Effect of ecosystem stressors on biogeochemical processes and bivalve-mediated bioremediation approaches for estuary resilience

Nutrient loading, derived from human-induced land-based activities, poses a significant risk of anthropogenic eutrophication in most estuaries worldwide and is considered a high-priority ecosystem stressor. Similarly, estuaries in the southern Gulf of Saint-Lawrence, Canada, are facing threats from this ecosystem stressor leading to potential nutrient over-enrichment, which not only affect primary production timing and abundance but can also alter the entire ecosystem dynamics. Determining the trophic condition of such estuaries becomes more critical when 58 % of the system is covered with natural populations of bivalve species. Therefore, we developed for the first time, a high-resolution 3-D coupled physical-biogeochemical model for the Bouctouche Estuary, Canada, based on Finite Volume Coastal Ocean Model and Integrated Compartment Model (FVCOM-ICM) whose water quality kinetics are further integrated with a benthic filter-feeder Dynamic Energy Budget (DEB) ecophysiological submodule to examine the present physical-biogeochemical condition, predict the responses of pelagic-benthic activity to different stages of nutrient loading and promote bivalve-mediated bioremediation approach. Results revealed that nutrient loading areas are characterized by low dissolved oxygen and biogeochemically distinct waters. Further, heterogeneity in estuarine biogeochemical processes is responding to water renewal time. Concomitantly, bivalves can bioextract about 11 % of riverine nitrogen inputs seasonally showing that both components can affect the net primary production distribution. Overall, this modeling framework will allow an ecosystem-based bioremediation approach for effective nutrient management to enhance estuary resilience.