The environmental impact of mussel (Mytilus spp.) aquaculture at two Newfoundland sites

In this thesis I examine the environmental impacts of blue mussel ( Mytilus spp.) farming at two Newfoundland sites as one component of a larger interdisciplinary study of the environmental sustainability of shellfish aquaculture. Biodeposit production rates of individual mussels were comparable to values measured elsewhere using similar methods. The interaction between spatial and temporal variables was significant in explaining rates of biodeposit production. The impact of mussel farming on the benthos was addressed by examining the macrofaunal community structure at both sites relative to community structure at nearby reference sites. The farms were very different in terms of sediment and benthic macrofaunal community composition. Benthic macrofaunal communities in sediments with mean grain size larger than 500 mum at both farms showed differences in taxa and abundance relative to reference sites. Communities in sediments with mean grain size smaller than 500 mum also differed between farm and reference sites, and all of these stations (farm and reference) had sediments with negative redox values and were dominated by organisms indicative of organic enrichment. I also examine the problem of spatial and temporal scale, and demonstrate that by using statistical inference we have considerable confidence in the descriptions of benthic communities at the farms at each sampling time, but slightly less confidence in describing the communities throughout the year. Beyond the scale of an individual farm, more sampling would be required before any statement could be made with confidence about the species composition of the benthic communities of the entire region.