1. Aquatic Ecosystems

2. 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

3. 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

4. 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

5. 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

6. Brackish water: water that is saltier than freshwater but less salty than saltwater, found where fresh water rivers meet saltwater

7. 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

8. 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

9. 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

10. Lakes & Ponds: Life Zones

11. 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

12. 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

13. 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

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

15. 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

16. 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

17. Comparison