Biotic Communities Of Freshwater, Autogenic and Allogenic Process

Biotic Communities of Freshwater

There are two types of freshwater bodies such as Lentic (stagnant) water bodies and lotic (running) water bodies, species, distribution in these different water bodies are different which is given below.

1: Lentic bodies:

In the lentic bodies, there are three vertical zones which are littoral, limnetic and profundal zone.

A: Littoral zone:

In the littoral zone, there is the presence of the producer and the consumers.

Producers: In the littoral zone, the producers are mainly rooted or benthic plants mainly seed plants belonging to the division spermatophyte and the floating green plants, the phytoplanktons which are mainly the algae, some species of spirogyra, Oedogonium are also found in the littoral zone which is attached or associated with the rooted plants.

From shallow to deeper water zones in lakes and ponds we find;

I: Zone of emergent species: This zone includes species of Typha, Scirpus, Saggitaria, Phragmites etc.

II: Zone of rooted plants with floating leaves: This zone includes species of Nymphaea, Nelumbo, Trapa, Monochoria etc.

III: Zone of submerged vegetation: This zone includes species of Myriophyllum, Elodea, Potamogeton, Vallisneria, Utricularia etc.

Consumers: All the five life habits of consumers are well represented in the littoral zone. The periphytic organism is pond snails, damselflies nymphs, dragonfly nymphs etc. The benthic organism is crayfish, Isopods, Mayfly nymphs etc.

The zooplanktons are the water fleas, some cyclopaedia, and many ostracods. An organism like whirligig beetles large water striders belongs to the neuston. Various adult empire is the nekton organisms. Also, the amphibians such as frogs, turtle, and the water snakes are exclusively found in this zone.

B: Limnetic zone

Producers: The phytoplanktonic algae which are found in the littoral zone are also found in the limnetic zone. Besides, there are algae like green flagellates chiefly the dinoflagellates species of euglenids and Volvo cnidae.

Consumers: The zooplanktons represent a few species but are large in number. Copepods, cladocerans, and the rotifers are chiefly present in this zone. Swimming animals are fishes as gizzard shads.

C: Profundal zone

This zone has the two types of the species diversity because of the no effective light penetration. Major life forms are bacteria and the fungi, blood worms, annelids, small cans of family spheroidal and phantom larvae.

Lotic communities

There are two zones which are present in the lotic communities. They are rapid and pool zone. They are present with the different species distribution.

Rapid zone;

Organism showing adaptations for the maintaining positions and to withstand the pounding of the swift rapids and the waterfalls. Mainly constituents benthic and the periphytic organism.

Procedure: The plants are being attached with the green algae such as the Cladophora, encrusting and the aquatic mosses of the genus Fontinalis.

Consumers: These consists of the freshwater sponges which content their cases to the stones. The presence of the hooks and the suckers in the caddis fly larvae stimulus and the blepharocerid larvae enable them to withstand the pounding of the swift rapids and the waterfalls. These strong swimmers such as darters fish are also found in the rapid zone as consumers.

Pool zone:

The slowly moving deeper water is more favourable for the Nekton, Neuston, and the Planktons. Pool communities may be expected to contain some organism which also occurs in the littoral zone in the ponds. For example, the blue gill fish i.e typical pond fish also resides in the deeper pool of the stream. Stream nekton and the burrowing forms as calms, burrowing odonatan and the Ephemeroptera are the more abundant In the pool.

Major changes found in the lentic environment when allogenic processes exceed the autogenic processes

Autogenic process in the fresh water i.e in the lentic ecosystem are those which are due to the biotic processes within the system and the allogenic processes are those which are due to the geochemical process acting from without. There is the influence of the both allogenic and the autogenic factors in the lentic environment and both factors are responsible for its regulation. But the autogenic processes tend to stabilize or slow down the processes of alteration of the lentic ecosystem and the allogenic processes not only stabilize the lentic ecosystem. But the ecosystem may extinct its processes is negligible than the autogenic processes.

The pronounced effects were seen in the lentic environment due to the increase in the allogenic processes is eutrophication of the lake whether natural or cultural. This result when the nutrient is imported into the lake from outside lake that is watershed. Such increased amount of nutrients increases the biological activity and thus sedimentation of the microorganism and other leads to a succession of the water body. This process of the filling up of lakes is also accelerated by the sediments carried from the watershed area due to allogenic factors.

The climatic conditions such as atmospheric humidity, temperature strength of the wind, precipitation etc. are also the allogenic factors which influence the lentic environment. But the influence of these factors are observed during different seasons only and their factors will be more or less in the equilibrium over a period of one year or more. The heavy precipitation during the rainy season, however, the important factor which causes siltation of lentic environment. The anthropogenic activities like speeding up of the geological processes, encroachment of boundaries of the lake areas and the pollution such as the chemical thermal etc. in and around the lakes are also being the cause of gradual collapse up of the autogenic processes and this the lentic ecosystems.

It is important to note that, autogenic succession is altered, if the allogenic processes exceed in the lentic environment and so the lentic ecosystem i.e prominently in transitory ones show the reversal trends of the autogenic succession by the influence of such geochemical forces. The autogenic processes include the role of biological community with large and the complex organic structure that mitigates perturbations of the physical environment. But the exceeding of the allogenic processes to the autogenic process robs the system of this protective mechanism and collapses the ecosystem.

References:

Miller, Jr. G.T. Living in the Environment. Wadsworth Publication, 2003.

S.C., Santee. Environmental Science. India, New Center: New Center Book Agency (P) Ltd, 2004.