiness of water and is influenced by leachingrock and soil formations, runoff from a watershed,atmospheric precipitation and deposition, andevaporation. It is measured in units of parts perthousand (abbreviated “ppt”). The Atlantic Oceanand the Gulf of Mexico typically have salinity valuesaround 35 ppt, although there is significant variation,particularly in near shore areas. Salinity often tendsto be lower in areas receiving inflows of freshwater,like the mouths of rivers. Salinity often tends to behigher in areas where the evaporation rate is high —in hot, dry climates.

potassium concentrations as high as 100 mg/L canoccur. Potassium is essential to plant and animalnutrition. Because potassium concentrations infreshwaters are generally adequate for meeting thenutritional needs of the biological community,potassium is not usually considered as being alimiting nutrient like phosphorus and nitrogen.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadpotassium levels ranging from 0 to 50 mg/L.Over 75% of these waterbodies had potassiumconcentrations less than 3.2 mg/L. Higher potas-sium concentrations generally occur naturally alongthe coast, because marine waters have higheraverage potassium concentrations than freshwater.If potassium concentrations in a coastal areawaterbody are uncharacteristically high, it mayindicate saltwater is seeping through the groundinto the waterbody, called saltwater intrusion.

Health Concerns:Potassium concentrations at the levels found

in freshwaters cause no known direct or indirecthuman health problems.

PVIis a measure of the percentageof a waterbody’s volumethat contains aquaticmacrophytes. Historically,PVI was an abbreviationfor the phrase percentvolume infested withaquatic plants. Recently ithas become an abbreviationfor the more neutral phrasepercent volume inhabited. Regardless of theterminology, PVI is used to assess the abundanceand importance of aquatic macrophytes in awaterbody.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 had PVIvalues ranging from 0 to 100%. In Florida, PVI valuesare strongly linked with the biological productivity(trophic state) of waterbodies as described below:

♦ In the least biologically productive (oligotrophic)waterbodies, PVI values are generally very low.

♦ In moderately biologically productive (mesotrophic)waterbodies and highly productive (eutrophic)waterbodies dominated by aquatic plants, PVIvalues are higher than those measured in oligotrophicwaterbodies.

♦ Highly biologically productive (hypereutrophic)waterbodies dominated by algae usually have verylow PVI values. Hypereutrophic waterbodiesdominated by aquatic plants, usually have veryhigh PVI values.

☛ See Algae, Aquatic macrophyte, Averageplant biomass, and Trophic state.

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☛ See Limiting nutrient and Particulates.

☛ See Chloride, Sodium, andSpecific conductance.

Secchi depthis a measurement thatindicates water clarity.Traditionally, the transpar-ency or water clarity of awaterbody is measured usingan 8-inch diameter disccalled a Secchi disc – namedfor its inventor, PietroAngelo Secchi. A Secchidisc is usually painted inalternating quadrants ofblack and white, though itcan also be solid white. Acord is attached through the center of the disc andis marked off in intervals, usually in feet or meters.

To measure water clarity, the disc is loweredinto the water to find the depth at which it firstvanishes from the observer’s sight. (Note: if thedisc can still be seen as it rests on the lake bottomor if it disappears into plant growth, the depth atwhich this happens is not considered the Secchidepth.)

☛ See Common plant name and Plant species.

LAKEWATCH uses solid whiteSecchi discs, as shown here.

Scientific plant nameis a name used by scientists to help avoid theconfusion caused by the use of common plantnames, which often tend to be inconsistent.Professionals have assigned a unique scientificname to each plant. Scientific names are usuallybased on Latin or Greek words and are written initalics or underlined. For example, the aquaticplant whose common name is maidencane hasthe scientific name Panicum hemitomon.

A scientific plant name consists of two parts.The first part is called the “family name” or genusand the second part refers to the species. For example,Potomogeton pectinatus is the scientific name of aspecific species of pondweed. Potomogeton is thegenus and pectinatus is the species. Potomogetonillinoensis is a different species of pondweed. Byusing scientific names, containing both genus andspecies, scientists can be very specific.

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Silicais the name for compounds containing silicon incombination with oxygen. Silicon is the secondmost abundant element in the earth’s crust, andsilica is found in all waterbodies. Silica generallyoccurs in freshwaters in both dissolved andparticulate forms. Silicon is represented in thePeriodic Table of Elements as Si and the chemicalformula for soluble silica is H4SiO4.

Although human activities (i.e., fluoridation ofdrinking water and some industrial processes), aresources of silica, even pristine waters contain silicacompounds. Many freshwaters contain less than 5mg/L of silica, while concentrations as high as 4000mg/L have been measured in saline waterbodies.

The Role of Silica in Waterbodies:Silica is considered an essential micronutrient

for microorganisms and diatoms (a type of algae).These organisms use silica to form shells andother protective structures. Diatoms are capable ofusing large amounts of silica, and diatom popula-tions may be limited when silica is in short supply.Silica concentrations in water are affected byseveral mechanisms. For example:

♦ As diatom populations increase, the rate atwhich they pull silica from the water alsoincreases (usually in the Spring). This can resultin a decline of silica concentrations in the water.

♦ Silica is removed from the water column alto-gether when diatoms die and sink to the bottom,forming silica-enriched sediments.

♦ When pH is above 7, the amount of dissolvedsilica in the water column is affected by thepresence of iron and aluminum; either one can reducethe amount of dissolved silica in the water column.

♦ The amount of silica in the water column canincrease when humic compounds (organic sub-stances that make water tea-colored) are present.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 had silicalevels ranging from 0 to about 14 mg/L. Over 75%of these waterbodies had silica concentrations lessthan 2.4 mg/L.

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☛ See Water clarity.

Sodiumis the sixth most abundant element on earth. Sodiumis often associated with chloride; common tablesalt is mostly sodium chloride. Sodium is usedextensively in industrial processes, food processing,and in some water softening devices. Sodium isrepresented in the Periodic Table of Elements as Na.

