Effect of industrial effluents on biota: A case study off Mangalore, west coast of India

Abstract

The inshore waters off Mangalore, receiving industrial effluent discharge were studied for phytoplankton, zooplankton and benthic populations, from December 1984 to May 1985. Total phytoplankton population varied from 7 to 1195 x 10³ cells.l^-1. Diatoms dominated the phytoplankton population. A striking feature observed was the persistent occurrence of certain species throughout the period of study. Zooplankton biomass ranged between 0.004 and 0.38 ml.^-3. Variations between months and depth contours were observed. Copepods, decapod larvae, chaetognaths and fish eggs and larvae occurred consistently. Copepod was the numerically dominant group but was outnumbered by decapod larvae at certain occasions. Sporadic occurrence of ctenophores, siphonophores, ostracods and cladocerans significantly contributed to the biomass. Macrobenthic fauna were largely composed of Polychaeta (48.8%) followed by Bivalvia (13.6%). Rich faunal composition and biomass were recorded at 5 m depth contour which decreased as the depth increased. Sandy substrata were inhabited by filter feeders whereas muddy substrata were rich in deposit feeders. The results indicated that except for some changes in phytoplankton population, the industrial effluent discharge has not caused any noticeable damage to the inshore areas off Mangalore.