ASSESSING BENTHIC IMPACTS OF ORGANIC ENRICHMENT FROM MARINE AQUACULTURE

Benthic observations were carried out at 22 stations in the Western Is les region of the Bay of Fundy on the east coast of Canada to evaluate impacts at salmon aquaculture sites. Eleven sites were located under salmon net-pens and 11 sites (reference or control locations) were at distances > 50 m from net-pens. Total S- and redox potential (Eh) in s urface sediment and benthic O-2 uptake and CO2 release were sensitive indicators of benthic organic enrichment. High variability between rep licate measurements of sediment gas exchange could reflect spatial pat chiness in sedimentation of fecal waste and food pellets under fish pe ns. Biomass of deposit feeders was significantly increased at cage sit es but total macrofauna biomass was similar at cage and reference loca tions. Surface sediment water content, modal grain size, pore water sa linity and sulfate, and total biomass of macrofauna were the least sen sitive indicators of enrichment.