Freshwater Ecosystems

Freshwater Ecosystems The organisms that live in an aquatic ecosystem are determined by the water’s salinity. Salinity refers to the amount of dissolved salt that the water contains. The two types of aquatic ecosystems are freshwater and marine ecosystems

Freshwater ecosystems Freshwater ecosystems include lakes, ponds, wetlands, rivers, and streams.

Freshwater contains little or no salt, so it has a LOW salinity Freshwater contains little or no salt, so it has a LOW salinity. Flowing freshwater = rivers and streams Still Freshwater = lakes and ponds

Freshwater Organisms Where organisms live in an aquatic ecosystem depends on sunlight, temperature, oxygen, and nutrients. Organisms are grouped by their location and by their adaptations.

Plankton Plankton make up the first group of aquatic organisms. They are microscopic drifters and cannot swim against currents. They float on the surface and need sunlight to survive.

Phytoplankton Phytoplankton are microscopic plants that drift in freshwater and serve as food for most aquatic ecosystems.

Water Biomes Phytoplankton are important producers in water biomes. They are the first step in many aquatic food chains

Nekton Nekton are free-swimming organisms, such as squid, sharks, penguins, fish and seals.

Benthos Benthos are bottom dwelling organisms, such as mussels and barnacles. Many benthic organisms live attached to surfaces.

Lakes Larger and deeper than ponds Plant growth is limited to the shoreline Sunlight does NOT penetrate to the bottom= no plants after a certain depth!

Lakes and Ponds Sunlight and nutrients influence the type and location of organisms in a pond or lake.

Ponds Small, shallow bodies of water Sunlight penetrates all the way to the bottom Most completely filled with plant material Very high amount of nutrients

Littoral Zone A shallow zone in a freshwater habitat where light reaches the bottom and nurtures plants. Farther from shore, phytoplankton make their own food by photosynthesis. Cattails, reeds, and pond lilies are rooted in the mud underwater. Aquatic life is diverse and plentiful The littoral zone near the shore is rich in nutrients.

Benthic Zone The benthic zone is the bottom layer of a pond or lake. It is so deep and there is too little light for photosysnthesis.

Decomposers and bacteria live in this layer where they feed on dead plants and animals that drop down from above.

Freshwater Wetlands Swamp Marsh Freshwater wetlands are covered by water for part of the year. The two types are marshes and swamps. Swamp Marsh

Marshes contain non-woody plants such as cattails

Swamps contain woody plants such as trees and shrubs.

Environmental Functions of Wetlands Trap and filter sediments, nutrients, and pollutants, which protect lakes, reservoirs, and oceans Reduce flooding and protect farmland and roads Prevent erosion of shorelines Provide spawning grounds and habitats Recreational activities such as fishing and boating

Rivers Water moves slower in a river and debris settles on the bottom. Because of this, rivers tend to have more nutrients and less dissolved oxygen. nutrients and oxygen