Decomposition and subsequent remineralization of mangrove detritus is important in nutrient dynamics within the forest as well as in offshore system. In order to study the impact of detritivorous fish on the mangrove estuarine detritus food web, a five compartment model of detritus food web dynamics has been developed for mangrove estuarine creeks of Hooghly- Matla Estuarine complex, Sundarban. The model simulates concentration of nutrient, biomass of phytoplankton, zooplankton, detritus and detritivorous fishes. Almost 70% of the detritus formed in the soil was being washed in the estuarine water to act as source or sink of nutrient for the primary producers of aquatic food chain. A significant amount of detritus in the estuarine water is readily consumed by a group of detritivorous fishes before it is being rematerialized completely in to inorganic nutrient form. The model has been calibrated and validated using field data accordingly. Increased detrital nitrogen values in the late monsoon and post monsoon months, assists the growth and high yield of detritivorous fishes as found in simulated and field observations. Comparison of simulated and observed results demonstrates the dependence of phytoplankton growth is a function of nutrient concentration and zooplankton grazing. Model results also show the dependence of detritivorous fishes on detritus which is a function of detritus biomass. In turn, detritus biomass is dependent upon several factors like mortality of phytoplankton, zooplankton, and detritivorous fishes; and chiefly on litter biomass and litter decomposition.