The Role of Sodiumin Waterbodies:

All waters contain sodium. Sodium is essentialto all animals and some microorganisms and plants.Generally, sodium is not considered a limiting factorfor freshwater organisms, unless sodium concentra-tions reach levels at which freshwater organismscannot survive. As sodium concentrations increase ina waterbody, there can be a continuous transitionfrom freshwater organisms to those adapted tobrackish water and then ultimately, to marine(saltwater) organisms. High sodium concentrationscan be expected in the following:

♦ areas near the coast that receive sodium-enrichedgroundwater from saltwater intrusion;

♦ areas where evaporation is excessive (perhaps inhot and/or dry climates); and

♦ areas receiving human pollution includingagricultural runoff containing fertilizer residues,discharges containing human or animal waste,and backwash from water softeners using thesodium exchange process.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadsodium concentrations which ranged from 1 toover 1100 mg/L. Over 75% of these waterbodieshad sodium concentrations less than 13 mg/L.The higher concentrations of sodium are foundin lakes located near the coast and in lakes wherethe groundwater entering the lakes has been incontact with natural salt deposits.

Specific conductanceis a measure of the capacity of water to conductan electric current. A higher value of conductancemeans that the water is a better electrical conductor.The unit of measure for conductance can beexpressed in two ways:

♦ ♦ ♦ ♦ ♦ microSieman per centimeter of water mea-sured at a temperature of 25 degrees Celsius(abbreviated µS/cm @ 25° C).

♦ ♦ ♦ ♦ ♦ Micromhos per centimeter (abbreviatedmicromhos/cm or µmhos/cm).

The Role of Specific Conductance inWaterbodies:

Specific conductance increases when more ofany salt including the most common one, sodiumchloride, is dissolved in water. For this reason,conductance is often used as an indirect measure ofthe salt concentration in waterbodies. In general,waters with more salts are the more productive ones— except, of course, where there are limitingnutrients or limiting environmental factors involved.

Natural factors can also cause higher conduc-tance values in the open water. For example,drought conditions can increase the salt concen-trations in a waterbody in two ways: (1) droughtcan cause inflowing waters to have higher saltconcentrations, and (2) heat and low humiditycan increase the rate of evaporation in openwater, leaving the waterbody with a higherconcentration of salt.

Because animal and human wastes (sewage,feed lot effluent, etc.) contain salts, the measurementof conductance can be used for the detection ofcontamination. Since most discharges of indus-trial and municipal wastewater directly into lakesin Florida have been stopped, measurements ofconductance are now used in this context prima-rily to detect septic tank seepage along shore-lines. It’s important to keep in mind that elevatedconductance measurements may have variouscauses and do not by themselves prove there iscontamination from human or animal wastes.

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Health ConcernsSilica poses no known threat to human

health at the concentrations found in waterbodies.

☛ See Chloride, Salinity, Surface water, andLimiting nutrient.

Health Concerns:At the concentrations found in freshwaters,

sodium generally causes no known direct threatto human health.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadaverage conductance values that ranged from 11 toover 5500 µS/cm @ 25° C. Over 75% of thesewaterbodies had conductance values less than190 µS/cm @ 25° C.

The location of a waterbody has a stronginfluence on its conductance. For example, lakesin the New Hope Ridge/Greenhead Slope lakeregion in northwestern Florida (in Washington,Bay, Calhoun, and Jackson Counties) tend to haveconductance values below 20 µS/cm @ 25° C.While lakes in the Winter Haven/Lake HenryRidges lake region in central Florida (in Polk County)tend to have values above 190 µS/cm @ 25° C.

Health Concerns:There are no known human health concerns

directly related to specific conductance. In waterswhere human or animal waste contamination issuspected, bacterial tests should be conductedregardless of whether conductivity values are high.

☛ See Water quality (for Florida standards).

☛ See Lake region.

☛ See Biological productivity, Chloride,Limiting environmental factors, Limitingnutrient, Salinity, and Sodium.

☛ See Aquatic macrophytes.☛ See Aquatic macrophytes andSubmersed plant biomass.

Submersed plantsare large plants that grow primarily below thewater’s surface. Eelgrass, hydrilla, and coontail areexamples of submersed plants. Some of theseplants are rooted to the waterbody’s bottom sedi-ments, like eelgrass and hydrilla; while some, likecoontail, are not.

The Role of Submersed Aquatic Plants inWaterbodies:

The importance of having submersed vegeta-tion and the amount of submersed vegetationnecessary to achieve specific management goalsare both subjects of ongoing research and debate atthe present time. In general, submersed aquaticplants perform several functions in waterbodies.Some of them are described below.

♦ Submersed vegetation provides habitat for fish.Many aquatic scientists consider this its most impor-tant role.

♦ Submersed vegetation provides food and habitatfor wildlife populations (fish, ducks, invertebrates).

♦ Submersed vegetation affects nutrient cycles andother chemical cycles in complex ways.

♦ Submersed vegetation can increase water clarity.

♦ Submersed vegetation stabilizes bottom sediments.

♦ Submersed vegetation can increase or decreasedissolved oxygen concentrations, depending on itsabundance and the availability of light.

♦ Submersed vegetation contributes to the filling-inof waterbodies by depositing decayed material thataccumulates on the bottom.

Submersed vegetation provides habitat for fish. Manyaquatic scientists consider this its most important role.

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Submersed plantbiomass(as used by Florida LAKEWATCH) is the averageweight of fresh, live submersed aquatic macrophytesgrowing in one square meter area of a waterbody.The measurement of the average submersed plantbiomass is one of several measurements that canbe used to assess a waterbody’s overall biologicalproductivity and to assess the potential importanceof submersed plants.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 had anaverage fresh weight of submersed plants rangingfrom 0 to over 22 kg wet wt/m2. The biologicalproductivity of a waterbody is strongly related tosubmersed plant biomass. This relationship issummarized as follows:

In Florida:Submersed plants occur in virtually all

Florida waterbodies. In an individual waterbody,the availability of light, water clarity, water depth,and sediment stability affect where submersedplants will grow.

