Species Composition and Diversity of Plankton in the River Seeta at Seetanadi, the Western Ghats, India

Plankton is one of the most rapid detectors of environmental changes. In the present investigation plankton species composition and diversity was studied for a period of 14 months in the river Seeta from April 2005 to May 2006, the Western Ghats, India. A total of 4 phytoplankton divisions (Chlorophyta, Bacillariophyta, Rhodophyta, Cyanophyta) and 4 zooplankton phyla (Protozoa, Porifera, Nematoda, Arthropoda) were recorded during the study period. A total of 78 species of plankton belonging to 29 families have been documented. Of these, a total of 71 species of phytoplankton and 7 species of zooplankton were recorded. Among the 22 families of phytoplankton, Naviculaceae (13 spp.), Desmidaceae (13 spp.), Zygnemataceae (7 spp.) and Fragilaraceae (7 spp.) had the highest species representation followed by Cymbellaceae (4 spp.), Ulotrichaceae (3 spp.), and Hydrodictyaceae (3 spp.). A total of 6 and 9 families were represented by 2 and 1 species respectively. Among zooplankton, a total of 7 species belonging to 7 families were recognised. The phylum Protozoa was represented by 4 spp. followed by Porifera, Nematoda and Arthropoda with 1 species each. Diversity parameters such as species diversity (H' log) ranged from 1.2889 (August 2005) to 2.7056 (March 2006), whereas evenness (J') fluctuated between 0.7099 (May 2006) and 0.9163 (July 2005). The species numbers was lowest (5) during August 2005 and highest (27) in February 2006. The highest number of plankton was 1, 23,000 per liter and the lowest was 11,000 per liter during June 2005 and February 2006 respectively. The plankton diversity and environmental parameters have been subjected to multivariate statistics such as Principal Component Analysis (PCA) and Bray Curit's similarity matrix and results were discussed.