Bhandarkar, S.V. and Paliwal, G.T.
The present study is primarily based on the work conducted on the cultural eutrophication in lentic ecosystem of Dhukeshwari temple pond situated at Deori. The Dhukeshwari temple pond is under unsustainable anthropogenic stress. The zooplankton assemblages were recorded qualitatively and quantitatively. Zooplanktons was represented by 83 species, and consisted of members from Rotifera (46) belonging to 15 families from 03 orders; Cladocera (27) belonging to 06 families; Copepoda (6) and Ostracoda (04). The zooplankton consisted of Rotifera, Cladocera, Copepoda and Ostracoda. The quantitative relationship amongst different groups of zooplankton in Dhukeshwari Temple pond was Rotifera > Cladocera > Copepoda > Ostracoda during the study. In Total zooplanktons the Rotifera were recorded maximum (2039/ltr) (61%) followed by Cladocera (1033/ltr) (31%), Copepoda (202/ltr) (6%), Ostracoda (84/ltr) (2%). It is disclosed that the rotifer fauna can be linked with favorable conditions and availability of abundant food in the form of bacteria, micro-phytoplankton, nano-plankton, animal waste and suspended detritus in the pond water. The Crustacean assemblage forms the major part of zooplankton community constituted by the crucial group like Cladocera, Copepoda and Ostracoda and the diversity within groups. They are sensitive to environmental accelerations, therefore these organisms used as important tool to evaluate the trophic status of ecosystems. In the present study, 27 species of order Cladocera were recorded from the 06 families, with highest diversity with 08 species in family Chydoridae and family Aloniae with 08 species.
Keywords: Zooplankton | Rotifers | Crustacea | Trophic status | Ecosystem
Introduction
Freshwater ecology is an intriguing field because of the great diversity of aquatic habitats. The freshwater habitat exhibit huge diversity based on the genesis, geographical location, hydro-biological regimes and substrate factors. The ponds and lakes are more productive ecosystems and their importance as life supporting systems in controlling water cycles and cleaning the environment has acknowledged by wetland experts worldwide. Generally lake possessed a vast array of diversity in its faunal composition which is dynamic and responsive to deviation from normal ecological homeostasis. Unfortunately, they are degrading, become polluted due to inflow of domestic effluents, washing clothes, vehicles, cattle, immersion of idols etc. resulting in the accumulation of toxic chemicals and sludge leading to ecological imbalance. A well established and balanced ecosystem has all the physicochemical factors in optimum range and support maximum diversity of biota. However due to open nature of the system, continues exchange of matter and energy goes on. Any change in the physicochemical environment has got its effect on biotic community due to fact that different species of flora and fauna show variations in their responses to the altered water quality. Hence, highly sensitive species are eliminated altogether while other, more resistant and tolerant dominate the medium.
The ‘Trophic status’ of any water bodies can evaluated by physicochemical and biological characteristics and also be determined by physiographical parameters. The freshwater bodies can be classified with respect to their biological productivity. Rawson (1956), Zafar (1959), Pennak (1955), Neumann (1927), Strom (1924), Rao (1953), Zafar (1964), Welch (1952) gave major contribution for the classification of water bodies. It is a process useful to characterize the ‘Trophic Status’ of a particular water body at any given time. A term ‘Trophic status’ of water body is used as a description of the water body for this purpose. The status of freshwater ecosystems can be categorized on the basis of richness of nutrients. The poor nutrient material, low productivity and when the water is clear, known as Oligotrophic state which having low concentration of plant life. Only small quantity of organic matter grows in an Oligotrophic lake or ponds; phytoplankton, zooplankton, attached algae, macrophytes (aquatic weeds), bacteria and fish are all present as small populations. There may be various kinds of plankton and other organisms but not very many of each species or type. With little the production of organic matter little accumulation of organic sediment at the bottom and therefore smaller the population of bacteria and due to very little consumption of oxygen, lots of oxygen present from surface to bottom. In Mesotrophic state, intermediate level of nutrients; production of plankton is intermediate, some loss of oxygen in lower waters, oxygen may not be entirely depleted and water is moderately clear with Secchi disc depths. Mesotrophic ecosystems usually have dispersed weed beds and weeds are sparse within bed. Fish is often good in such waters. While in Eutrophic state, higher the nutrients therefore the productivity is high and lower water clarity, resulting in good plant growth and possible algal blooms (Closs et al., 2004). Such waters also produce high number of zooplankton and the fish that feed on the zooplankton. Due to higher the production of organic matter provides the food for high numbers of bacteria and benthic macro-invertebrates. Eutrophic waters are often relatively shallow. Although the intensity, frequency and extent of algal blooms have tended to increase in response to human-induced eutrophication, algal blooms are a naturally occurring phenomenon. The rise and fall of algae populations, as with the population of other living things, is a feature of a healthy ecosystem (Bianchi et al. 2000).
The Importance of plankton communities, in the Trophic dynamics of freshwater ecosystems has long been recognized, as these organisms, not only regulate the aquatic productivity by occupying almost middle position in food chain, but also indicate environmental status in a given time. These organisms are regarded as valuable bio-indicator to depict the Trophic status of water quality of their environments within limnosaprobity (Sladecek, 1983). In India biological assessment was effectively employed as an indicator technique in a number of recent studies involving assessment of pollution impact from domestic sewage and industrial effluents (Deevey et al., 1941; Koul et al., 2000). Historically Butcher (1924) was the first to recognize the importance of biological analysis in overall assessment of aquatic environment.