Professional management of aquatic plantsin Florida is extensive, because native and non-native submersed plants can reach nuisancelevels. An abundance of submersed aquaticplants can adversely affect recreational boating,swimming, fishing, and fish populations. Also,some people find submersed aquatic plants to beaesthetically unappealing.

Health Concerns:Submersed plants are not generally consid-

ered a danger to human health, but they cancause problems indirectly in some circum-stances. For example:

♦ submersed plants can camouflage underwaterobjects, obstructing the ability of swimmers andboaters to see potential hazards;

♦ submersed plants can entangle swimmers.

♦ In biologically unproductive (oligotrophic)waterbodies, the average submersed plant biomassis about 0.5 kg wet wt/m2.

♦ In moderately productive (mesotrophic) water-bodies, the average submersed plant biomass isabout 1.0 kg wet wt/m2.

♦ In highly productive (eutrophic) waterbodies, theaverage submersed plant biomass is about 2.0 kgwet wt/m2.

♦ In the most highly productive (hypereutrophic)waterbodies, where algae are not the dominantplants, the average submersed plant biomass isabout 5.0 kg wet wt/m2.

Sulfatesare chemical compounds that contain the elementssulfur and oxygen. They are widely distributed innature and can be dissolved into waterbodies insignificant amounts. The chemical formula forsulfates is SO4

=.There are a variety of diverse sources for

sulfates in waterbodies. Sulfate concentrations ina waterbody are influenced primarily by naturaldeposits of minerals and organic matter in itswatershed. Sulfate is also widely used in industryand agriculture, and many wastewaters containhigh concentrations of sulfate. Acidic rainfall(containing sulfuric acid) is a major source ofsulfate in some waterbodies.

The primary source of sulfate in rain inindustrialized areas is through atmosphericdischarges from power plants that burn sulfur-containing fuels and from certain industries.

The primary source of sulfate in rain innon-industrialized areas is through atmosphericallyoxidized hydrogen sulfide (the chemical symbolfor hydrogen sulfide is H2S) which is producedalong coastal regions by anaerobic bacteria.Volcanic emissions also contribute sulfur to theatmosphere.

☛ See Average plant biomass andBiological productivity.

☛ See Trophic state and each of itscategories: Oligotrophic, Mesotrophic,Eutrophic, and Hypereutrophic.

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The Role of Sulfur in Waterbodies: Sulfate is used by all aquatic organisms

for building proteins. Sulfur changes from oneform to another (known as “cycling”) in quitecomplex ways. Sulfur cycling can influence thecycles of other nutrients like iron and phosphorusand can also affect the biological productivity andthe distribution of organisms in a waterbody.

Bacteria can significantly influence thesulfur cycle in water. For example, under conditionswhere dissolved oxygen is lacking, certain bacteriacan convert sulfate to hydrogen sulfide gas(H

2S). Hydrogen sulfide gas has a distinctive

rotten egg smell, and in high concentrations canbe toxic to aquatic animals and fish.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadsulfate concentrations which ranged from 0 toabout 500 mg/L. Over 75% of these waterbodieshad concentrations of sulfates less than 20 mg/L.

Health Concerns:Sulfates pose no known direct threat to

human health. In some Florida lakes, the decom-position of large deposits of organic matter alongthe shorelines will cause the formation of pocketsof hydrogen sulfide gas in the bottom sediments.On the rare occasion when people step into thesepockets, they can experience a burning sensationon their skin. Florida natives may refer to thesesediments as “hot mud.”

☛ See Biological productivityand Nutrients.

☛ See pH.

☛ See Calcium.

UF/IFAS Center for Aquatic and Invasive Plants

Surfacewateris water found on theearth’s surface. It isdistinguished fromgroundwater whichis found underground.Surface waters include many types of waterbodiessuch as lakes, rivers, streams, estuaries, ponds andreservoirs.

Total alkalinityis a measure of water’s capacity to neutralize acids.Total alkalinity is often abbreviated TALK. The unitof measure for total alkalinity is generally milligramsper liter of total alkalinity as equivalent calciumcarbonate (abbreviated mg/L as CaCO3). Eventhough alkalinity is expressed in units that referencecalcium carbonate, alkalinity levels are not determinedby calcium carbonate alone.

The alkalinity of a waterbody is influenced bythe soils and bedrock minerals found in its water-shed and by the amount of contact the water hashad with them. For example, lakes in limestoneregions, which are rich in calcium carbonate, oftentend to have higher values for alkalinity. Those insandy soil regions, which are poor in calciumcarbonate, often tend to have lower values.

Alkalinity (and its opposite, acidity) canalso be influenced significantly by the presenceof several different substances, for example:

♦ phosphorus (in phosphatic soils and rocks);♦ nitrogen (from ammonia);♦ silica (from silicates);♦ organic acids (like humic acids); and♦ gases (specifically carbon dioxide and hydrogensulfide).

When alkalinity is a concern, it’s generallyrelated to the formation of a crusty accumulation ofcalcium deposits, called scale, in tanks and pipes.

The Role of Alkalinity in Waterbodies:Total alkalinity is a major determinant of

the acid neutralizing capacity (ANC) of water-bodies. High alkalinity waters are often morebiologically productive than low alkalinitywaters. Consequently, total alkalinity was onceused as an indirect measure of a lake’s produc-tivity. In recent years, research has shown thatwaterbodies with low alkalinity levels are moresusceptible to the effects of acidic water inputssuch as acid rain.

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In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 had totalalkalinity concentrations ranging from 0 to over300 mg/L as CaCO

3. Over 75% of these waterbod-

ies had total alkalinity concentrations less than 35mg/L as CaCO

3.

The location of a waterbody has an especiallystrong influence on its total alkalinity concentra-tion. For example, lakes in the Okefenokee Plainslake region in north Florida (in Baker, Columbia,and Hamilton Counties) tend to have total alkalin-ity values of 0 mg/L as CaCO

3. While lakes in the

Tsala Apopka lake region in central Florida (inCitrus, Sumter, and Marion Counties) tend to havevalues above 40 mg/L as CaCO

3.

