A Mechanistic Modelling Approach to Predict Cold-Water Coral Biomass Based on Organic Matter and Hydrodynamics

Cold-water corals form complex three-dimensional structures on the seafloor, providing habitat for numerous species and act as a carbon cycling hotspot in the deep-sea. Although these ecosystems are recognized as important deep-sea habitats, our capacity to predict their distribution relies largely on statistical models in which coral occurrence is correlated to environmental variables such as temperature, salinity, rugosity and surface productivity. Here, we present the results of a mechanistic model in which we predict coral biomass based on coral physiology, suspended organic matter concentration and hydrodynamic forcing for the south eastern Rockall Bank (NE Atlantic). The hydrodynamic forcing is provided by a high-resolution ROMS (Regional Ocean Modelling System) model, which drives the transport of reactive suspended particulate organic matter in the region. A newly developed physiological cold-water coral model, which is based on coral respiration, assimilation efficiency and food uptake as key variables, is coupled to the organic matter transport model. Modelled coral food uptake depends on bottom current velocities and bottom particulate organic matter concentrations. We show this model approach can successfully predict cold-water coral biomass and our results are in line with biomass and benthic respiration observations in the study area and with a previous performed statistical distribution model. This mechanistic model can be used to investigate the effect of changing environmental conditions such as ocean temperature, surface production export or ocean currents on cold-water coral biomass distribution and can be applied to other study areas and/or coral species.