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 tw o areas with intensive salmon net-pen aquaculture (Lime Kiln Bay, Bliss Har bour). A third embayment (Deadmans Harbour), which lacked significant aquac ulture activity. served as a reference site. Changes in benthic community s tructure were investigated using multivariate, distributional. and univaria te analyses. Such changes reflect cumulative stress From various sources, i ncluding organic enrichment and chemical therapeutants. Changes at the Dead mans Harbour reference site indicated a general improvement in ecosystem qu ality during the study period. Lime Kiln Bay experienced an increase in aqu aculture activity during the first few years. Followed by a complete cessat ion in 1998. Analyses indicated increased biological stress on the benthic community, suggesting major environmental alterations did take place in tha t bay. Diversity declined significantly between 1994 and 1995. with a corre sponding significant increase in sediment organic content. Analysis of indi cator species corroborated the enrichment trend. Sedimentary microbial biom ass and organic matter concentrations decreased from 1997 to 1999, reflecti ng the cessation of fish farming, but the benthos did not recover during th is period. IL is concluded that benthic impact in Lime Kiln Bay persisted u ntil 1999 even though organic loading decreased. Enrichment levels in Bliss Harbour were elevated From the beginning of the study onwards and the impa ct persisted throughout the study. The observed differences in community st ructure within the three embayments were not attributable to differences in sediment types, temperature. salinity. or water depth. (C) 2001 Internatio nal Council for the Exploration of the Sea.