A.S. TEKADE, G.N. KULKARNI AND S.T. INDULKAR
Abstract
The present investigation assessed the influence of thermal effluent from the Jaigad coastal power plant, Ratnagiri, Maharashtra, on phytoplankton and associated zooplankton in the near-shore coastal waters. Monthly sampling was carried out from September 2014 to May 2015 using a motorized fishing boat. Five representative sampling stations (S1, S3, S5, S6 and S8) were considered for the present detailed analysis, covering the reference station and the offshore gradient. Surface and bottom water samples were collected during low tide. Phytoplankton and zooplankton were collected with a 60 ?m plankton net, preserved in 5% neutralized formalin and examined microscopically. Chlorophyll-a was estimated spectrophotometrically following extraction with 90% acetone. At S1, chlorophyll-a varied from 1.15 to 8.26 mg m-³ and phytoplankton abundance from 340 to 1855 nos. l-1. At S3, the corresponding ranges were 0.17-3.96 mg m-³ and 175-390 nos. l-1. At S5, S6 and S8, chlorophyll-a ranged from 1.32-6.25, 1.32-7.56 and 1.34-7.69 mg m-³, respectively. Phytoplankton abundance at these stations ranged from 915-1897, 590-1350 and 270-1120 nos. l-1, respectively. Diatoms formed the dominant phytoplankton group, with Coscinodiscus, Skeletonema, Navicula, Leptocylindricus, Fragilaria, Pleurosigma, Nitzschia, Ditylum and Chaetoceros among the principal recorded forms. Zooplankton was dominated by copepods, particularly calanoid forms. The reduction in chlorophyll-a and phytoplankton near the effluent influence zone followed by recovery toward offshore stations indicates that the effect of thermal discharge was localized. The overall planktonic condition of the coastal waters did not indicate a persistent adverse effect attributable to the thermal discharge.