* Department of Zoology, Govt. Arts College (Autonomous), Kumbakonam 612001 ** Department of Botany, Govt. Arts College (Autonomous), Kumbakonam 612001
Present investigation was carried out in the College Lake situated in the College Campus of Government Arts College (Autonomous), Kumbakonam, Thanjavur District, Tamil Nadu (between 10 º 57' and 26º 17' of the north latitude and 79º 22' and 51º 84' of the East longitude) to understand the biodiversity of the Lake
3. RESULTS AND DISCUSSION The major biological communities occupied in the experimental are phytoplankton. Most of the phytoplankton p is not harmful and are vital as primary producers and which also supports aquatic fauna especially zooplankton [17]. In total 26 phytoplankton species were recorded in all the four study sites of the experimental lake (Table 1)
S. No Table 1 Phytoplankton in different sites of College Lake Name of the species Site I Site II Site III Site IV 1 Ankistrodesmus convolutus Corda + + - + 2 Chlamydomonas simplex + - + - 3 Chlorella vulgaris Beijerinck + + - + 4 Closterium acerosum Ehr. - + + - 5 Cl. acutum Breb. + - - + 6 Cl.dianae Ehr. + - + + 7 Cl. lanceolatum Kutz. + + - - 8 Comarium granatum Breb. - + + - 9 Staurastrum pinnatum Turn. + + + + 10 Selenastrum gracile Reinch + - - + 11 Scenedesmus acuminatus - + + - 12 Pediastrum duplex Meyem. + + - - 13 Phacus orbicularis Huebnear + - + +
14 Trachelomonas sp. + + + - 15 Euglena acus - + + + 16 Amphora gigantea Cl. - + + + 17 Cyclotella sp + + - - 18 Cymbella affinis Kutz. + + + + 19 Fragilaria intermedia Grun - + + - 20 Melosira sp. + - + + 21 Nitzschia bilobata Grun. - + - + 22 Anabena sp. + - + + 23 Anabaena oryzae Fritsch + + + - 24 Oscillatoria sp. Vaucher - + - + 25 O.chalybea ( Mertens ) Gom. + - + - 26 O. limosa Ag. ex Gom. - + - +
Among the Chlorophyceae species, Staurastrum pinnatum Turn recorded in all the four study sites and the species like Ankistrodesmus convolutus Corda; Chlorella vulgaris Beijerinck i and Closterium dianae Ehr were dominated in three sites and the other species recorded only two sites
3.1 Zooplankton Diversity Zooplanktons are the ecological indicators of the water bodies, and their distribution and abundance is an index for the health of an aquatic environment [20 & 21]. Comparatively low zooplankton species were recorded (only 8 species). Zooplankton of lake waters are dominated by Protozoans, Rotifers, Ostracods and the sub-classes of the crustaceae, the Cladocerans and the Copepods (Table 2)
Table 2 Zooplankton recorded in different sites of College Lake S. No Name of the species Site I Site II Site III Site IV 1 Daphnia Catawba + - - + 2 Bosmina longirostris - + + + 3 Cypris larva + - + - 4 Lecane + + - + 5 Monostyla - + + - 6 Asplanchna + - + + 7 Cyclops + - + + 8 Eucyclops agilis - + - +
Phytoplankton and zooplankton species concentrations were showed significant negatively correlated almost in all the four study sites of the experimental ponds. More over the Cyclopoids has greater importance mainly because Microcyclops, Megacyclops and Mesocyclops attacks mosquito larvae and helps in biological control
3.2 Insect population In the experimental Lake during present investigation insect population was dominated d by four important species (Table 3). As par as the density is concerned Chloroperia sp was dominated entire period of investigation
Table 3 Water insects recorded in the experimental lake S. Name of the Site Site Site Site No species I II III IV 1 May flynymph - + - + 2 Chloroperia + + + + 3 Rhithrogena + - + + 4 Whirlgig beetle + + - +
3.3 Hydrophytes y Macrophytes comprising of emergent, free-floating and submerged forms are remarkable plant life forming a more or less precarious footing in the lake ecosystem. Macrophytic vegetation of the lake recorded six species recorded in littoral zone (Table 4) and four species in emergent zone (Table 5) of the lake.
Table 4 Macrophytic plant species identified in the experimental lake S. Name of the species Site I Site Site Site No II III IV 1 Nymphaea sp. + + - + 2 Aponogeton sp. - - + - 3 Potamogeton sp. + - - + 4 Hydrilla sp. - + + + 5 Vallisneria sp + + + - 6 Potamogeton sp. + + + +
Table 5 List of macrophytic species in the emergent zone S. No Name of the species Site I Site II Site III Site IV 1 Cyperus sp. + + - + 2 Typha sp. - + + - 3 Sagitaria sp. + + + + 4 Marsilea sp. + + - +
Among the littoral submerged and floating species Nymphaea sp., Hydrilla sp. Vallisneria sp. Potamogeton sp were dominating in all the four study sites whereas the other two species like Aponogeton sp and Potamogeton sp were recorded ddonly in two study sites
4. CONCLUSIONS Revealed the past limnological studies of the experimental lake clearly give the same trend that have been observed during the present investigation. Moreover, the increased level of pollution indicating species establishment in the lake clearly indicated the level of pollution. Nevertheless, the restoration of the lake can be possible by adapting few simple ways like de-silting during summer dry periods and the avoiding the water inflow to the lake from Cavery River which had already been polluted