Planktonic flagellates in relation to pollution in Visakhapatnam harbour, east coast of India

One year study (1994-'95) on planktonic flagellates at four selected statio ns along a decreasing gradient of pollution in the North Arm of Visakhapatn am harbour revealed as many as 17 species. Dinematomonas littorale, Dunalie lla sp., Spumella sp.. and Chromulina sp. were predominant. At St. I close to sewage outfall, where the waters are characterised by poor transparency (mean 0.75 m), fluctuating salinity (5.21-33.4 parts per thousand), low dis solved oxygen (0.0-5.53 mg/l) and relatively high temperature (max. 35.4 de greesC), Dunaliella sp. (40 %) was dominant. Downstream (st. IV) with impro ved water quality (transparency 2.59 m; stable salinity 27.7 parts per thou sand; dissolved oxygen, 3.72 mg/l), Dinematomonas littorale (43.3 %) was th e principal inhabitant. Overall, there was considerable heterogeneity in sp ecies composition and relative abundance of flagellates attributable to dif ferences in the prevailing water quality. Based on Principal Component Anal ysis (PCA), it was possible to distinguish the flagellate populations into two distinct assemblages. Of these, Spumella-Peridinium assemblage was char acteristic of polluted conditions at the outfall (st. I), and the Chromulin a - Sphenomonas assemblage was noticed at st.IV with improved water quality .