Importance of benthic-pelagic coupling in food-web interactions of Kakinada Bay, India

Abstract

Benthic components occupy the sediment layer of aquatic ecosystems and play a definitive role in overall system functioning and maintenance. The exchange of inorganic and organic materials between the sediment and water column through benthic-pelagic coupling plays a very important role especially in shallow water ecosystems. It is facilitated mainly by trophic interactions between the benthic and pelagic food webs, or specifically, between the coupling links i.e. the nodes that participate in coupling. Aquatic ecosystem models incorporating benthic food web in details have been few. In the present study, a food web model incorporating both benthic and pelagic food webs has been developed using EcoPath with EcoSim software, for Kakinada Bay ecosystem of Coastal Andhra Pradesh, India and has been analysed to get an idea about this system's functioning and integrity. Hypothetical perturbation scenarios (perturbation of biomass of two important benthic components – microphytobenthos and suspension feeding invertebrates) were applied to the model to study the effects of these two components on overall system robustness and integrity. The analysis of the base model revealed that while the bay system has not yet attained maturity, it also does not face much stress. While the system saw a decline in maturity with increase in microphytobenthos (MPB) biomass, increase in biomass of suspension feeding invertebrate (SFI) resulted in the exact opposite. Study of SFI biomass perturbation scenario also highlighted its role in coupling. Modelling studies incorporating benthic components as separate groups have been few. This work aims to provide a better insight into how benthic components may affect the whole system. Information regarding system health and resilience provided by such models can also be used as guidelines for fishery management and policy making.