Decoding the spatio-temporal dynamics within the benthic foraminiferal community structure from the northeast coastal...

Benthic foraminiferal assemblages are widely used as bioproxy for coastal environment monitoring. The present study investigated seasonal variation in benthic foraminiferal assemblages and their co-occurrence patterns in response to freshwater influx and nutrient dynamics along the northeast coast of the Bay of Bengal. Over a one-year period (2021-2022), benthic foraminiferal communities, sediment total organic carbon and dissolved nutrient concentrations in surface and porewater were analyzed from intertidal zones spanning Junput and Tajpur. The benthic foraminiferal abundance varied seasonally, with Junput showing increased abundance during the post-monsoon, followed by a decline in the pre-monsoon. In Tajpur, the benthic foraminiferal abundance decreased from post-monsoon 2021 to pre-monsoon 2021, then increased in monsoon 2021 samples. The benthic foraminiferal assemblages were dominated by Asterorotalia pulchella, Ammonia sp.1, and Ammonia sp.2. Notably, Asterorotalia pulchella showed a significant positive correlation with monsoonal rainfall and sediment total organic carbon, suggesting its potential as bioproxy for monsoon-influenced environments. Network analysis revealed the negative association between Asterorotalia pulchella and members of Ammonia spp., while Asterorotalia pulchella positively co-occurred with Trochammina inflata and Quinqueloculina seminula during the monsoon. Pearson correlation and multivariate analyses revealed that surface and porewater concentrations of dissolved nitrate and ammonia, along with precipitation, were key environmental variables associated with the spatio-temporal dynamics and co-occurrence patterns within the foraminiferal communities. These findings highlight the responses of benthic foraminifera to episodic nutrient enrichment and freshwater input and underscore their utility in ecological monitoring and paleoenvironmental reconstructions across tropical estuarine systems.