Water is Essential to Life

Importance

Leonardo da Vinci said that “Water is the driver of nature.” Without water, the other nutrient cycles would not exist in their present forms, and current forms of life on earth could not exist.

Water’s Unique Properties There are strong forces of attraction between

molecules of water. Water exists as a liquid over a wide

temperature range. Liquid water changes temperature slowly. It takes a large amount of energy for water to

evaporate. Liquid water can dissolve a variety of

compounds. Water expands when it freezes.

Attraction Between Molecules

The strong forces of attraction between molecules of water.

Hydrogen bondsResult in many distinctive properties

Liquid state

Exists in liquid state over wide range of temperatures:

32° F to 212° F

Without water’s high boiling point,oceans would have evaporated long ago

Heat CapacityWater changes temp very slowly because

it can store heat. This protects living organisms from the shock of abrupt temperature changes.

Heat CapacityAlso moderates earth’s climateWater warms & cools slower than

surrounding land

Universal Solvent:

Water can dissolve a many substances.

• Carry nutrients• flush wastes• distribute particles• facilitate other cycles                                                                     

Universal Solvent

Water can dissolve a wide variety of compounds. This means it can easily become polluted by water-soluble wastes.

Water CycleWater moves through

ecosystems transporting trash and other pollutants

                                                                    

Expansion When Frozen

Ice has a lower density than liquid water. Thus, ice floats on water.

Capillary action

Long narrow columns of water rise through roots to leaves

Surface tension Surface behaves

like an elastic membrane

Chapter 6

Aquatic Biodiversity

Coral Reefs

Coral reefs form in clear, warm coastal waters of the tropics and subtropics. Formed by

massive colonies of polyps and algae

Figure 6-1

Among the oldest, most diverse, most productive ecosystemsMarine equivalent to tropical rain forests

Coral Reefs Help moderate atmospheric temperature by

removing CO2 from the atmosphere.

Act as natural barriers that help protect 14% of the world’s coastlines from erosion by battering waves and storms.

Provide habitats for a variety of marine organisms.

AQUATIC ENVIRONMENTS Saltwater and freshwater aquatic life zones

cover almost three-fourths of the earth’s surface

Figure 6-2

AQUATIC ENVIRONMENTS

Figure 6-3

‣ Abiotic (physical) factors are the influences of the non-living parts of the ecosystem.

Examples include pH, salinity, temperature, turbidity, nutrients, wind speed and direction, humidity, precipitation, water pressure, and light intensity and water quality.

‣ Biotic factors are the influences of the living parts of the ecosystem. Producers and consumers interact as competitors, parasites, pathogens, symbionts, and predators.

Factors Affecting Aquatic Ecosystems

What Kinds of Organisms Live in Aquatic Life Zones?

Aquatic systems contain floating, drifting, swimming, bottom-dwelling, and decomposer organisms. Plankton: important group of weakly swimming,

free-floating biota.• Phytoplankton (plant), Zooplankton (animal),

Ultraplankton (photosynthetic bacteria) Necton: fish, turtles, whales. Benthos: bottom dwellers (barnacles, oysters). Decomposers: breakdown organic compounds

(mostly bacteria).

Phytoplankton & Zooplankton Phytoplankton are an

autotrophic group of weakly swimming, free-floating biota that are producers that support most aquatic food chains. These organisms provide much of the oxygen in the Earth’s atmosphere and include:

Phytoplankton (plant-like organisms and cyanobacteria

Different types of phytoplankton

Krill are one of the most important organisms in aquatic food chains especially for whales.

‣Zooplankton are herbivores that feed on plankton and are, in turn, the food stock for larger consumers like whales. These organisms include:

Krill and small crustaceans

Nekton and Benthos Nekton are larger, actively

swimming consumers usually the top consumers in the aquatic ecosystems and include:

Fish, whales and turtles Benthos are bottom-

dwelling creatures that may be primary consumers or decomposers. These highly diverse organisms may live in tide pools, shelves or the abyss and include:

Barnacles, oysters, lobsters and sea anemones

Sharks and Turtles are nektonic species

Benthos or “depths of the sea” are organisms that live on the ocean floor

Life in Layers

Life in most aquatic systems is found in surface, middle, and bottom layers.

Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth. Euphotic zone (upper layer in deep water

habitats): sunlight can penetrate – photosynthesis.

Ocean Zones Coastal and Euphotic

Zone: Lots of light. From 0 - 200 meters. Photosynthesis takes place here

Bathyal Zone: The dimly lit part of ocean. From 200 - 1500 meters.

Abyssal Zone: Completely dark. Extends to a depth of 4000 to 6000 meters (2.5 to 3.7 miles). Water here is very cold & has little dissolved oxygen.

Benthic Zone(Ocean Floor): Bacteria are common & can survive down to 500 meters below ocean floor.

Abyssal Zone

Fig. 6-5, p. 130

Dar

knes

sTw

iligh

tPh

otos

ynth

esis

Sun

Continental shelf

Estuarine Zone

High tide

Low tide

Coastal Zone

Bathyal Zone

Euphotic Zone

Abyssal Zone

Sea level

Open Sea

Marine Ecosystems The oceans that occupy

most of the earth’s surface provide many ecological and economic services.

Scientists estimate that marine systems provide $21 trillion in goods and services per year – 70% more than terrestrial ecosystems.

Figure 6-4

Fig. 6-4, p. 129

Natural Capital

Climate moderation Food

Animal and pet feed

Pharmaceuticals

Harbors and transportation routes

Coastal habitats for humans

Recreation

Employment

Oil and natural gas

Minerals

Building materials

CO2 absorption

Nutrient cycling

Scientific information

Marine EcosystemsEcologicalServices

EconomicServices

Genetic resources and biodiversity

Habitats and nursery areas

Reduced storm impact (mangroves, barrier islands, coastal wetlands)

Waste treatment

The Coastal Zone: Where Most of the Action Is

The coastal zone: the warm, nutrient-rich, shallow water that extends from the high-tide mark on land to the gently sloping, shallow edge of the continental shelf.

The coastal zone makes up less than 10% of the world’s ocean area but contains 90% of all marine species. Provides numerous ecological and economic

services. Subject to human disturbance.

Reefs Reefs:

Reefs are Marine Protected Areas like national parks and wildlife refuges and have significant economic value because of tourism. Calcium carbonate living systems in warm shallow water where light penetrates, reefs are the habitat for many species.

Loss of reefs removes habitats. Reefs are the food source for marine life, breeding grounds for fish and bird species, and shelter and hiding place for many species.

The loss of biodiversity or richness could cause the extinction or decrease in populations of marine organisms.

Reefs serve as a buffer and protection for coastal areas from waves and storms, which could lead to destruction of coastal habitats or the erosion of shoreline habitats.

Reefs are a major carbon sink in the ocean and this carbon storage would be lost.

Sea Grass and Kelp Kelp (Seaweed):

Brown algae groups that provide habitats and food for many organisms. Overfishing leads to the degradation of kelp forests as the herbivores are released from the potential predators. (Sea otter and the urchin.)

Kelp is being considered as a renewable resource because it is fast growing and yields large amounts of methane. The fast growing algae has been the topic of renewable energy talks because of the lack of an irrigation requirement.

Seagrass:Seagrass is highly adaptable and serves as a producer for many marine ecosystems. Seagrass can reduce erosion and increase sedimentation through roots that stabilize the seabed.

These coastal seagrass zones provide shelter for organisms, wave protections, oxygen production and carbon storage.

Estuaries

Estuaries: Definition

A partially enclosed area of coastal water where sea water mixes with freshwater.

Estuaries and Coastal Wetlands: Centers of Productivity

Estuaries include river mouths, inlets, bays, sounds, salt marshes in temperate zones and mangrove forests in tropical zones.

Figure 6-7

Estuaries Estuaries are a partially enclosed

area of coastal water where sea water mixes with freshwater and are constantly changing.

Salinity, temperature, suspended solids, storms (precipitation), and tidal cycles fluctuate with the time of year.

The organisms that live in this unique habitat must be able to tolerate these conditions.

