Aquatic Ecosystems

Factors that affect which organisms live in which areas of the water: Temperature Sunlight Oxygen Nutrients Salinity

Three groups of aquatic organisms based on location in the water: Plankton – floaters found near the surface (phytoplankton & zooplankton) Nekton – free-swimmers (fish, whales, turtles, etc.) Benthos – bottom-dwellers & decomposers, some attach to hard surfaces

Section #1: Freshwater Ecosystems

Freshwater Lakes & Ponds (natural and man-made) Littoral Zone nutrient rich found near shore life is diverse & abundant plants are rooted in mud underwater Benthic Zone bottom layer little to no light dead, decaying material decomposers, insect larvae, clams

Littoral vs. Benthic Zones

Eutrophication of Lakes runoff from land increases the amt. of nutrients (excess fertilizers, sewage, animal waste) plants & algae grow quickly (& die) increase in bacteria that feeds on decaying materials (use lots of O2) other organisms needing O2 die from lack of available oxygen

This lake shows signs of eutrophication because of the large number of plants.

Freshwater Wetlands act as filters by removing pollutants from water control flooding by absorbing extra water from overflowing streams & rivers habitat for variety of wildlife, including many migratory birds many fish use the area as spawning grounds recreational use by humans

Location of the large freshwater wetlands in the U.S.

Freshwater Marshes found in areas with low, flat land little water movement mostly in southeastern parts of the US (Florida Everglades – largest) non-woody plants are rooted in the nutrient-rich benthic layer in shallow waters Examples = cattails, reeds, rushes water can also be brackish or salty

Marshes contain mostly grass-like plants.

Freshwater Swamps found near streams where the land is flat and poorly-drained good habitat for amphibians, reptiles, & birds dominated by woody plants like shrubs & water-loving trees Examples = mangrove trees water can also be brackish or salty

Alligators are found in both marshes & swamps

Human Impact on Wetlands once considered wastelands – only good for breeding insects were drained, filled, & cleared for farming or development now protected by federal & state laws some groups are working to restore natural wetlands

Rivers & Streams originate from snow melts in the mountains at headwaters, water is cold, full of O2 & moves swiftly over a shallow riverbed as elevation decreases, the river broadens, water slows, can hold less O2

Different Stages in a River

Life in Rivers & Streams depends on location, current speed, amount of nutrients from runoff, amount of O2 plants in faster currents near the headwaters need to use special root systems called rhizoids to hold onto rocks other plants near a river’s mouth can set roots into the bottom sediment

Life in Rivers & Streams certain species like salmon & trout can only survive in the cold, fast-moving waters that hold lots of O2 fish such as catfish and carp live in the calmer, warmer waters plankton cannot live in the strong currents and are also found in calmer, warmer waters

Rivers in Danger people have used rivers as a way to dispose of waste material (garbage & sewage) for many years industries have dumped hot water, toxins, and other waste materials into the water pesticides, excess fertilizers, motor oil, & antifreeze are washed into rivers from the land

Section #2: Marine Ecosystems

Marine Ecosystems while most freshwater ecosystems are self-contained & separate from other bodies of water like it, marine ecosystems are usually connected to others around the globe located mostly in coastal areas and the open ocean organisms must adapt to changes in salinity, tides, available nutrients

Coastal Wetlands coastal land areas are covered by salt water for all or part of the time includes: estuaries salt marshes mangrove swamps barrier islands

Estuaries an area in which fresh water from a river mixes with salt water from the ocean where the two mix, the denser salt water sinks carrying nutrients to the bottom these nutrients are then used by the producers in shallow areas

Estuaries very productive ecosystems because of the constant influx of nutrients protected from harsh ocean waves by the surrounding land (peninsula) sunlight reaches the bottom in most areas – lots of rooted plants & phytoplankton good place for feeding & reproducing organisms must adapt to constant changes in salinity (tides)

The Chesapeake Bay

Chesapeake Bay Watershed

Estuaries 6 out of 10 of the world’s largest urban areas were built on estuaries problems with dumping waste & filling for development estuaries in these densely populated areas cannot handle the large amounts of pollutants – certain species (like oysters) usually help filter the toxins out of the water, but they can only handle so much

Salt Marshes found along the Atlantic Coast & the Gulf of Mexico develop in estuaries where rivers deposit their load of mineral-rich mud considered a nursery to many species of shrimps, crabs, fishes – they are protected in the marsh when small, then migrate to the open ocean after reaching maturity

Mangrove Swamps located in coastal areas of tropical & subtropical zones dominated by mangrove trees these trees grow partly submerged in the salt water – help cut down on erosion along shorelines & protect the land from storms breeding & feeding grounds

Mangrove Trees

Rocky vs. Sandy Shores rocky shores have more plants than sandy shores Why? sandy shores dry out quickly when the tide goes out, plus not a good place for roots to anchor rocks provide a place for creatures or roots to attach

Barrier Islands long, thin islands that run parallel to the coast protect the mainland & the coastal wetlands from erosion & storms in constant motion – trying to develop this land can lead to problems in the future

Barrier Island off the NY coast

Coral Reefs made of limestone ridges secreted by tiny animals called coral polyps accumulate slowly in tropical seas to form reefs one of the most diverse ecosystems on Earth corals can only survive in warm salt water with plenty of sunlight as corals die, others build up on the skeletal remains

Coral Reefs of the World

Coral Reefs corals cannot chase prey, so they use stinging tentacles to capture small organisms that come too close to the reef provides a habitat for many sea creatures to help restore reefs, some groups have tried to create artificial reefs by sinking old barges & ships (must make sure all hazardous materials are removed first)

Threats to Coral Reefs fragile ecosystem – easily damaged – grows very slowly Corals die when water temp is changed ( or ) there’s too much freshwater water is muddy or cloudy nutrients cause algae to grow out of control & blocks sunlight humans oil spills, dumping sewage damage from ships, anchors, careless divers, people stealing pieces

Oceans average salinity = 35‰ sunlight reaches only the surface layer (to ~330 ft deep) ocean life is concentrated in shallow coastal waters plants can anchor to rocks & received nutrients from river inflow phytoplankton live only where there’s enough nutrients deep layer is always dark & very cold food comes from creatures that die & sink to the ocean floor

Ocean Layers

Ocean Problems pollution & dumping algal blooms from excess nutrients over-fishing poor fishing practices discarding fishing lines

Sea Lion Strangled by Fishing Line

Arctic & Antarctic Regions depend on the ocean for almost all food Arctic rich in nutrients from surrounding landmasses plankton form the base of the food chain for all organisms (penguins, whales, seals, polar bears)