Today, here in this article, we will address the characteristic features of aquatic ecosystems:
1) Fresh Water Ecosystems:
Fresh water ecosystems are characterized as lotic (having flowing water) or lentic (still water). Various types of fishes such as darters, trout, and salmon are found in mountain streams. Further downstream we also find warm water fish, such as carfish and carp.
Lentic bodies like pools, ponds, some swamps, bogs and lakes vary considerably in physical, chemical and biological characteristics. They are dominated by floating and emergent vegetation rooted in the bottom such as reeds and cattail, water lilies and some submerged but rooted species. Frogs, snakes, snails,clams and considerable variety of adult insects and their larvae are also found here.
2) Marine Ecosystem:
The most important physical characteristic that distinguishes marine ecosystems from freshwater ecosystems is the salinity of the water. The five major marine ecosystems are as under.
When freshwater meets seawater, and the salinity of seawater is diluted. The primary producers in estuaries include plankton, large attached aquatic vegetation, and emergent vegetation such as cord grass. Estuaries ecosystems are nursery grounds for many marine fishes, mollusks and crustaceans.
b) Intertidal Zones:
They extend from splash zone of ocean waves to the low tide marks. More motile animals such as fish and some crabs, move in and out of intertidal zones with the tides. Other animals such as amphipods, isopods, ghost crabs and numerous polychaetes, burrow beneath the sand and mud of the intertidal areas.
c) Neritic Ecosystems:
It consists of relatively shallow water that extends from the littoral zone to the edge of the continental shelves. They are dominated by attached algae and are important in contributing to primary production. Among animals include crabs, sponges, echinoderms, corals and polychaetes.
d) Oceanic Zones:
It extends from continental shelves into the relatively unproductive open ocean. Phytoplankton forms the base of the food web. Animals found at these great depths may have luminescent organs.
e) Coral reefs:
They are one the most highly productive ecosystem in the world. They are associations of stony coral and algae. The greatest depth at which they can grow is between 50 to 60m. Below this depth light is insufficient to support the growth of the zooxanthellae necessary for reef formation.