Health Concerns:There is no known level of total alkalinity

in Florida waterbodies that indicates a threat tohuman health.

Total nitrogenis a measure of all the various forms of nitrogenthat are found in a water sample. Nitrogen is anecessary nutrient for the growth of aquatic plantsand algae. Not all forms of nitrogen can be readilyused by aquatic plants and algae, especially nitro-gen that is bound with dissolved or particulateorganic matter. The chemical symbol for theelement nitrogen is “N,” and the symbol for totalnitrogen is “TN.”

Total nitrogen consists of inorganic andorganic forms. Inorganic forms include nitrate(NO

3- ), nitrite (NO

2- ), unionized ammonia (NH

4),

ionized ammonia (NH3+), and nitrogen gas (N

2).

Amino acids and proteins are naturally-occurringorganic forms of nitrogen. All forms of nitrogen areharmless to aquatic organisms except unionizedammonia and nitrite, which can be toxic to fish.Nitrite is usually not a problem in waterbodies,however, because (if there is enough oxygenavailable in the water for it to be oxidized) nitritewill be readily converted to nitrate.

The Role of Nitrogenin Waterbodies:

Like phosphorus, nitrogen is an essentialnutrient for all plants, including aquatic plants andalgae. In some cases, the inadequate supply of TN inwaterbodies has been found to limit the growth offree-floating algae (i.e., phytoplankton). This iscalled nitrogen limitation, and occurs most com-monly when the ratio of total nitrogen to totalphosphorus is less than 10 (in other words, the TNconcentration divided by the TP concentration is lessthan 10 or TN/TP < 10). TN in water comes fromboth natural and man-made sources, including:

☛ See Lake region.

☛ See Water quality (for Florida standards).

☛ See Nitrogen.

A BetterWay...Chlorophyll measure-ments are useful inassessing the trophicstate of a body of water.However, the use ofchlorophyll measure-ments alone mayproduce misleadingresults; chlorophyllmeasurements don’ttake into account thebiological productivityexpressed in the form of aquatic macrophytes.Assessments that also include aquatic plantabundance would be more accurate, particularlyin waterbodies with significant macrophytepopulations.

☛ See Aquatic macrophytes andChlorophyll.

29

Total chlorophyll is a measure of all types of chlorophyll.The abbreviation for total chlorophyll is TCHL.

☛ See Chlorophyll.

LAKEWATCH volunteersfilter lake water to obtainchlorophyll samples.

♦ air (some algae can “fix” nitrogen — pulling itout of the air in its gaseous form and converting itto a form they can use);

♦ stormwater run-off, including natural run-offfrom areas where there is no human impact (nitro-gen is a naturally-occurring nutrient found in soilsand organic matter);

♦ fertilizers; and

♦ animal and human wastes (sewage, dairies,feedlots, etc.).

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 had totalnitrogen concentrations which ranged from less than50 to over 6000 µg/L. Using these average concentra-tions of total nitrogen from this same database, Floridalakes were found to be distributed into four trophicstates as follows.6

♦ approximately 14% of these lakes (those withTN values less than 400 µg/L) would be classifiedas oligotrophic;

♦ about 25% of these lakes (those with TN valuesbetween 401 and 600 µg/L) would be classified asmesotrophic;

♦ 50% of these lakes (those with TN values be-tween 601 and 1500 µg/L) would be classified aseutrophic; and

♦ nearly 11% of these lakes (those with TN valuesgreater than 1500 µg/L) would be classified ashypereutrophic.

The location of a waterbody has a stronginfluence on its total nitrogen concentration. Forexample, lakes in the New Hope Ridge/GreenheadSlope lake region in northwestern Florida (in Wash-ington, Bay, Calhoun, and Jackson Counties) tend tohave total nitrogen values below 220 µg/L. Whilelakes in the Lakeland/Bone Valley Upland lakeregion in central Florida (in Polk and HillsboroughCounties) tend to have values above 1700 µg/L.

Health Concerns:The concentration of total nitrogen in a water-

body is not a known direct threat to human health. Itis the individual forms of nitrogen that contribute tothe total nitrogen measurement and the use of thewater that need to be considered. For example,nitrate in drinking water is a concern. Drinking waterwith nitrate concentrations above 45 mg/L has beenimplicated in causing blue-baby syndrome in infants.The maximum allowable level of nitrate, a compo-nent of the total nitrogen measurement, is 10 mg/L indrinking water. Concentrations of nitrate greater than10 mg/L generally do not occur in waterbodies,because nitrate is readily taken up by plants andused as a nutrient.

☛ See Algae, Algal biomass, Chlorophyll, Limiting nutrient, and Phytoplankton.

☛ See Lake region.

☛ See Trophic state and each of its categories:Oligotrophic, Mesotrophic, Eutrophic, andHypereutrophic; and Water quality.

6 This distribution of trophic state is based solely on totalnitrogen values without utilizing information on totalphosphorus, chlorophyll, water clarity, or aquaticmacrophyte abundance.

Total phosphorusis a measure of all the various forms of phosphorusthat are found in a water sample. Phosphorus is anelement that, in its different forms, stimulates thegrowth of aquatic plants and algae in waterbodies.The chemical symbol for the element phosphorus isP and the symbol for total phosphorus is TP. Somephosphorus compounds are necessary nutrients forthe growth of aquatic plants and algae. Phosphoruscompounds are found naturally in many types ofrocks. Mines in Florida and throughout the worldprovide phosphorus for numerous agricultural andindustrial uses.

The Role of Phosphorusin Waterbodies:

Like nitrogen, phosphorus is an essentialnutrient for the growth of all plants, includingaquatic plants and algae. Phosphorus in waterbodiestakes several forms, and the way it changes from

30

Judging a lake by its label...Although it’s unreasonable to do so, the trophic state classification of a

waterbody is sometimes used as an indicator of “good” or “bad” quality.

