Water Physico-chemical Characteristics, Species Diversity and Density of Zooplankton in Two Perennial Lakes of Coimbatore City (India)

In order to assess the suitability of the Ukkadam lake (Lat. 10.99° N and Long. 76.96° E) and the Singanallur lake (Lat. 10.59° N and Long. 77.88° E) of Coimbatore (Tamil Nadu, India) for inland aquaculture, the species diversity and density of zooplankton were assessed for a period of one year (December, 2015 to November, 2016) under four seasons, post-monsoon, summer, pre-monsoon and monsoon. In the Ukkadam lake, a total of 28 zooplankton species, including 7 species of Rotifera, 6 species of Cladocera, 8 species of Copepoda and 7 species of Ostracoda were identified. Their mean density were 4890 ind. l-1 for Rotifera, 5338 ind. l-1 for Cladocera, 5811 ind. l-1 for Copepoda and 8002 ind. l-1 for Ostracoda (total of 24042), and their order of dominance were Ostracoda > Copepoda > Cladocera > Rotifera. In the Singanallur lake, a total of 24 zooplankton species, of which 7 species of Rotifera, 6 species of Cladocera, 6 species of Copepoda and 5 species of Ostracoda were identified with the mean density of 3146 ind. l-1 for Rotifera, 2492 ind. l-1 for Cladocera, 2342 ind. l-1 for Copepod and 2355 ind. l-1 for Ostracoda (total of 10337) in the following order of dominance: Rotifera > Cladocera > Ostracoda > Copepoda. This study revealed that the annual zooplankton abundance was found to be higher in the Ukkadam lake than that of the Singanallur lake (24042 ind. l-1 and 10337 ind. l-1, respectively). When looking seasonal variation both the Ukkadam and the Singanallur lakes showed maximum zooplankton abundance during summer season (25989 ind. l-1 and 10821 ind. l-1, respectively), followed by post-monsoon (24089 ind. l-1 and 9577 ind. l-1, respectively), pre-monsoon (23954 and 10807 in, respectively) and monsoon (20436 ind. l-1 and 10142 ind. l-1, respectively). In both lakes, zooplankton was positively correlated with physico-chemical parameters, such as water temperature, pH, salinity and electrical conductivity, and not properly correlated with dissolved oxygen and total dissolved solids. Regarding the diversity indices, considerable degree of differences were seen between these two lakes, the Ukkadam lake showed more diversity and density than those found in the Singanallur lake. When individual lake was considered, considerable degree of differences was seen in the species diversity of each zooplankton group in different season.