Ecosystem Interactions with Mussel Culture in Newfoundland Coastal Waters

No abstracts are to be cited without prior reference to the author.

Environmental impact of bivalve aquaculture and requirements for sustainable bivalve production are closely linked. Shellfish aquaculture depends on the environment to supply food and remove degradation and waste products. Cultured bivalves consume plankton that are produced over a much wider area than the physical footprint of the shellfish farm resulting in localized, high rates of organic matter deposition and remineralization in both water column and sediments. There is thus the potential for feedback from the waste products of animal metabolism to the production of autotrophic and heterotrophic bivalve prey. We examined the impact of high density shellfish culture on pelagic and benthic ecosystem processes in a two-year field study of mussel farms and nearby reference sites on the northeast coast of the Island of Newfoundland, Canada. The farms were located in sheltered bays and differed in sustainable stocking density and time to market. The biomass of microplankton, but not mesozooplankton, differed significantly between farm and reference sites, with in-farm microplankton being up to two-fold greater than in other Newfoundland coastal waters. Although sediment organic matter, redox, and sulfide levels did not differ between farms and reference sites, there were differences in benthic infauna, and higher rates of sediment-to-water fluxes of NH4 + and PO4 + . Our results indicate the potential for significant feedback from mussels on in situ planktonic processes which in turn influence mussel production. Site-specific responses indicate however, that bathymetry and stratification play a key role in determining the magnitude of the feedback and hence system productivity.