Effect of pollution on the distribution of chaetognaths in the nearshore waters of Bombay

Abstract

Chaetognath fauna inhabiting the polluted waters was compared with that of clean waters for evaluating the impact of pollution. Regular observations at 11 locations off Bombay coast indicated a steady decline in chaetognath population in areas polluted with sewage. Incidence of chaetognaths at sewage polluted areas was limited mostly to periods of high tide; with population density much less (max 10.m super(-3)) than that of areas free of pollution (max 40.m super(-3)). Sagitta bedoti was the only tolerant species in sewage polluted areas. Areas polluted with industrial effluent showed better water quality and chaetognaths maintained steady and comparable population density (14-17.m super(-3)). Sagitta bedoti dominated the area from June to December while S.oceania became abundant from January to May. A decrease in the intensity of pollution was associated with an increase in the population density of Sagitta enflata and S.pulchra. Krohnitta pacifica, S.bombayensis and S.robusta were restricted to areas free of pollution.