Benthic foraminiferal sedimentation in the northeast coastal Bay of Bengal using a custom designed sediment trap

The dynamics of sediment and biogenic materials are key to understanding fluxes within shallow coastal ecosystems. However, capturing these processes are particularly difficult in high-energy intertidal environments, where strong tidal currents, wave resuspension, and freshwater flow frequently disturb sediment traps. In this study, a novel and low-cost sediment trap (~ $20 USD per unit) has been designed, optimized, and implemented for shallow, high-energy coastal settings, with the ability to capture resuspended particles primarily influenced by tidal currents and wave action. In total, 18 sediment traps were placed along the intertidal zone of the northeast Bay of Bengal, influenced by freshwater, for a period of 60 days. Only three traps were successfully retrieved due to challenging hydrodynamic conditions. Despite limited recovery, the traps effectively captured short-term sedimentation and biogenic flux signals. The total number of foraminifera recovered in sediment traps varied from 80 to 110 tests/10 cc. In total, eight taxa representing five families of foraminifera were identified. Rose Bengal staining confirmed that these benthic foraminifera were dead at the time of deposition, indicating post-mortem resuspension and transport within the nearshore coastal environment. The occurrence of Ammonia spp., Quinqueloculina spp., and Bolivina sp. suggests sediment reworking and transport within the nearshore coastal environment, but contributions from potential source areas could not be distinguished. The co-occurrence of planktonic Globigerinoides sp. suggests that these tests were resuspended from sediments before being transported coastward. These preliminary observations suggest that lateral transport and wave-driven resuspension influence the deposition of benthic foraminiferal tests within the study area. Notably, the study demonstrates the feasibility of using a low-cost custom-designed sediment trap to investigate short-term sedimentation processes in high-energy intertidal environments. Future applications will require further improvements in trap design and stabilization.