For example, because oligotrophic waterbodies often have very clear

water, they are commonly characterized as being “good.” While typical

eutrophic and hypereutrophic waterbodies, with their pea soup green

water and naturally weedy shorelines, might be seen as being “bad.”

Neither of these characterizations is necessarily fair; the judgement of

the quality of a waterbody should depend on how it is going to be used.

For instance, fish caught in supposedly “good”

oligotrophic waterbodies of Florida have some of the highest concentra-

tions of mercury in the state, making them potentially “bad” sites for

catching a fish dinner. Similarly, so-called “bad” eutrophic and hyper-

eutrophic waterbodies support some of Florida’s most abundant fish and

bird populations, making them, in reality, potentially “good” sites for fishing

and birdwatching.

So, it’s not sufficient to judge the quality of a waterbody by its trophic state alone. Instead, one should consider

what specific qualities are desirable or undesirable based on how you intend to use the waterbody.

☛ See Algae, Limiting nutrient,Phytoplankton, Total nitrogen,Water clarity, and Water quality.

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one form to another (called cycling) is complex.Because phosphorus changes form so rapidly,many aquatic scientists generally assess its avail-ability by measuring the concentration of totalphosphorus rather than the concentration of anysingle form. In some waterbodies, phosphorus maybe at low levels that limit further growth of aquaticplants and/or algae. In this case, scientists sayphosphorus is the limiting nutrient.

For example, in waterbodies having TP concen-trations less than 10 µg/L, waters will be nutrientpoor and will not support large quantities ofalgae and aquatic plants.

There are many ways in which phosphoruscompounds enter waterbodies. The more com-mon ones are described below:

♦ Some areas of Florida and other parts of theworld have extensive phosphate deposits. Inthese areas, rivers and water seeping or flowingunderground can become phosphorus enrichedand may carry significant amounts of phospho-rus into waterbodies.

♦ Sometimes phosphorus is added intentionally towaterbodies to increase fish production by fertilizingaquatic macrophyte and algal growth.

♦ Phosphorus can enter waterbodies inadvertentlyas a result of human activities like landscapefertilization, crop fertilization, wastewater disposal,and stormwater run-off from residentialdevelopments, roads, and commercial areas.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 had totalphosphorus concentrations which ranged from lessthan 1 to over 1000 µg/L. Using these averageconcentrations of total phosphorus from this samedatabase, Florida lakes were found to be distributedinto the four trophic states as follows:7

♦ approximately 42% of these lakes (those withTP values less than 15 µg/L) would be classifiedas oligotrophic;

♦ about 20% of these lakes (those with TP valuesbetween 15 and 25 µg/L) would be classified asmesotrophic;

☛ See Trophic state.

32

☛ See Lake region.

7 This distribution of trophic state is based solely on total phosphorusvalues without utilizing information on total nitrogen, chloropyll, waterclarity, or aquatic macrophyte abundance.

☛ See Trophic state and each of itscategories: Oligotrophic, Mesotrophic,Eutrophic, and Hypereutrophic; andWater Quality. A bum rap...

Because waterbodies with low concentrations of TP(total phosphorus) will have relatively clear water,the public may think their water quality is better thanwaterbodies with higher TP. It’s a misconception,however, that clearer water is intrinisically better thanwater that is less clear. Unfortunately, the associationof clear water with low phosphorus levels has giventhe public the mistaken notion that phosphorus is apollutant.

♦ 30% of these lakes (those with TP valuesbetween 25 and 100 µg/L) would be classified aseutrophic; and

♦ nearly 8% of these lakes (those with TP valuesgreater than 100 µg/L) would be classified ashypereutrophic.

The location of a waterbody has a stronginfluence on its total phosphorus concentration. Forexample, lakes in the New Hope Ridge/GreenheadSlope lake region in northwestern Florida (in Wash-ington, Bay, Calhoun, and Jackson Counties) tend tohave total phosphorus values below 5 µg/L. Whilelakes in the Lakeland/Bone Valley Upland lakeregion in central Florida (in Polk and HillsboroughCounties) tend to have values above 120 µg/L.

Health Concerns:There is no known level of total phosphorus in

waterbodies that poses a direct threat to human health.

Transparency

Trophic stateis defined as “the degree of biological productivityof a waterbody.” Scientists debate exactly what ismeant by biological productivity, but it generallyrelates to the amount of algae, aquatic macrophytes,fish and wildlife a waterbody can produce and sustain.

Waterbodies are traditionally classified intofour groups according to their level of biologicalproductivity. The adjectives denoting each of thesetrophic states, from the lowest productivity level tothe highest, are oligotrophic, mesotrophic,eutrophic, and hypereutrophic.

Aquatic scientists assess trophic state by usingmeasurements of one or more of the following:

♦ total phosphorus concentrations in the water;

♦ total nitrogen concentrations in the water;

♦ total chlorophyll concentrations — a measure offree-floating algae in the water column; and

♦ water clarity, measured using a Secchi disc; and

♦ aquatic plant abundance.

Florida LAKEWATCH professionals basetrophic state classifications primarily on the amountof chlorophyll in water samples. Chlorophyllconcentrations have been selected by LAKE-WATCH as the most direct indicators of biologicalproductivity, since the amount of algae actuallybeing produced in a waterbody is reflected in theamount of chlorophyll present. In addition, FloridaLAKEWATCH professionals may modify theirchlorophyll-based classifications by taking theaquatic macrophyte abundance into account.

☛ See Water clarity.

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☛ See Algae, Biological productivity,Chlorophyll, Eutrophic, Hypereutrophic,Mesotrophic, Nutrients, Oligotrophic, andTrophic State Index (TSI).

