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7.1 Freshwater Ecosystems
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7.1 Freshwater Ecosystems
Characteristics of Aquatic Ecosystems
Factors such as temperature, light, oxygen, nutrients, and the bottom determine which organisms live in which areas of the water. For example, sunlight can only reach a certain distance so most photosynthetic organisms live at or near the surface.
Aquatic organisms are grouped by location and by their adaptations. There are 3 groups of aquatic organisms.
The types of organisms in an aquatic ecosystem is determined by the salinty of the water. *Salinity: the amount of dissolved salt the water contains. this divides the ecosystems into marine and freshwater.
- Plankton: cannot swim against currents so they are drifters. Drifting algae, called phytoplankton, are the food base for most aquatic ecosystems. They are microscopic.
- Large drifting animals like jelly fish are called zooplankton.
- Nekton: free swimming organisms such as fish and whales.
- Benthos: bottom dwellers, such as mussels, worms, and barnacles.
- There are also decomposers which break down dead organisms.
Gentle, slow moving manatees are often called sea cows because they spend their time lazily grazing on aquatic vegetation. In N. America, manatees are found in estuaries, bays, and coastal ecosystems, of places like Florida. They are 3-4m in length and weigh 360-545kg, and can live up to 60 years. Unfortunately, although they have few natural enemies, they are often injured ot killed by boats.
Freshwater Ecosystems includes lakes, ponds rivers, and streams. The also include areas known as *wetland: an area periodically under water. Marine ecosystems include marshes, bays, coral reefs, and oceans.
Manatees live in both fresh and salt water. There are 4 species found in the Atlantic Ocean
Beavers:
Lakes and Ponds
Lakes and ponds can be structured into horizontal and vertical zones.
*Littoral zone: near the shore. Aquatic life is diverse and abundant. Plants such as cattails and reeds are rooted in the mud underwater.
*Limnetic Zone: farther from the shore in open water, no rooted plants.
*Euphotic Zone: area with most sunlight, upper area of lake
*Benthic Zone: the bottom of a pond or lake which is inhabited by decomposers, insect larvae, and clams.