Aquatic EcosystemsChapter 7

Environmental Science

Section 7.1Freshwater Ecosystems

Freshwater EcosystemsTemperature, sunlight, oxygen, and

nutrients are factors that determine where organisms live.

A main factor is salinity.Salinity is the amount of dissolved salts the

water contains.

Characteristics of Aquatic EcosystemsPlankton are

organisms that cannot swim; they drift.

Phytoplankton are drifting plants that provide most food.

Zooplankton are drifting animals.

Aquatic OrganismsNekton Benthos

Are free-swimming organisms, like fish, turtles, and whales.

Are bottom-dwelling organisms, such as mussels, worms, and barnacles.

Life in a LakeLakes

Zones of Lake or PondLittoral Zone is near the shore and aquatic life is diverse and abundant.

Littoral Zone is where most plants are found: like reeds and cattails.

Benthic Zone is the bottom of the pond or lake which is inhabited by decomposers, insect larvae, and clams.

How Nutrients Affect LakesEutrophication: an increase in the amount

of nutrients in an aquatic ecosystem.Leads to algal blooms and reduced amounts

of oxygen.Other aquatic organisms suffocate and die.Eutrophication is accelerated by run-off.

Freshwater Wetlands Description of a wetland:Areas of land that are

covered with fresh water for at least part of the year.

They act as filters when they absorb and remove pollutants.

Environmental Functions:

They control flooding by absorbing extra water when rivers overflow.

They provide homes for many species and trap carbon.

Marshes Description of a

marsh:Occur on low, flat

lands and have little water movement.

Attract migratory birds

Salinity varies Adaptations: Organisms adapt to

the range of salinity

Swamps Description of a

swamp:Occur on flat, poorly

drained land, often near streams.

Mangrove trees are found in saltwater swamps.

Many amphibians in freshwater swamps

Alligators are the top predator of swamps

Human Impact on WetlandsMany wetlands were drained and filled in for

development.Example: Florida EvergladesLaws protect wetlands and prohibit wetland

destruction.

Rivers Description of a

river: Headwaters: cold and

full of oxygenFlows downward:

warmer, wider, slower, more vegetation and less oxygen.

Factors that impact a river:

Pollution is killing river organisms

Dams change the river ecosystem.

Time for a reading quiz

Section 7.2Marine Ecosystems

EstuariesDescription of an

estuary:An area in which fresh

water from a river mixes with salt water from the ocean.

It forms a nutrient trap making estuaries very productive.

Adaptations of organisms:

Plant and animals must be able to adapt to changing salinity and water levels.

Threats to Estuaries

Used as solid waste landfills.

Used for building sites

Sewage, industrial waste, and agricultural run-off

Salt Marshes vs. Mangrove SwampsSalt Marshes Mangrove Swamp

Are where rivers deposit their load of mineral-rich mud.

Clams, fish, birds.Nursery for shrimp,

crabs, fishAbsorb pollutants

Mangroves have above ground root systems.

Found in tropical and subtropical zones.

Protect coastline from erosion

Coral ReefsAre limestone ridges

built by tiny coral animals called coral polyps

Highly diverse ecosystems but fragile

Fish, snails, clams, sponges

Shallow, clear tropical seas

Threats to Coral ReefsCan’t get too cold or too hotCoral bleaching leads to coral deathGlobal warming, oil spills, run-off, over-fishing

leading to more coral reef destruction

OceansShallow, coastal

waters is where most ocean life is found

Open ocean is one of the least productive ecosystems (lacks sunlight)

Ocean floor consists of dead organisms, decomposers and filter feeders

Threats to OceansPollution Run-offOverfishingTrawl nets

Arctic and Antarctic EcosystemArctic Antarctic

North PoleMost food comes from

oceanPlankton, fish, birds,

whales, and seals

Only continent not colonized

South PolePlankton is base of food

web.Fish, whales, and

penguins.

Time for reading quiz