Aquatic Ecosystems

Overview of Chapter 7 Freshwater ecosystems: made up of lakes, rivers, and wetlands Marine Ecosystems: include estuaries, coral reefs, and oceans Aquatic Ecosystems: perform many environmental functions and support many plant and animal species

Characteristics of Aquatic Ecosystems Salinity: the amount of dissolved salts in the water, measured in ppt (parts per thousand) Depth of the water affects the temperature and pressure, determining the types of organisms that can live there. Amount of dissolved oxygen and rate of flow: determines the types of organisms that will be found

Main groups of Aquatic Biomes Saltwater: Salinity is about 30 ppt Largest, most common, and diverse biome in the entire world Phytoplankton are the base of the entire global oceanic food chain They provide 50-85% of the world’s oxygen

Freshwater: Salinity is .5 ppt Most lakes, ponds, rivers, & streams Exceptions: Great Salt Lake in Utah, Mono Lake in California Called “hyper-saline” because the salinity may be up to 40 ppt

Brackish water: water that is saltier than freshwater but less salty than saltwater, found where fresh water rivers meet saltwater https://www.youtube.com/watch?v=ZwuVpNYrKPY

Depth Zones Photic: top layer of water Aphotic: below the photic zone Enough sunlight for photosynthesis to occur Depth of this zone depends on water clarity May be 100 meter deep Aphotic: below the photic zone No sunlight Only found in deep lakes and oceans Benthic: bottom, or floor, of a body of water Found in streams, ponds, & coastal areas in the ocean In shallow waters, sun can penetrate and support plant life

Standing Water Ecosystems Freshwater, most common are lakes & ponds, but also include many types of wetlands No net flow of water in and out, but water circulates through the system to distribute heat, oxygen, and nutrients

Standing Water Ecosystems Physical characteristics are well-defined by: Light: influenced by silt and other material found in water Temperature: varies seasonally with depth Oxygen: may be a limiting factor, especially in summer because decomposition uses oxygen

Lakes & Ponds: Life Zones

Lakes & Ponds: Zones Littoral: surrounds most lakes & ponds Shallow water zone where light reaches the bottom & stimulates rooted plant growth Distribution varies with depth of water Organisms associated with emergent plants: snails, insects, fish, and sponges Limnetic: open water zone Extends as deep as light can penetrate Has plankton and free swimming organisms as well as fish Profundal: below the limnetic zone Depends on organic material from the limnetic zone for energy Benthic: decomposition of dead plants and animals takes place here and uses oxygen

Types of Plankton Plankton: microscopic organisms that float near the surface Live in the water column Incapable of swimming against a current Phytoplankton: go through photosynthesis and are the main producers in most aquatic biomes Zooplankton: animals that feed on phytoplankton and are food for smaller fish

Benthic Organisms Most are scavengers and depend on organic material that settles from the top layers, including decomposers Decomposers: recycle dead plants and animals into chemical nutrients like carbon and nitrogen that are released back into the soil, air and water

Human activities such as road construction, agriculture, logging, mining & construction add silt and nutrients to lakes Added nutrients result in eutrophication

Characteristics of Eutrophic Lake Abundance of nutrients flowing into the lake Heavy growth of algae or other aquatic plants Phytoplankton concentrates near the surface Reduced light penetration Dead and algae and organic debris drift to the bottom and are decomposed, which depletes oxygen there

Characteristics of Oligotrophic Lake Nutrient poor Clear water that appears blue to blue-green Cool temperatures Bottom sediments are mainly inorganic Usually found in areas of coniferous forests

Comparison