Nutrients that are transported from rivers brings a high amount of nutrients.

This allows a place of breeding for many ocean species and thus makes estuaries highly productive and fertile supporting complex food webs.

Estuary Ecosystem Services Estuaries serve as a carbon sink by absorbing large amounts of

CO2 (sink) and they also serve as filters for pollutants by trapping sediments and pollutants.

They act as sponges as they absorb water recharging groundwater stores and controlling flooding by slowing flow of water.

Economically wetlands are important as well:Provide employment and recreational income through fishing, recreation, and photography.Allow for protected waterway passage between rivers and oceans.Protect property by buffering shores form flow of water and erosion.Treat sewage and storm water that would otherwise be paid for by the local community.

Coastal ecosystems can easily be affected by rising sea levels, storms, temperature change, and rate of water cycling.

Estuaries and Coastal Wetlands: Centers of Productivity

Estuaries and coastal marshes provide ecological and economic services. Filter toxic pollutants, excess plant nutrients,

sediments, and other pollutants. Reduce storm damage by absorbing waves

and storing excess water produced by storms and tsunamis.

Provide food, habitats and nursery sites for many aquatic species.

Salt Marshes The ground here is saturated with water and

there is little oxygen, so decay takes place slowly. It has a surface inlet and outlet, and contains many invertebrates. It is also the breeding ground for many ocean animals. Ex. crabs and shellfish.

Mangrove Forests

Are found along about 70% of gently sloping sandy and silty coastlines in tropical and subtropical regions.

Figure 6-8

Mangrove Forests These are along warm, tropical

coasts where there is too much silt for coral reefs to grow. It is dominated by salt-tolerant trees called mangroves (55 different species exist). It also helps to protect the coastline from erosion and provides a breeding nursery for some 2000 species of fish, invertebrates, and plants.

                                  

Importance of Estuaries

Just one acre of estuary provides $75,000 worth of free waste treatment, and has a value of about $83,000 when recreation and fish for food are included.

Prime Kansas farmland has a top value of $1,200 and an annual production value of $600.

Mouth of river carrying erosion

‣ Ocean margin plants, e.g. intertidal seaweeds and mangroves, must cope with high salt content in the water and changing tidal conditions.

‣ Sea level rise may change these areas, leading to a loss in species.

‣ Construction, building, roads and other residential, commercial, and industrial projects may have a negative impact.

Ocean Margin Plants

Some mangrove species take in brackish water and excrete the salt through glands in the leaves.Seaweeds

growing in the intertidal zone tolerate exposure to the drying air every 12 h.

Mangrove pneumatophores

Rocky and Sandy Shores: Living with the Tides

Organisms experiencing daily low and high tides have evolved a number of ways to survive under harsh and changing conditions. Gravitational pull by moon and sun causes tides. Intertidal Zone: area of shoreline between low

and high tides.

Rocky and Sandy Shores: Living with the Tides

Organisms in intertidal zone develop specialized niches to deal with daily changes in: Temperature Salinity Wave action

Figure 6-9

Fig. 6-9, p. 132

Rocky Shore BeachSea star Hermit crab Shore crab

AnemoneSea urchin

Sculpin

Nudibranch

Low tide

Monterey flatworm

Kelp Sea lettuce

Barnacles

Mussel

Periwinkle

High tide

Fig. 6-9, p. 132

Barrier Beach

Peanut worm

Beach flea

TigerBeetle

DwarfOlive

Clam

High tide

GhostShrimpMole

Shrimp

Sandpiper

Moon snailSand dollarWhite sand

macoma

Blue crab

Low tideSilversides

Barrier Islands

Low, narrow, sandy islands that form offshore from a coastline.

Primary and secondary dunes on gently sloping sandy barrier beaches protect land from erosion by the sea.

Figure 6-10

Effects of Human Activities on Marine Systems: Red Alert

Human activities are destroying or degrading many ecological and economic services provided by the world’s coastal areas.

Threats to Coral Reefs:Increasing Stresses

Biologically diverse and productive coral reefs are being stressed by human activities.

