Does mining pollution affect foraminiferal distribution in Mandovi estuary, Goa India

Abstract

A total of 10 surface sediment samples were collected in the premonsoon season in 1990 from the Mandovi estuary, Goa. Study revealed presence of 14 species of foraminifera. The foraminiferal data is of special significance because the same can be compared with foraminiferal data of RAO (1974) based on the samples collected in 1972 from the same area. The study reveals that during 18 years total foraminiferal number (TFN) came down considerably (2 to 42 specimens/gm in 1990 as compared to 10 to 139 specimens/gm in 1972). Similarly, total species number (TSN) also declined from 18 (in 1972) to 14 (in 1990). It is postulated that decline in fauna is due to continuously increasing suspended load (2-4 mg/l in 1972, 4.5-8 mg /l in 1982 and 6.69-114.49 mg/l in 1990) in the estuary. This increased suspended load can be attributed to mining activities in the catchment area of Mandovi River along with its tributaries. Extraction of one tonne of iron ore generate about 1.5 to 4 tonnes of mining reject, and over the years more than 1 billion metric tonnes of mining reject is estimated to have accumulated in mining belt of Goa. The loose mining reject gets eroded due to flooding during monsoon and transported downstream, thus increasing suspended load in river. In view of the foregoing it is surmised that decrease in foraminiferal population in Mandovi estuarine sediments during 1972-1990 indicates influence of mining pollution.