Numerical modelling of the benthic-pelagic coupling in coastal marine ecosystems at contrasting sites

Abstract

Continental shelves cover less than 5% of the global ocean, but play a crucial role in marine biogeochemical cycling, since they account for 30% of primary production, 80% of organic matter burial, 50% of marine denitrification. Coastal waters biogeochemical cycling is subject to multiscale anthropogenic pressures ranging from climate change to nutrient loading input. The processes connecting the pelagic and benthic realms define the benthic– pelagic coupling (BPC) and comprises the physically, biologically and chemically mediated two-way exchange of matter (particulate and dissolved). Despite the importance of the benthic domain and the enhancement of models resolution, BPC is mostly approximated through a closure term. Moreover, data focusing on the BPC dynamics are sparse, hampering model parameterization and validation. The objectives of this study are: develop a parametrized numerical model addressing BPC and assess the skills of the 1DNEMO-BFM model in simulating the BPC in marine areas with different climatic characteristics. The benthic sub-model is based on two crucial parameters: the sinking velocity of particulate matter and the diffusion of inorganic matter at the benthic-pelagic interface. Beyond the apparent simplicity, the benthic sub-model has been calibrated considering a complex pelagic food web and for the main ecological and physical characteristic. The model has been implemented in three different sites: Gulf of Trieste, St Helena Bay (South Africa), Svinoy Fyr (Norway). For all the station, model results have been compared with observational data. Sensitivity tests have been performed, to statistically investigate the response of the benthic sub-model in changing