Distributional pattern of benthic foraminiferal morpho-groups in the shelf region off Mangalore : Environmental implications

Abstract

The foraminiferal population in 45 surface sediment samples (20-86 m water depth) off Mangalore, was divided into benthic and planktonic assemblages. Within the benthic community based on the external test morphology, the population was further placed into two broad morpho-groups namely, angular-asymmetrical and rounded-symmetrical. The surficial distribution of these groups revealed that angular-asymmetrical forms are abundant in relatively deeper region whereas rounded-symmetrical forms flourish in nearshore regions. Such distinct distribution may be ascribed due to river borne turbulence. It further suggests that rounded-symmetrical forms favour high turbulence associated with increased fresh water river discharge in shallow regions. However, since fresh water river discharge is linked with precipitation over the catchment area, the results may show high potential in generating proxy data for the reconstruction of paleomonsoonal history through the study of morpho-groups in subsurface sediments of coastal regions, An anomaly in the distribution pattern is noticed off New Mangalore Port which is attributed to dredging for the navigational channel.