Low benthic impact of an offshore mussel farm in ？les-de-la-Madeleine, eastern Canada

ABSTRACT: Ensuring sustainable management of the emerging open-ocean aquaculture industry requires an understanding of how this activity interacts with the surrounding environment. We examined the effects of an offshore mussel farm on sedimentation rates, sediment sulfide levels and macro-infaunal communities near ？les-de-la-Madeleine, eastern Canada. The farm had been in production for 6 yr and is located in a deep (19 m) high-energy environment. The impacts were examined for 2 densities of mussels (standard and double) and at different periods of the year. There was no sign of excessive organic enrichment or a clear pattern of a significantly modified benthic environment. However, some organisms likely benefited from the biodeposits and fall-off of mussels (and associated communities), and the farm presumably induced heterogeneity in the distribution of infaunal communities, likely due to variation in the dispersion of biodeposits caused by the structure of the longlines and local hydrodynamics. Annual and interannual variability appear stronger than the influence of the farm, and no detrimental effects are suspected. This study provides baseline information about the limited documented effects of open-ocean bivalve aquaculture on the benthic environment.