| Summary: | [1] An important goal of WP2 was to develop mechanistic and predictive models for the distribution and metabolic activity of cold-water corals (CWCs) and deep-water sponges (DWS) and use these models to understand how their distribution is affected by the Atlantic Meridional Overturning Circulation (AMOC). [2] Output from hydrodynamic models (VIKING20 or ROMS-Agrif) was used to simulate transport of reactive organic matter in the water column around CWC reefs of DWS grounds. The approach is inspired by Soetaert et al. (2016), in which suspended organic matter dynamics above coral mounds was simulated. Here, we extend this methodology by having CWCs and DWS feeding on the suspended organic matter in the bottom layer using simple formulations for passive (CWC) and active (DWS) suspension feeding and metabolic activity. Physiological model formulation was based on data collected within ATLAS (Deliverables 2.1 and 2.2). [3] We focus on three ATLAS Study regions: 1) large CWC mounds, dominated and formed by the scleractinians Lophelia pertusa and Madrepora oculata, in the Logachev mound province in the south-eastern section of Rockall Bank, 2) coral gardens, dominated by the soft-coral Viminella flagellum, on Condor seamount, and 3) extensive sponge grounds, dominated by Geodia barretti along the east Canadian shelf break in Davis Strait. [4] We faced considerable computational challenges when developing the coupled models. CWC and DWS growth is slow, which implies that long simulation periods are needed to reach a (dynamic) steady state. Long simulation periods are not feasible given the high spatial and temporal (i.e. with tidal dynamics) resolution of the models. A 3-step solution procedure is proposed to tackle this issue, in which in step 1 initial suspended organic matter (OM) concentrations in the water column are calculated. In step 2, the bottom layer concentrations from step 1 are used to calculate initial concentrations for CWCs or DWS. In step 3, the coupled model is run with suspended organic matter ...
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