BIO-08 Tracking anthropogenic changes using benthic fauna
Mapping the Changes in Coastal Biotopes of Bay of Bengal- Applicability of Benthic Foraminifera Coenosis as Bioproxy
Arkaprava Mandal* , Integrative Taxonomy and Microbial Ecology Research Group, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, India
Punyasloke Bhadury, Integrative Taxonomy and Microbial Ecology Research Group, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, India

Coastal oceans are home to rich biodiversity and offer multifarious ecosystem services, including food, livelihood, protection of coastal shorelines, and sustaining the blue economy. The northeast coastal Bay of Bengal lies along the Ganga-Brahmaputra-Meghna delta and forms several microhabitats driven by seasonal precipitation, freshwater flow from perennial and seasonal rivers, saline water inflow, and anthropogenic disturbances. The site Junput of coastal Bay of Bengal has moderate variations in environmental conditions with limited anthropogenic activities, including manual fishing and occasional eco-tourism. To assess the scale of disturbances witnessed by the coastal Bay of Bengal, benthic foraminiferal diversity was studied over seasons, further reinstated by the seasonal variations in dissolved nutrient conditions in the coastal Bay of Bengal. Benthic foraminifera can also potentially be used as a bioproxy for assessing ecosystem level degradation resulting from anthropogenic stress in tropical coastal oceans. Abundances of benthic foraminifera range between 10-150 individuals/10 cc of wet sediment over the studied period. Extensive sampling of the intertidal study points representing discrete hydrodynamic gradient highlighted the overwhelming abundance of calcareous taxa were calcareous taxa Asterorotalia trispinosa, Ammonia spp., Quinqueloculina spp., and agglutinated taxa Trochammina inflata. Agglutinated taxa were low in abundance and less frequent across study site indicating the deteriorating ecological health of the coastal Bay of Bengal and the potential influence of saline and freshwater mixing. The values of inorganic nitrogen (nitrate and ammonia), ortho-phosphate, and silicate exhibited wide variation, indicating the strong influence of anthropogenic forcings in recent years. The higher number of degraded tests through out studied period highlighted taphonomic alteration in the study area and indicated the sediment was more likely to be anoxic. Anaerobic degradation of organic matter within the sediment leads to hydrogen sulfide production ammonia, and its upward migration can result in taphonomic alteration of the test. Overall, this study has provided critical insights into possible ecosystem level changes in the northeast coastal Bay of Bengal.