Pitfalls of using TSI... Applying words like good, fair, and poor to TSIranges has contributed to the unfortunatemisconception that trophic state is synonymouswith the concept of water quality. While higherTSI values indicate waterbodies with high levelsof biological productivity, this is not necessarily a“poor” condition. This can lead to evaluations that are confus-ing. For example, consider a waterbody with aTSI of 80. Its high TSI rating tells us that the lakehas a high level of biological productivity — acapacity to support abundant populations of fishand wildlife. However, if we use Environmental Protectionstandards (see left column adjacent to this text),the same TSI rating of 80 puts the waterbody in thecategory described as “poor and does not supportuse,” regardless of the fact that it is, in reality, ableto support an abundance of fish and wildlife. Whilethis lake may not be ideal for swimming or diving, itis fully able to support recreational activities such asfishing and bird watching.

8 The Florida Water Quality Assessment 305 (b) Report, 1996.9 In Florida, the Secchi depth parameter is often notincorporated into the TSI calculations because so many ofFlorida’s lakes are darkly colored waters. Also, the FloridaDepartment of Environmental Protection uses only themeasurements of total nitrogen and total phosphorus whenthe concentration of total chlorophyll is not available . If either of the nutrient concentrations is not available,however, FDEP will not calculate the TSI.

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Trophic State Index (TSI)is a scale of numbers from 1 to 100 that can be usedto indicate the relative trophic state of a waterbody.Low TSI values indicate lower levels of biologicalproductivity, and higher TSI values indicate higherlevels. The use of TSI is an attempt to make evalua-tions of biological productivity easier to understand.

Using mathematical formulas, TSI values canbe calculated individually for four parameters: totalnitrogen concentrations, total phosphorus concen-trations, total chlorophyll concentrations, andSecchi depth. Sometimes a single TSI value for awaterbody is calculated by combining selectedindividual TSI values.

The State of Florida classifies waterbodiesaccording to “designated uses” that have beenassigned to each. (See Water Quality in thiscircular for a more detailed description.)

The Florida Department of EnvironmentalProtection (FDEP) assesses water quality inFlorida by evaluating whether each waterbody isable “to support its designated use.” 8 The FDEPassessment is based solely on TSI values as follows:

♦ waterbodies with TSI values from 0 to 59 arerated as “good and fully support use;”

♦ those waterbodies with TSI values between 60 to69 are rated as “fair and partially support use;” and

♦ waterbodies with TSI values from 70 to 100 arerated as “poor and do not support use.”

Individual TSI values may be further combinedin a special type of averaging to produce anAverage Trophic State Index (abbreviated TSIave).

9

Government and regulatory agencies responsiblefor water management often use the average value,overlooking the fact that the designing author,Dr. Robert Carlson of Kent State University inOhio, never intended TSI values to be reduced toa single number. TSI values for individualparameters could differ markedly within anyspecific waterbody, and this significant variationwill be obscured when the TSI

ave is calculated.

Dr. Carlson has noted that TSI values shouldnot be averaged; consideration of the differences inindividual TSI values in a waterbody can provideinsight and a better understanding of its biologicalproductivity.

☛ See Trophic state and Water Quality.

be clear enough so that they can see where theyare going. In Canada, the government recommendsthat water should be sufficiently clear so that aSecchi disc is visible at a minimum depth of 1.2meters (about 4 feet).

This recommendation is one reason thatmany eutrophic and hypereutrophic lakes thathave abundant growths of free-floating algae donot meet Canadian standards for swimming andare deemed undesirable. It should be noted thatthese lakes are not necessarily undesirable forfishing nor are they necessarily polluted in thesense of being contaminated by toxic substances.

The Role of Water Clarityin Waterbodies:

Water clarity will have a direct influence onthe amount of biological production in a water-body. When water is not clear, sunlight cannotpenetrate far and the growth of aquatic plantswill be limited. Consequently aquatic scientistsoften use Secchi depth (along with total phosphorus,total nitrogen, and total chlorophyll concentra-tions) to determine a waterbody’s trophic state.

Water clarity affects plant growth, butconversely, the abundance of aquatic plants canaffect water clarity. Generally, increasing theabundance of submersed aquatic plants to cover50% or more of a waterbody’s bottom may havethe effect of increasing the water clarity.

One explanation is that either submersedmacrophytes (plants), or perhaps algae attachedto aquatic macropyhtes, use the available nutri-ents in the water, depriving the free-floating algaeof them. Another explanation is that the submersedmacrophytes anchor the nutrient-rich bottomsediments in place — buffering the action of wind,waves, and human effects — depriving the free-floating algae of nutrients contained in the bottomsediments that would otherwise be stirred up.

Because plants must have sunlight in orderto grow, water clarity is also directly related tohow deep underwater aquatic macrophytes willbe able to live. This depth can be estimated usingSecchi depth readings.

34

The Florida LAKEWATCH Program doesnot use the TSI system (neither the TSI

ave nor

individual TSI values). Instead LAKEWATCHfinds it more informative to use the individualvalues of the four measured parameters withouttransforming them into TSI values.

☛ See Algae, Humic acids, and Secchi depth.

☛ See Trophic State.

☛ See Trophic State, Water Clarity,and Water Quality.

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Water clarityis the transparency or clearness of water. Whilemany people tend to equate water clarity withwater quality, it’s a misconception to do so.Contrary to popular perceptions, crystal clearwater may contain pathogens or bacteria thatwould make it harmful to drink or to swim in,while pea-soup green water may be harmless.

Water clarity in a waterbody is commonlymeasured by using an 8-inch diameter Secchidisc, attached to a string/rope. The disc is loweredinto the water, and the depth at which it vanishesfrom sight is measured. Measured in this way,water clarity is primarily affected by three com-ponents in the water:

♦ free-floating algae called phytoplankton,

♦ dissolved organic compounds that color thewater reddish or brown; and

♦ sediments suspended in the water, either stirredup from the bottom or washed in from the shore.

Water clarity is important to individualswho want the water in their swimming areas to

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998 hadSecchi depths ranging from less than 0.2 to over11.6 meters (from about 0.7 to 38 feet).

