Aquatic Ecosystems Chapter 9 Environmental Science Freshwater Ecosystems

Aquatic Ecosystems Chapter 9 Environmental Science

Freshwater Ecosystems • Lakes and Ponds • Wetlands • Rivers • Factors affecting which organisms live in freshwater ecosystems – – Temperature Sunlight Oxygen Nutrients

Aquatic Ecosystem Organisms • Plankton – Organisms that float near the surface – Two types • Phytoplankton – produce most food for ecosystem • Zooplankton – microscopic animals • Nekton – Free-swimming organisms – Fish, turtles, whales • Benthos – Bottom-dwelling organisms – Mussels, worms, barnacles • Decomposers – Break down dead organisms

Lakes and Ponds • Layers of a Lake – Littoral zone • Top layer near the shore • Nutrient rich • Plants are rooted in mud • Plants make energy from photosynthesis – Depend on sunlight – Benthic zone • Bottom of the lake • Bacteria lives here • No sunlight reaches this layer • Dead organisms are consumed by decomposers

Lakes and Ponds, cont. • Eutrophication – Increase of nutrients – Occurs when a large amount of plant growth in a lake or pond – Increases amount of bacteria – Bacteria uses up oxygen – Eventually not enough oxygen for organisms – Runoff can accelerate eutrophication • Sewage, fertilizers, animal wastes

Freshwater Wetlands • Areas of lands covered in water for at least part of the year • Two types – marshes and swamps • Environmental Functions – Absorb and remove pollutants – Control flooding by absorbing extra water – Provide homes for wildlife – Prevent against erosion – Provide recreational areas for fishing, etc. – Provide breeding grounds for fish and shellfish

Marshes • Occur in low, flat lands • Have little water movement • Plants root in sediment under water – Reeds, rushes, cattails • Water birds have adapted to marshes – Heron – spearlike beak to grab fish – Ducks – flat beak to sift through water for fish • Kinds of marshes according to salinity – Brackish marshes – slightly salty water – Salt marshes – saltier water

Swamps • Flat, poorly drained land near streams • Types of swamps – Mangrove swamps • In warm climates near the ocean (salt water) – Freshwater swamps • Ideal environment for amphibians • Swamps attract birds and reptiles – Wood ducks, alligators

Human Impact on Wetlands • Wetlands were considered wastelands where insects breed – Humans drained the wetlands for this reason • Important roles now recognized – Purifiers for wastewater – Flood prevention – Habitats for wildlife • Most states have laws against the destruction of wetlands

Rivers • Many begin from snow melt in mountains – Cold, full of oxygen, fast moving • River flows down the mountain – Becomes wider, warmer, slower, less oxygen • A river changes depending on the land climate it is flowing through

Life in a River • Mosses – Anchor to rocks with roots called rhizoids • Plankton – Live further down stream in warmer water • Trout and minnows – Live at the headwaters (strong current) • Plants – Some are rooted in the river’s sediment – Leaves will vary in shape depending on river’s current

Rivers in Danger • Industries polluting the water – Kills organisms – Makes fish inedible • Runoff from land – Puts pesticides in the river and sediment • Dams – Change the ecosystem in and around river

Assignment • Page 178 • Section 1 Review • #1 -5

Marine Ecosystems • Coastal Wetlands – Areas covered by salt water for all or part of the time – Many fish and wildlife live here – Absorb excess rain • Helps to avoid flooding problems – Filter out pollutants and sediments – Are recreational areas for boating, fishing, etc

Estuaries • Estuary – Area where fresh water from a river mixes with salt water from an ocean – Currents form here • Cause mud and nutrients to fall to the bottom • Marsh grasses will begin to grow here – Constantly receiving fresh nutrients • Makes it a very productive ecosystem

Plants and Animals of Estuaries • Rooted plants – Sunlight can reach the bottom since water is shallow – Nutrient supply is always high • Plankton live here • Mammals feed on plankton – Dolphins, manatees, seals • Oysters, clams feed on the plants • All organisms that live here can tolerate various levels of salinity

Threats to Estuaries • Ports are built over estuaries – Provides easy access to oceans • Usually populated areas surround an estuary – Waste is dumped in the estuary – Pollutants • Sewage • Industrial waste containing toxic chemicals • Agricultural runoff containing pesticides, fertilizers • Quick Lab – Page 180

Salt Marshes • Develop in estuaries where rivers deposit their • • load of mineral-rich mud Clams, fish, aquatic birds live here Protects young animals when small – – Shrimp Crab Fish When older, they migrate to the sea • Absorbs pollutants • Protect inland areas

Mangrove Swamps • Located along coastal areas of tropical and subtropical zones • Mangrove trees are the main plant • Protects the coastline from erosion • Reduces damage from storms • Many animals use as a breeding grounds • Sometimes filled with waste and destroyed

Rocky and Sandy Shores • Rocky Shores – Many plants anchor to rocks – Many animals live on the rocks • Anemones • Mussels • Sponges • Sandy Shores – Dry out when tide goes out – Tiny organisms live off of plankton – Barrier islands • Land that runs parallel to the shore • Protect the mainland coastal wetlands

Coral Reefs • Limestone ridges built by tiny coral animals called polyps – They secrete skeletons of limestone • Calcium carbonate • Thousands of plants and animals live here – Most diverse ecosystem on Earth • Live in clear, warm salt water • Live in shallow water so sunlight can reach • They are predators that never chase their prey – Stinging tentacles to capture organisms that float by

Disappearing Coral Reefs • Corals die if: – Water becomes too hot or too cold – Fresh water drains into the water near reef – Water is too muddy, polluted or too high in nutrients • Causes of coral reef destruction – – – – – Oil spills Sewage Pesticides Silt runoff Overfishing Careless divers Shipwrecks Ships dropping anchor People breaking off pieces

Oceans • Animals – Phytoplankton • Live where light and nutrients are (shallow water) • Have flagella to keep them from sinking deeper – Zooplankton • Feed on phytoplankton near surface • Examples – Jellyfish – Tiny shrimp – Larvae of fish, oysters, lobsters – Decomposers • Live on bottom of ocean • Consume dead organisms

Threats to the Oceans • Pollution – Industrial waste – Sewage – Plant nutrients (fertilizers, etc. ) • Overfishing and nets – Animals can get tangled in nets and die

Arctic and Antarctic Ecosystems • North and South Poles • Large population of plankton • Many fish eat the plankton • Birds, whales, seals feed on the fish • Fish and seals feed the polar bears • Antarctic is not populated by humans – Mainly used for research purposes