Distribution patterns of Recent planktonic foraminifera in surface sediments of the western continental margin of India

Abstract

Study of Recent plankton foraminifera from the surface sediment samples of western continental margin of India reveals the ecological preferences of the different planktonic foraminifera species in the area. Higher absolute abundance of planktonic foraminifera in the offshore associated with the lower frequences of the productivity indicator Globigerinoides bulloides and lower absolute abundance in the nearshore with higher frequences of G. bulloides appears to suggest that productivity does not control the absolute abundance of planktonic foraminifera in the area.In general the difference in absolute abundance between offshore and nearshore indicates that the dilution by terrigenous and other biogenic (benthic foraminifera and diatoms) material governs the absolute abundance of planktonic foraminifera. G. sacculifer shows a significant positive correlation with salinity and a negative correlation with temperature, which reflects its preference for higher salinity and lower tempertue of the surface water. G. ruber abundances are related to a distinct highly saline Persion Gulf water mass in the eastern Arabian Sea. Beogloboquadrina dutertrei shows a strong inverse relationship with surface water salinity in the eastern Arabian Sea. Therefore, the relative abundance variations which varies according to the strength of the northern monsoon. The high diversity of planktonic foraminifera in the offshore is attributable to equitable environmental conditions. The high-salinity surface waters (> 36 degrees 00) and terrigenous dilution in the northeastern Arabian Sea limit the diversification of species in this region