Effects of pollution on planktonic ciliates in Visakhapatnam harbour

Abstract

Observations on the physico-chemical and biological conditions at five selected stations along a decreasing gradation of organic pollution in Visakhapatnam harbour during 1989 revealed a preponderance of planktonic ciliates represented by as many as 25 species. Among these, Uronema marinum (16.9%), Holophrya nigricans (16%), Aspidisca lynceus (11.3%), Stylonychia mytilus (10.9%), Euplotes vannus (10.6%) and Stylonychia putrina (10.3%) constituted numerically the bulk (75.3%) of the population. At st.1 close to sewage outfall, where the waters are characterised by low dissolved oxygen ( median 0.98 mg. l(-1)), fluctuating salinity (12.7-31.1 x 10(-3)), low secchi-disc transparency(min. 14cm), relatively high temperature (max. 35 degrees C), Aspidisca lynceus (24.2%) was dominant. Downstream (st.V), where water quality improved relatively (transparency Im; temperature 26-31 degrees C), the principal inhabitant was Euplotes vannus (22.3%). During the study, it was possible to distinguish the ciliates into three different groups in relation to the prevailing water quality.