3D bio-physical model of the sympagic and planktonic productions in the Hudson Bay system

We present a first attempt of simulating the sympagic and planktonic production cycles in the Hudson Bay marine system (HBS) driven by ice cover duration and local hydrodynamics with the help of a 3D coupled biological–physical model. The simulation shows a marked spatial variability of ice and planktonic production and associated carbon fluxes, suggesting the co-existence of several sub-systems in the HBS. Among these, the “low ice–high mixing” Hudson Strait sub-system is characterized by high (low) planktonic (ice algae) production, with annual primary production reaching up to 150 g C m− 2 y− 1. In contrast, the “high ice–low mixing” conditions over Hudson Bay induce an annual primary production of ca. 10–40 g C m− 2 y− 1 with a strong and early ice algal bloom. New production generally prevails over the simulated system except along the coastal freshwater-influenced southeastern Hudson Bay and shallow Foxe Basin. In most of the HBS, summer conditions are characterized by the prominence of deep chlorophyll and biomass maxima (down to 60 m depth in the Hudson Bay) located near the nutricline. Finally, the residence time of the particulate organic matter and further export to the benthos appear driven by coupled advective and bathymetric effects.

Research highlights
► High spatio-temporal variability of primary production (PP) in Hudson Bay System.
► Control of ice cover duration and local hydrodynamics on sea ice and planktonic PP.
► Coupling/uncoupling between PP and carbon export. Higher accumulation in shallow areas.
► Identification of four sub-systems with different bio-physical characteristics.
► Biomass and production levels and spatial patterns in accordance with observed data.