Macrozoobenthic Diversity along an Oxygen Gradient in the Deep Trough of the Gulf of St. Lawrence (Canada)

In 2015, we studied the macrozoobenthic community composition along a dissolved oxygen gradient in deep trough of Gulf St. Lawrence (Canada). We sampled seabed at nine stations using box corers (three replicates per station), starting outer and ending Lower River Estuary. found four different communities dominated by polychaetes, crustaceans, molluscs, with emphasis shifting from mollusc to polychaete as saturation decreased. Contrary our expectations, furthest upstream estuary lowest levels had highest species diversity, also density biomass values. Key genera hypoxic zone included bivalves (Thyasira), cumaceans (Diastylis), amphipods (Harpinia), polychaetes such Ampharete, Ceratocephale, Galathowenia, Trochochaeta. attribute this stability environmental conditions absence stress, where constant supply oxygen, even low concentrations, seems be more important than absolute concentration.