Introduction to Freshwater Ecosystems

Sec 1-1 Why Study Freshwater Ecosystems? Over 70% of the earth’s surface is

covered by water. Only 3% of the water on earth is fresh

water. All but 2% is frozen in icecaps. Leaving 1% for us to protect and use.

Importance Drinking water Irrigating food crops Habitats for fish we eat Places of recreation Return water to atmosphere for

water cycle

Water usage In the 1900’s: 2400 liters/day/person In the 1990’s: 9000 liters/day/person Today: 16,562 liters/day/person

Ways we use water Drinking Bathing Agriculture Industry

World water use 70% agriculture 22% industry 8% domestication

Industrialization and irrigation

Reasons for increase of water usage

Humans are removing freshwater faster than the water cycle can replace it.

Freshwater ecosystems are: Dumps for domestic sewage and

industrial wastes Being polluted by agricultural

runoff Being depleted by overuse

Section 1-2 Types of Freshwater Ecosystems

Aquatic Ecosystems

 Freshwater Saltwater

 

Freshwater Ecosystems     Standing waters (lentic)     Flowing waters (lotic) 

Standing waters LENTIC

* Ponds and lakes (all aquatic) * Marshes, carrs, swamps, fens, bogs and sloughs -partially terrestrial -referred to as WETLANDS 

Limnology- study of freshwater

Limnologist-person who studies

freshwater

Pond Shallow body of

water Light can reach

the bottom in most places

Large amounts of vegetation, most of which are submerged.

Lake Deeper than a pond Too deep for light

to reach the bottom in many places

No vegetation in deeper areas of water.

Marsh Very shallow area with no large open areas of water.

Contains soggy land areas or ‘islands’

Mostly vegetation like cattails, reeds, and grasses

Carr Very shallow

area Has drier

‘islands’ Dominated

mostly by shrubs

Swamp

Similar to a carr The difference is

the ‘islands’ have trees on them

Bog Waterlogged

area, also known as peat

Contains acidic water

Vegetation is primarily moss

Fen Waterlogged area Contains neutral or

basic water Vegetation is

primarily sedges, grasses, and mosses

Slough Small lake or

pond Nutrient-rich Located in

low areas of prairies

Sec 1-3 Types of Lotic Waters

Ecologist classify lotic waters by a system called

Stream Orders

Streams with NO tributaries are

First Order Streams

When 2 first order streams join they form a

Second Order Stream

When 2 second order streams join they form

a Third Order Stream

Low order streams are often much cooler than higher order streams (on the same river system)

Reasons: First order streams originate in hilly country (slope is

high = stream speed is high) turbulence causes evaporation of water = cools the stream

Low order streams are small (overhanging trees and plants shield stream from the heat of the sun)

Low order streams get much of their water from springs, sub-surface runoff and the water table (these sources usually contain cool water)

Stream Orders and EcologyTwo main things usually happen as the stream

order increases.

1. The water becomes warmer

2. The stream speed decreases

These two changes cause a gradual change in

ecology of the stream.

Stream Order

Stream speed (m/s)

Stream T (C°)

Stream bottom

Oxygen conc.

(mg/l)

Fish

1st 2.2 12 cobble 11 trout

5th 0.6 27 sand 5 carp

*As you move from the headwaters (source) to the mouth, ecological factors change.

Ecological factors:

1. Geophysical

2. Chemical

3. Biological

Gradually along the stream

= Environmental Gradient

Sec 1-4 Lentic and LoticHow they differ….

Lentic- standing (pond, lake, wetlands)

Lotic- flowing (streams and rivers)

1. Source of oxygen (s) photosynthesis (f) aeration

2. Source of food (s) autotrophic food chains (f) detritus food chains (twigs, leaves and grass) heterotrophic food chains (insects, sm land critters)

3. Adaptations of organisms (s) critters stick in the bottom (f) hold on to rocks in fast water (benthic macroinvertebrates, mayflies, stoneflies etc)