Short essay on Aquatic Ecosystem

Water is an essential and most abundant substance in protoplasm. The life originated from water. Hence water is “Mother of all living world.” The water appears in many forms.

Pond Ecosystem

A pond as a whole serves a good example of a fresh water ecosystem. There is large number of natural and artificial ponds in India. Trees, shrubs and herbs surround a natural soil bordering the pond is wet and often inhibited by mesophytic or amphibious herbs.

Four constituent parts may be recognized in this ecosystem:

(a) Abiotic (or Non-living substances) components:

These include factors like light, temperature, pressure, soil, water, C0₂, pH, chemical, chemical compounds etc.

(b) Biotic (Living substances) components: 1. Producers: These are of two types:

(a) Micro-vegetation:

The micro-vegetation consists mainly of plankton. These are called phytoplankton. These are the algae, e.g., spirogyra, diatoms and oscillatoria.

(b) Macro-vegetation:

These consist of the following:

(i) Submerged vegetation:

This includes plants, which remain submerged in water, e.g., Hydrilla, Utricularia, Vallisneria etc.

(ii) Floating vegetation:

This includes plants, which float freely on the surface of water, e.g., Pistia, Nymphea, Eichhornia etc.

(iii) Emergent vegetation:

This includes rooted but emergent plants in the pond, e.g., Sagittaria, Ranunculus etc.

In the presence of sunlight, these producers synthesize complex pragmatic food materials using the carbon taken from the environment (water).

2. Consumers

These are heterotrophs, which depend for their nutrition on the organic food manufactured by producers, the green plants. Most of the consumers are herbivores, a few as insects and some large fish are carnivores feeding on herbivores. Some fish also feed on other carnivores as well. The consumers in a pond are distinguished as follows:

a) Primary consumers:

b) In the pond there are small consumers which feed upon the algae and green flagellates. They are heterotrophs and herbivores. These consumers include small crustaceans, fish, larvae etc.

c) Secondary consumers:

d) There are also consumers in the pond, which are carnivores and feed on small herbivores animals. These include small fishes, which are second) consumers.

e) Tertiary consumers:

f) There are also the predatory animals, which feed upon secondary consumers. These predatory large consumers include animals like large fishes, which are carnivores. These are tertiary consumers.

3. Decomposers

The autotrophs and heterotrophs in course of time die in the pond. The complex compounds of the dead protoplasm are decomposed by decomposers, which are mainly bacteria and fund As a result of this sort of decomposition, the complex substances are converted into abiotic substances, which can be used by the producers. Thus, the decomposers complete th| cycle in the ecosystem.

Lake Ecosystem :

Lakes are also stagnant water bodies. Lakes are described as good example for lentic environment. There are three zones:

(a) Littoral zone

(b) Limnetic zone

(c) Profundal zone

A lake has the same ecosystem like the pond although there are some differences between them:

(i) In lakes, the limnetic zone is the chief producing region whereas in ponds such region is the littoral zone.

(ii) The lakes differ from the ponds in being large bodies of water and being very deep so| that their bottom always remains dark.

(iii) Ponds have relatively small volume leading for rapid fluctuations of temperature, CO and pH.

(iv) Algal compositions are different in the two habitats; Ponds tend to have epipelic and epiphytic flora, which develop, over the whole area. Only occasionally, there is an epipelic flora. In lakes the epiphyte, epilithic and epipelic communities are developed as’ a girdle around the periphery leaving the centre free for plankton.