Figure 6-11

Fig. 6-12, p. 135

Ocean warming

Soil erosion

Algae growth from fertilizer runoff

Mangrove destruction

Bleaching

Rising sea levels

Increased UV exposure

Damage from anchors

Damage from fishing and diving

Natural Capital Degradation

Coral Reefs

Bleached CoralBleached coral reef that has lost most of its algae because of changes in the environment (such as cloudy water, too warm temperatures, acidification). With the algae gone, the white limestone of the coral skeleton becomes visible. If the environmental stress is not removed and no other algae species fill the abandoned niche, the corals die.

Ocean Acidity The ocean acts as a CO2 sink, absorbing much of the CO2

produced by the burning of fossil fuels. CO2 reacting with water forms carbonic acid through the

chemical reaction: CO2 + H2O H2CO3

An increase in carbonic acid levels is causing the pH of the oceans to fall. This has major implications for marine life.

50510152025

8.4

8.3

8.2

8.1

8.0

7.9

7.8

7.7

7.6

pH o

f oce

an s

urfa

ce

Time (millions of years before present)

8.3

8.2

8.1

8.0

1850 1900 1950 2000 2050 2100

7.8

7.9

Possible pH range

Effect of Ocean Acidification

Atmospheric carbon dioxide

CO2

Carbonic acidH2CO3

Water H2O

+Bicarbonate

ionsHCO3-

Hydrogen ionsH+

Carbonate ions from the sea

CO32-

+

Deformed shells

Dissolved carbon dioxide

CO2

‣ Because the oceans are naturally alkaline,acidification will not produce acid waters.

‣ Shells will not dissolve but organismswill find it more difficult to gain the CO3

2- ionsneeded to make shells.

‣ Shell making organisms are able to useCO3

2- but cannot use HCO3-.

‣ Acidification lowers the amount of CO32- available.

Ocean pH pH is a logarithmic scale, so even a small pH change

represents a large change in H+. Thus a pH of 5 is 100x more acidic than a pH of 7.

Some areas are affected by pH change more than others. Changes may be due to:

higher human activity, e.g. sea traffic in the North Seanatural processes that affect CO2 uptake, e.g. underwater eruptions

Image: Plumbago using GLODAP data

Amount of change in ocean surface pH since 1900

-0.12 - 0.1 - 0.08 - 0.06 - 0.04 - 0.02 0 (or no data)

Change of -0.07 pH units

Effects Oceans and seas are now being affected by an increase in global mean atmospheric temperature which can cause a rise in sea level.

Melting glaciers, continental ice caps, and melting ice sheets (Greenland and Antactica) causes the amount of water in the ocean to increase.

Thermal expansion of the ocean causes the warm water molecules to move farther apart, increasing the volume of the ocean.

Nutrients, Oxygen & Upwelling Ocean currents are the result

of upwelling and water density. The Grand Banks of the North

American continental shelf. The shape of the deep sea-floor causes nutrient rich water to well up to the surface and the relatively shallow plateau allow a huge range of fishes to proliferate.

The Grand Banks have been fished since the fifteenth century but continual over fishing has devastated many fish stocks.

Nova S

cotia

Newfoundland

Grand Banks

Labrador Current

CANADA

Stre

am

Gulf

Freshwater Ecosystems

FRESHWATER LIFE ZONES

Freshwater life zones include: Standing (lentic)

water such as lakes, ponds, and inland wetlands.

Flowing (lotic) systems such as streams and rivers.

Figure 6-14

Natural Capital

Fig. 6-14, p. 136

Food

Drinking water

Irrigation water

Hydroelectricity

Transportation corridors

Recreation

Employment

Climate moderation

Nutrient cycling

Waste treatment

Flood control

Groundwater recharge

Habitats for many species

Genetic resources and biodiversity

Scientific information

EconomicServices

Freshwater SystemsEcologicalServices

Natural Capital

Thermal Stratification

Lakes: Water-Filled Depressions

During summer and winter in deep temperate zone lakes the become stratified into temperature layers and will overturn. This equalizes the temperature at all depths. Oxygen is brought from the surface to the lake

bottom and nutrients from the bottom are brought to the top.

