Aquatic Ecology Notes

Photic Zone

Aphotic Zone

Intertidal Zone

Coral Reef

Life in Layers Life in most aquatic systems is found in surface, middle, and bottom layers. Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth. Euphotic zone (upper layer in deep water habitats): sunlight can penetrate.

Lakes: Water-Filled Depressions Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of: Littoral zone (near shore, shallow, with rooted plants). Limnetic zone (open, offshore area, sunlit). Profundal zone (deep, open water, too dark for photosynthesis). Benthic zone (bottom of lake, nourished by dead matter).

Littoral Zone A shallow area near the shore, to the depth at which rooted plants stop growing. Ex. frogs, snails, insects, fish, cattails, and water lilies.

Limnetic Zone Open, sunlit water that extends to the depth penetrated by sunlight.

Profundal Zone Deep, open water where it is too dark for photosynthesis.

Lakes: Water-Filled Depressions Figure 6-15

Oligotrophic

Eutrophic

Freshwater Wetlands

Freshwater Inland Wetlands: Vital Sponges Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats. Figure 6-18

Freshwater Inland Wetlands: Vital Sponges Filter and degrade pollutants. Reduce flooding and erosion by absorbing slowly releasing overflows. Help replenish stream flows during dry periods. Help recharge ground aquifers. Provide economic resources and recreation.

Marshes An area of temporarily flooded, often silty land beside a river or lake.

Swamps A lowland region permanently covered with water.

Importance of freshwater wetlands They filter & purify water. Habitat for many animals and plants.

Historical Aspects Developers and farmers want Congress to revise the definition of wetlands. This would make 60-75% of all wetlands unavailable for protection. The Audubon Society estimates that wetlands provide water quality protection worth $1.6 billion per year, and they say if wetlands are destroyed, the U.S. would spend $7.7 billion to $31 billion per year in additional flood-control costs.

Estuaries

Definition A partially enclosed area of coastal water where sea water mixes with freshwater.

Salt Marshes The ground here is saturated with water and there is little oxygen, so decay takes place slowly. It has a surface inlet and outlet, and contains many invertebrates. It is also the breeding ground for many ocean animals. Ex. crabs and shellfish.

Mangrove Forests These are along warm, tropical coasts where there is too much silt for coral reefs to grow. It is dominated by salt-tolerant trees called mangroves (55 different species exist). It also helps to protect the coastline from erosion and provides a breeding nursery for some 2000 species of fish, invertebrates, and plants.                                   

Importance of Estuaries Just one acre of estuary provides $75,000 worth of free waste treatment, and has a value of about $83,000 when recreation and fish for food are included. Prime Kansas farmland has a top value of $1,200 and an annual production value of $600.