AQUATIC ECOSYSTEMS
Aquatic ecosystems refers to plant and animal communities ocuring in water bodies. Aquatic ecosystems are classified on the basis of salinity into following two types:
(i) Freshwater
(ii) Marine
(i) Freshwater
(ii) Marine
Fresh water ecosystem
Water on land which is continuously cycling and has low salt content is known as fresh
water and its study is called limnology.
(i) Static or still water (Lentic) e.g. pond, lake, bogs and swamps.
(ii) Running water (Lotic) e.g. springs, mountain brooks, streams and rivers.
water and its study is called limnology.
(i) Static or still water (Lentic) e.g. pond, lake, bogs and swamps.
(ii) Running water (Lotic) e.g. springs, mountain brooks, streams and rivers.
Physical characteristics: Fresh waters have a low concentration of dissolved salts.
The temperature shows diurnal and seasonal variations. In tropical lakes, surface temperature never goes below 400C, in temperate fresh waters, never goes above or below 40C and in polar lakes never above 40C.
• In temperate regions, the surface layer of water freezes but the organisms survive
below the frozen surface.
• Light has a great influence on fresh water ecosystems. A large number of suspended
materials obstruct penetration of light in water.
• Certain animals float up to water surface to take up oxygen for respiration Aquatic
plants use carbon dioxide dissolved in water for photosynthesis.
• Lakes and ponds are inland depressions containing standing water. The largest lake in the world is lake Superior in NorthAmerica. Lake Baikal in Siberia is the deepest.
Chilka lake of Orissa is largest lake in India.
Three main zones can be differentiated in a lake:-
• Peripheral zone (littoral zone) with shallow water.
• Open water beyond the littoral zone where water is quite deep.
• Bentic zone (bottom) or the floor of the lake
The temperature shows diurnal and seasonal variations. In tropical lakes, surface temperature never goes below 400C, in temperate fresh waters, never goes above or below 40C and in polar lakes never above 40C.
• In temperate regions, the surface layer of water freezes but the organisms survive
below the frozen surface.
• Light has a great influence on fresh water ecosystems. A large number of suspended
materials obstruct penetration of light in water.
• Certain animals float up to water surface to take up oxygen for respiration Aquatic
plants use carbon dioxide dissolved in water for photosynthesis.
• Lakes and ponds are inland depressions containing standing water. The largest lake in the world is lake Superior in NorthAmerica. Lake Baikal in Siberia is the deepest.
Chilka lake of Orissa is largest lake in India.
Three main zones can be differentiated in a lake:-
• Peripheral zone (littoral zone) with shallow water.
• Open water beyond the littoral zone where water is quite deep.
• Bentic zone (bottom) or the floor of the lake
Microscopic floating organisms such as algae, diatoms, protozoans and larval forms are called plankton.
(ii) Marine ecosystem
Pertains to the seas and oceans including marine organisms
Distribution: Marine ecosystem covers nearly 71% of the earth’s surface with an
average depth of about 4000 m. Fresh water rivers eventually empty into ocean. Different kinds of organisms live at different depths of the sea or ocean.
Salinity of open sea is 3.6% and is quite constant
Flora and fauna: Biodiversity of the marine ecosystems is very high as compared to
terrestrial ecosystems. Almost every major group of animals occurs in the sea. Insects and vascular plant are completely absent in marine ecosystem. Maximum diversity of marine organisms is found in the tidal zone that is near the shore. Diatoms, algae, dinoflagellates and jelly fishes are some of the free floating life forms in oceans. Large crustaceans, molluscs, turtles and mammals like seals, porpoises, dolphins and whales are free swimming animals that can navigate. Bottom dwellers are generally sessile (fixed) organisms like sponges, corals, crabs and starfish.
terrestrial ecosystems. Almost every major group of animals occurs in the sea. Insects and vascular plant are completely absent in marine ecosystem. Maximum diversity of marine organisms is found in the tidal zone that is near the shore. Diatoms, algae, dinoflagellates and jelly fishes are some of the free floating life forms in oceans. Large crustaceans, molluscs, turtles and mammals like seals, porpoises, dolphins and whales are free swimming animals that can navigate. Bottom dwellers are generally sessile (fixed) organisms like sponges, corals, crabs and starfish.
India has a long coastline of about 8000 km (approx.) stretching along nine states and two island chains. At the coast a number of rivers form estuaries at their confluence with the sea.There are three gulfs - one on the east coast that is gulf of Mannar and two on the west coast i.e. gulf of Kutchch and gulf of Khambhat.
The tides are very important in determining the marine life. Nearly 14 species of sea
grasses and 120 species of sea weeds are found along the coast. Marine fisheries constitute a highly productive sector in India It is a source of food and employment to the coastal population.