Assessment of regional benthic impact of salmon mariculture within the Letang Inlet, Bay of Fundy

Between 1994 and 1999, impact on the benthic fauna has been evaluated in two areas with intensive salmon net-pen aquaculture (Lime Kiln Bay, Bliss Harbour). A third embayment (Deadmans Harbour), which lacked significant aquaculture activity, served as a reference site. Changes in benthic community structure were investigated using multivariate, distributional, and univariate analyses. Such changes reflect cumulative stress from various sources, including organic enrichment and chemical therapeutants. Changes at the Deadmans Harbour reference site indicated a general improvement in ecosystem quality during the study period. Lime Kiln Bay experienced an increase in aquaculture activity during the first few years, followed by a complete cessation in 1998. Analyses indicated increased biological stress on the benthic community, suggesting major environmental alterations did take place in that bay. Diversity declined significantly between 1994 and 1995, with a corresponding significant increase in sediment organic content. Analysis of indicator species corroborated the enrichment trend. Sedimentary microbial biomass and organic matter concentrations decreased from 1997 to 1999, reflecting the cessation of fish farming, but the benthos did not recover during this period. It is concluded that benthic impact in Lime Kiln Bay persisted until 1999 even though organic loading decreased. Enrichment levels in Bliss Harbour were elevated from the beginning of the study onwards and the impact persisted throughout the study. The observed differences in community structure within the three embayments were not attributable to differences in sediment types, temperature, salinity, or water depth.