The trophic state of a waterbody can bestrongly related to the water clarity. Using theseaverage Secchi depth readings from the FloridaLAKEWATCH database analyzed prior toJanuary 1998, Florida lakes were found to bedistributed into the four trophic states as follows:10

♦ approximately 7% of the lakes would beclassified as oligotrophic (those with Secchidepths greater than 3.9 meters or about 13 feet);

♦ about 22% of the lakes would be classified asmesotrophic (those with Secchi depths between2.4 and 3.9 meters — or between about 8 to 13 feet);

♦ 45% of the lakes would be classified as eutrophic(those with Secchi depths between 0.9 and 2.4meters — or between about 3 to 8 feet); and

♦ 26% of the lakes would be classified as hyper-eutrophic (those with Secchi depths less than 0.9meters or about 3 feet).

The location of a waterbody has a stronginfluence on its water clarity. For example, lakesin the New Hope Ridge/Greenhead Slope lakeregion (Washington, Bay, Calhoun, and JacksonCounties) tend to have Secchi depths greaterthan 9 feet (3 meters). While lakes in the Lake-land/Bone Valley Upland lake region (in Polkand Hillsborough Counties) tend to have Secchidepths less than 3 feet (0.9 meters).

☛ See Trophic state and each of its categories:Oligotrophic, Mesotrophic, Eutrophic, andHypereutrophic.

☛ See Lake region.

☛ See Mean Depth, PVI (Percent VolumeInfested or Inhabited), PAC (Percent AreaCovered), and Submersed aquatic plants.

☛ See Aquatic macrophytes, Algae,Biological productivity, Chlorophyll, Color,Particulates, Phytoplankton, Secchi depth,Trophic state, and Water quality.

10 This distribution of trophic state is based solely on Secchi depthvalues without utilizing information on nutrient concentrations,chlorophyll concentrations or aquatic macrophyte abundance.

35

Water depthis the measurement of the depth of a waterbodyfrom the surface to the bottom sediments. Waterdepth can vary substantially within a waterbodybased on its morphology (shape). Florida LAKE-WATCH volunteers measure water depth using aweighted Secchi disk attached to a string or cordthat is marked in one -foot increments. Theweighted Secchi disk is dropped down until it hitsbottom and then the distance is determined bymeasuring the length of rope between the bottomand the surface of the water. These measurementsare then recorded for future reference.

Water depth can also be measured using adevice called a fathometer — by bouncing sonicpulses off the bottom and electronically calculatingthe depth. Fathometer readings taken continuouslyalong a number of transects (shore-to-shore tripsacross the waterbody) are used to calculate an averagelake depth. The calculated average lake depth isapproximately the same as the waterbody’s averagewater depth, called mean depth.

Water qualityis a subjective, judgmental term used to describe thecondition of a waterbody in relation to human needs orvalues. The phrases “good water quality” or “poorwater quality” are often related to whether the water-body is meeting expectations about how it can be usedand what the attitudes of the waterbody users are.

Water quality is not an absolute. One personmay judge a waterbody as being high quality, while

☛ See Water quality.

Health Concerns:Water clarity is not known to be directly

related to human health.

36

someone with a different set of values may judge thesame waterbody as being poor quality. For example,a lake with an abundance of aquatic macrophytes inthe water may not be inviting for swimmers but maylook like a good fishing spot to anglers.

Water quality guidelines for freshwaters havebeen developed by various regulatory and govern-mental agencies. For example, the Canadian Councilof Resource and Environmental Ministers (CCREM)provides basic scientific information about theeffects of water quality parameters in severalcategories, including raw water for drinking watersupply, recreational water quality and aesthetics,support of freshwater aquatic life, agricultural uses,and industrial water supply.

Water quality guidelines developed by theFlorida Department of Environmental Protection(FDEP) provide standards for the amounts ofsome substances that can be discharged intoFlorida waterbodies (Florida AdministrativeCode 62.302.530). The FDEP guidelines providedifferent standards for waterbodies in each offive classes that are defined by their assigneddesignated use as follows:

• Class I waters are for POTABLE WATER SUPPLIES;

• Class II waters are for SHELLFISH PROPAGATION ORHARVESTING;

• Class III waters are for RECREATION, PROPAGATIONAND MAINTENANCE OF A HEALTHY, WELL-BALANCEDPOPULATION OF FISH AND WILDLIFE;

• Class IV waters are for AGRICULTURAL WATERSUPPLIES; and

• Class V waters are for NAVIGATION, UTILITY ANDINDUSTRIAL USE.

☛ See Biological productivity, Trophic state,Trophic State Index (TSI), and Water clarity.

Watershedis the area from which water flows into a water-body. Drawing a line that connects the highestpoints around a waterbody is one way to delineatea watershed’s boundary. A more accurate delin-eation would also include areas that are drainedinto a waterbody through underground pathways.In Florida, these might include drainage pipes orother man-made systems, seepage from highwater tables, and flow from springs. Activities ina watershed, regardless of whether they arenatural or man-made, can affect the characteristicsof a waterbody.

Width of emergent andfloating-leaved zone (Average)is an estimate of the average width (in meters orfeet) of the lake zone that is colonized by emer-gent and floating-leaved plants. It’s estimatedfrom the shoreline to the lakeward edge of theplants.

In Florida:Waterbodies in the Florida LAKEWATCH

database analyzed prior to January 1998, hademergent and floating-leaved zone widths thatranged from 0 meters to completely covering awaterbody’s surface. When waterbodies havesignificant coverage by emergent and floating-leaved plants, it would probably be more accurateto call them deep water marshes, instead of lakes.

☛ See Emergent plants and Floating-leaved aquatic plants.

☛ See Recommended Readingat the end of this circular.

All Florida waterbodies are designated asClass III unless they have been specifically classi-fied otherwise (refer to Chapter 62-302.400, FloridaAdministrative Code for a list of waterbodies that arenot Class III ). Excerpts from the FDEP guidelines,including some of the parameters measured byFlorida LAKEWATCH, are shown in the table onpage 37.

