Aquatic ecology and Biodiversity

Unit 9- Freshwater environment

9.2. Functions of aquatic ecosystem
Main functions of an ecosystem are recycle of nutrients, energy flow, purification of water, attenuate floods, recharge of ground water and provide verities of microhabitats.
Freshwaters
Freshwater ecosystems cover 0.8% of the earth's surface and contain 0.009% of its total water. They generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the world's known fish species.

Freshwater is naturally occurring water on the earth's surface in ponds, lakes, rivers and streams and underground as groundwater in aquifers and underground streams. Freshwater is characterized by having low concentrations of dissolved salts and other total dissolved solids. Freshwater can be defined as water with less than 5 (ppt) of dissolved salts.

Health of an aquatic environment
Health of an aquatic ecosystem is degraded as result of physical, chemical or biological alterations of the environment.
•Physical alterations - Changes in water temperature, water flow and light availability.
•Chemical alterations - Changes in the loading rates of bio stimulatory nutrients, oxygen
consuming materials and toxins.
•Biological alterations - Introduction of exotic species.
Characteristics of freshwaters
The river ecosystems are characterized by the river bed's, gradient or by the velocity of the current. Fast moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow moving water of pools. Eg. Rivers and streams.