Indian J. Environ. & Ecoplan. 14 (1 -2): 101 - 108 ( 2007 ) PLANKTON DIVERSITY AT GOPNATH, GULF OF KHAMBHAT, GUJARAT Kauresh D. Vachhrajani and Pradeep C. Mankodi Department of Zoology, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodata - 390 002, India. . ABSTRACT Coastal planktonic diversity was studied at Gopnath, Bhavnagar district, located at juncture of Gulf of Khambhat and Arabian Sea. 28 phytoplankton and 25 zooplankton species were identified. Pinnularia, Biddulphia, Asterionella, Bacillaria and Aphanocapsa dominated phytoplankton. The zooplankton were dominated by Protozoan and Arthropod sp6cies. A few species of Cnidaria, Mollusca, Annelida and one Chaetognatha were also encountered. Overall density of phytoplankton was much less while among zooplankton Protozoan and Arthropod population exhibited some variation at different sampling sites that may be correlated to physical, physico-chemical characters and prey-predator relationships. Planktonic diversity with details of characteristic features of the area is discussed. Keywords: Plankton, Bacil/atiophyta, Cyanophyta, Protozoa, Arthropods. INTRODUCTION Gopnath, in Bhavnagar district, is located at the juncture of Gulf of Khambhat and Arabian Sea. This area is least influenced by anthropogenic activities. However, it is suspected that it might be influenced by activities alongthe gulf that is continuously enriched by pollutants through various rivers and effluent channels (Nanda, 2001; Sharma, 1995). At present there is no data available on the biota of this region of gulf. Therefore, present studies were carried out during 2003-2004 to generate a base-line data, which may be utilized in future for ecological and ecotoxicological studies. MATERIALS AND METHODS Study area: The coastal belt studied stretches over nine villages. The land takes a sharp curvature towards west and, western and eastern shores are divided by a long rocky strip which distinguishes the characteristic of these regions. Sampling site: The sampling sites were around 1.5 and 3 nautical miles (nm) away from the coast. Seven transects perpendicular to the shore were defined. On each of the transect sampling sites were located at around 1.5 to 3 nm distance. 101