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(a) nutrients

FDEP Standards for Class III Freshwaters,partial list (Florida Administrative Code 62.302.530)

Parameter Standard Unit of Measure

Alkalinity Shall not be depressed below 20. mg/L as CaCO3

Chlorides No standard.

micromhos/cmConductance,specific

Shall not be increased more than 50% above backgroundor to 1275, whichever is greater.

Nitrate No standard.

The discharge of nutrients shall continue to be limited as needed toprevent violations of other standards contained in this chapter. Man-induced nutrient enrichment (total nitrogen or total phosphorus) shallbe considered degradation in relation to the provisions ofSections 62.302.300, 62-302,700 and 62.242, F.A.C.

(b) nutrients In no case shall nutrient concentrations of a body of water be altered soas to cause an imbalance in natural populations of aquaticflora or fauna.

pH Shall not vary more than one unit above or below natural back-ground or more than two-tenths unit above or below natural back-ground of open waters, provided that the pH is not lowered to lessthan 6 units or raised above 8.5 units. If natural background is lessthan 6 units, the pH shall not vary below natural background or varymore than one unit above natural background or more than two-tenths unit above natural background of open waters.If natural background is higher than 8.5 units, the pH shall not varyabove natural background or vary more than one unit below naturalbackground or more than two-tenths unit below natural backgroundof open waters.

Transparency Shall not be reduced by more than 10% as compared to thenatural background values.

Depth of thecompensation pointfor photosyntheticactivity.

37

µg/L

µg/L

µg/L

♦ Florida LAKEWATCH Newsletterscontaining educational articles on various topics are available on the Florida LAKEWATCHWeb site at http://lakewatch.ifas.ufl.edu/LWcirc.html or by contacting theLAKEWATCH office and requesting a copy.

♦ Florida LAKEWATCH Data: What Does It All Mean?

♦ Florida Lake Regions: A Classification System

♦ Trophic State: A Waterbody’s Ability to Support Plants, Fish, and Wildlife

♦ Information Circular 101: A Beginner’s Guide to Water Management—The ABCs

♦ Information Circular 102: A Beginner’s Guide to Water Management—Nutrients

♦ Information Circular 103: A Beginner’s Guide to Water Management—Water Clarity

Note: The circulars listed above are only the first three of a series; check with theLAKEWATCH office or Web site for an updated listing.

38

Florida LAKEWATCH publicationsare available by request. Call: 1-800-LAKEWATCH (1-800-525-3928).

Florida-specific Research and Information

Bachmann, M., M.V. Hoyer, and D.E. Canfield, Jr. 1999. Living at the Lake: A Handbook for FloridaLakefront Property Owners. University of Florida, Institute of Food and Agricultural Sciences.Publication SP 247.

Canfield, D.E. Jr., K.A. Langeland, M.J. Maceina, W.T. Haller, J.V. Shireman, and J.R. Jones. 1983.Trophic state classification of lakes with aquatic macrophytes. Canadian Journal of Fisheries andAquatic Sciences. 40: 1713-1718.

Hoyer, M.V. and D.E. Canfield, Jr. 1994. Handbook of Common Freshwater Fish in Florida Lakes.University of Florida, Institute of Food and Agricultural Sciences. Publication SP 160.

Hoyer, M.V., D.E. Canfield, Jr., C.A. Horsburgh, K. Brown. 1996. Florida Freshwater Plants. A Handbook of Common Aquatic Plants in Florida Lakes. University of Florida, Institute of Food andAgricultural Sciences. Publication SP 189.

Recommended Reading

39

Other Relevant Research and Information

Boyd, C.E. 1990. Water Quality in Ponds and Aquaculture. Auburn University, Auburn, Alabama.

Carlson, R.E. 1977. A trophic state index for lakes. Limnology and Oceanography. 22:361-369.

Carlson, R.E. 1979. A review of the philosophy and construction of trophic state indices. p. 1-52. [In] T.E.Maloney (ed.). Lake and Reservoir Classification Systems. U.S. Environmental ProtectionAgency. EPA 600/3-79-074.

Carlson, R.E. 1980. More complications in the chlorophyll-Secchi disk relationship. Limnology andoceanography. 25:378-382.

Carlson, R.E. 1981. Using trophic state indices to examine the dynamics of eutrophication. p. 218-221.[In] Proceedings of the international Symposium on Inland Waters and Lake Restoration.U.S. Environmental Protection Agency. EPA 440/5-81-010.

Carlson, R.E. 1983. Discussion on “Using differences among Carlson’s trophic state index values inregional water quality assessment,” by Richard A. Osgood. Water Resources Bulletin. 19:307-309.

Carlson, R.E. 1984. The trophic state concept: a lake management perspective. p.427-430. [In] Lake andReservoir Management: Proceedings of the Third Annual conference of the North American LakeManagement Society. U.S. Environmental Protection Agency. EPA 440/5-84-001.

Carlson, R.E. 1992. Expanding the trophic state concept to identify non-nutrient limited lakes and reservoirs. pp.59-71 [In] Proceedings of a National Conference on Enhancing the States’ Lake Management Programs.Monitoring and Lake Impact Assessment. Chicago.

CCREM (Canadian Council of Resource and Environment Ministers). 1995. Canadian Water Quality Guidelines.Prepared by the Task Force on Water Quality Guidelines of the Canadian Council of Resource andEnvironment Ministers.

Chamberlin, T.C. 1890 (original printing); 1965 (reprinted). The Method of Multiple WorkingHypotheses.Science. 24: 754-758

Cooke, G.D., E.B. Welch, S.A. Peterson, and P.R. Newroth. 1993. Restoration and Management of Lakesand Reservoirs. Second edition. Lewis Publishers.

Forsberg, C. and S.O. Ryding, 1980. Eutrophication parameters and trophic state indices in 30 Swedishwaste-receiving lakes. Archiv fur Hydrobiologie 88: 189-207.

Ryding, S.O. and W. Rast. 1989. The control of eutrophication of lakes and reservoirs. Man and theBiosphere series, UNESCO, Paris. 314p.

Wetzel, R.G. 1983. Limnology. Second Edition. Saunders College Publishing.