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CHAPTER 4. 4 AQUATIC ECOSYSTEMS
Aquatic ecosystems are dependent on abiotic factors like light, nutrient availability, and oxygen. Aquatic ecosystems are determined mostly by depth, flow, temperature, and chemistry of the overlying water.
FRESHWATER ECOSYSTEMS There are 2 main types of freshwater ecosystems: flowing-water and standing-water. Flowing-water ecosystems – rivers, streams, creeks, and brooks are all examples. All organisms that lives in these areas have ways of handling the flow of the water.
STANDING-WATER ECOSYSTEMS Lakes and ponds are the most common. These systems usually have water that flows in and out and also have water circulating within them. The water circulation helps distribute heat, oxygen, and nutrients throughout the lake or pond. Plankton is commonly found in standing-water ecosystems. Plankton are tiny, free-floating organisms that live in both freshwater and saltwater environments. Phytoplankton (a type of plankton) is an algae that is the base of the aquatic food chain. Zooplankton (another type of plankton) feed on phytoplankton.
FRESHWATER WETLANDS A wetland is an ecosystem that water either covers soil or is present at or near the surface of the soil for at least part of the year. This water may be flowing or standing and fresh, salty, or brackish (mix of fresh and salt water). There are usually many insects, fishes, amphibians, and birds in this area. There are 3 types of wetlands: bogs, marshes, and swamps. Bogs are usually dominated by moss and form in depressions where water collects. Marshes are shallow areas along rivers, usually cattails, rushes, and tall grass like plants are found here. Swamps – look like flooded forests. This area will have shrubs and trees.
ESTUARIES Estuaries – wetlands that form where rivers meet the ocean. This area will have a mix of fresh and salt water and the amount of water here is affected by ocean tides. The main source of food is detritus – tiny pieces of organic material. Animals that feed on detritus are clams, worms, and sponges. Salt marshes – temperate zone estuaries that have salt-tolerant grasses. Mangrove swamps – coastal wetlands that are in tropical regions. They have mangroves that grow there (salt tolerant trees)
MARINE ECOSYSTEMS The marine ecosystem is divided into different zones: photic zones are well-lit upper layer. Algae and producers can grow here. Aphotic zone is permanently dark. Chemosynthetic autotrophs are the only producers here. Marine ecosystems are also divided based on the depth and distance from the shore: intertidal zone, coastal zone, and open ocean.
INTERTIDAL ZONE These have regular and extreme changes in surroundings because of tides coming in and out. A good example is a rocky intertidal zone where starfish, sea anemones, crabs, and mussels are located. These areas have zonation – the horizontal banding of organisms that live in a particular habitat.
COASTAL OCEAN This extends from the low-tide mark to the outer edge of the continental shelf (the shallow border that surrounds the continents). Usually part of the photic zone so photosynthesis can take place here. Kelp forests – are found in coastal oceans and have an enormous amount of brown kelp. There is a giant kelp forest near Monterey. Life here includes snails, sea urchins, sea otters, many fish, seals, and whales.
CORAL REEFS These reefs are in warm, shallow waters in tropical areas. Coral reefs are named for the coral animals that make up this area. These areas that have very diverse life.
OPEN OCEAN Begins at the continental shelf and moves outward. It also ranges in depth. Organisms in the deep ocean are exposed to high pressure, very cold temperatures, and total darkness. There is usually not many nutrients in the water so there is not a lot of photosynthesis that takes place. All different types of fish are found here.
BENTHIC ZONE This is the ocean floor. Animals that live here are sea stars, sea anemones, and marine worms. Animals here do not move around much and usually feed on dead organic material that come from surface waters.