Definition

The temperature difference in deep lakes where there are warm summers and cold winters.

Lakes: Water-Filled Depressions

During summer and winter in deep temperate zone lakes the become stratified into temperature layers and do not mix

Thermocline

The middle layer that acts as a barrier to the transfer of nutrients and dissolved oxygen.

Overturn

Happens in fall and spring Waters at all level mix

This equalizes the temperature at all depths. Oxygen is brought from the surface to the lake

bottom and nutrients from the bottom are brought to the top.

Causes

During the summer, lakes become stratified into different temperature layers that resist mixing because summer sunlight warms surface waters, making them less dense.

Fall Turnover

As the temperatures begin to drop, the surface layer becomes more dense, and it sinks to the bottom. This mixing brings nutrients from the bottom up to the surface and sends oxygen to the bottom.

Spring Turnover

As top water warms and ice melts, it sinks through and below the cooler, less dense water, sending oxygen down and nutrients up.

Upwelling: Spring and Fall During summer and winter in deep

temperate zone lakes and oceans become stratified into temperature layers. The thermocline allows exchanges nutrients and temperatures and this exchange is called upwelling or turnover and occurs because of the different densities of water.

The equalizing temperature occurs at all depths so that there is a distribution of heat

During the nutrient exchange, oxygen is brought from the surface of the lake or ocean to the bottom and cold nutrient-rich water from the bottom will rise to the surface.

Spring and Fall Turnover

Lakes: Water-Filled Depressions

Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of: Littoral zone (near shore, shallow, with rooted

plants). Limnetic zone (open, offshore area, sunlit). Profundal zone (deep, open water, too dark for

photosynthesis). Benthic zone (bottom of lake, nourished by dead

matter).

Lakes: Water-Filled Depressions

Figure 6-15

Fig. 6-15, p. 137

Pond snail

Benthic zone

Profundal zone

Limnetic zone

Sunlight

Blue-winged teal

Muskrat

Plankton

Bloodworms Northern pikeYellow

perch

Diving beetle

Littoral zone

Painted turtleGreen

frog

Effects of Plant Nutrients on Lakes:

Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support. Oligotrophic (poorly nourished) lake: Usually

newly formed lake with small supply of plant nutrient input.

Eutrophic (well nourished) lake: Over time, sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth.

Oligotrophic Lake

Newly formed lake Nutrient poor Deep, steep banks Glacier & mountain stream fed Crystal clear water Low productivity Small pop of fish & and

other life

Eutrophic Lake Over time sediments, organic matter, & inorganic

nutrients wash into the lake Nutrient rich Murky water, poor visibility Shallow High productivity Lots of plant/fish life

Effects of Plant Nutrients on Lakes:Too Much of a Good Thing

Cultural eutrophication: Human inputs of nutrients from the

atmosphere and urban and agricultural areas can accelerate the eutrophication process.

This can cause algae blooms, decreased productivity, decreased dissolved oxygen, and fish kills when the algae die and decompose

Flowing Water Ecosystems

Because of different environmental conditions in

each zone, a river is a system of different ecosystems.

Fig. 12-11, p. 267

• Deliver nutrients to sea to help sustain coastal fisheries

• Deposit silt that maintains deltas

• Purify water

• Renew and renourish wetlands

• Provide habitats for wildlife

Natural Capital

Ecological Services of Rivers

Freshwater Streams and Rivers:From the Mountains to the Oceans

Water flowing from mountains to the sea creates different aquatic conditions and habitats.

