Dynamic simulation and steady-state analysis of a bentho-pelagic coupled ecosystem under different simulation scenarios

Trophic dynamic studies of aquatic ecosystem are usually based on either dynamic or state-state models of energy and material transfer, comprising of a few functional tropic levels such as phytoplankton, primary consumers and secondary consumers. However, though benthic components (and production) are important parts of an aquatic ecosystem, they are often omitted from such approaches.Considering this inadequacy of previous simulation approaches, the aim of the present study, is to investigate the effect of benthic components on overall system dynamics. The objectives of this study are (a) to develop and study a dynamic model for Kakinada bay to understand how benthic components interact with others under a fixed set of conditions, and to find the sensitive parameters for such a benthic-pelagic coupled system (b) to study the effects of different biomasses of benthic components via scenario analysis and (c) to identify the different equilibrium states that a benthic-pelagic coupled system such as Kakinada Bay may reach.On running the simulation for a period of 5000 days (∼10+ years), the system was not seen to reach any equilibrium state; however, all state variables considered in the model were seen to coexist even at the end of this period. While zooplankton was found to be the most sensitive state variable, parameters directly associated with benthic components were indicated to be the most sensitive. Microphytobenthos was negatively correlated with phytoplankton which was corroborated by results of the perturbation scenario analyses as well. Only one equilibrium state – microphytobenthos dominated steady state was found for Kakinada Bay system when certain parameters were slightly changed.