Figure 6-17

Fig. 6-17, p. 139

Source Zone

Rain and snow

Lake GlacierRapids

WaterfallTributary

Flood plain Oxbow lake

Salt marshDelta Deposited

sedimentOcean

SedimentWater

Floodplain Zone

Transition Zone

Freshwater Streams and Rivers Watershed or drainage basin

Area that supplies runoff Small streams join to form rivers Begin in higher elevation – mountains Rain or melting snow

Three Zones Source Transition Floodplain

Source Zone: Headwater A narrow zone of cold, shallow, clear, swiftly flowing water

with waterfalls and rapids. Turbulent, large amounts of dissolved oxygen Cold water fish are also present. Ex. trout. Low nutrient, phytoplankton, & productivity Fish & animals flat, muscular, live under rocks, fight current Plants & algae attach to rocks

Transition Zone Streams merge to form wider, deeper Gentle slopes with fewer obstacles lower dissolved oxygen Supports more producers (phytoplankton) Cloudy Slower flow Warmer

Floodplain: Downstream Wide, deep rivers flow across broad, flat valleys. Rich farm land Higher temp Provide habitat Less dissolved O2

Slow moving water Absorb flood water Large pop of plants & algae Erosion & runoff cause murky water with high levels of

suspended particulates (silt) Mouth of river divides into many channels – Delta –

built up as silt is deposited

Case Study:Dams, Wetlands, Hurricanes,

and New Orleans Dams and levees have been built to control

water flows in New Orleans. Reduction in natural flow has destroyed

natural wetlands. Causes city to lie below sea-level (up to 3

meters). Global sea levels have risen almost 0.3 meters

since 1900.

Freshwater Wetlands

Freshwater Inland Wetlands: Vital Sponges

Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats.

Figure 6-18

Freshwater Inland Wetlands: Vital Sponges

Filter and degrade pollutants. Reduce flooding and erosion by absorbing

slowly releasing overflows. Help replenish stream flows during dry

periods. Help recharge ground aquifers. Provide economic resources and recreation.

Inland Wetlands Inland wetlands are defined by their water quality, soil

type, and species composition.

Wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats. They also filter and degrade pollutants.

Wetlands replenish stream flows during dry periods and recharge ground aquifers. If ground water is being depleted then saltwater intrusion may occur.

Freshwater W

etlandWetlands provide many ecosystem services

Marshes

An area of temporarily flooded, often silty land beside a river or lake.

Swamps

A lowland region permanently covered with water.

Hardwood Bottomland Forest

An area down by a river or stream where lots of hardwoods, like oaks, grow.

Prairie PotholesThese are depressions that hold water out

on the prairie, especially up north in Canada. It is a very good duck habitat.

Peat Moss BogA wet area that over time fills in (the last

stage of succession is peat moss). It can be very deep. In Ireland, they burn peat moss for wood.

Importance of freshwater wetlandsThey filter & purify water.Habitat for many animals and

plants.Since 1600s, over half of US

wetlands have been drained & converted to farmland

Historical Aspects Developers and farmers want Congress to

revise the definition of wetlands. This would make 60-75% of all wetlands unavailable for protection. The Audubon Society estimates that wetlands provide water quality protection worth $1.6 billion per year, and they say if that wetlands are destroyed, the U.S. would spend $7.7 billion to $31 billion per year in additional flood-control costs.

Impacts of Human Activities on Freshwater Systems

Dams, cities, farmlands, and filled-in wetlands alter and degrade freshwater habitats.

Dams, diversions and canals have fragmented about 40% of the world’s 237 large rivers.

Flood control levees and dikes alter and destroy aquatic habitats.

Cities and farmlands add pollutants and excess plant nutrients to streams and rivers.

Many inland wetlands have been drained or filled for agriculture or (sub)urban development.

Human Effects on Aquatic Systems

Most water used by humans comes from rivers, lakes, & aquifers.

Damming rivers for electricity affects water flow downstream as seen in the James Bay project in Quebec with over 600 dams blocking 19 rivers.

Irrigation and diversions for drinking water displace vast amounts of the water for these resource stores.

Pollution from fertilizers, waste, an sewage can have paralyzing effects on rivers, lakes, and oceans.

These actions can have dramatic effects on the habitats and can cause loss of biodiversity.

Irrigation can move move millions of liters of water from rivers and aquifers, affecting land down stream.

Damming and diverting rivers lowers the availability of water downstream and stops annual floods that

replace soil nutrients.

Dams, locks and other obstacles make it very difficult for migratory fish to find their way to breeding grounds.

Impacts of Human Activities on Freshwater Systems

These wetlands have been ditched and drained for cropland conversion.

Figure 6-19