Characterization of the Spatial Pattern of Benthic Sulfide Concentrations at Six Salmon Farms in Southwestern New Brunswick, Bay of Fundy

Résumé du livre

Spatially-intensive sediment sulfide sampling surveys were conducted during the summer months at six salmon farms in southwestern New Brunswick, Bay of Fundy, Canada. One of the six farms was also sampled during the following spring to examine seasonal changes. Grab samples were taken at 20−57 locations around the fish cages and up to 100−150 m away. The sulfide distribution under farms was spatially patchy. The highest sulfide levels measured were generally found near cages; however, sulfide levels were low near most cages, as well as at most locations away from cages. At most farms, any areas of hypoxic sediments were mostly confined within the cage array areas, and were not found beyond 60-100 m from the cage edges. Only two farms had any anoxic sediments; at one of these, some anoxic sediments were located outside the cage array. At four of the six farms, the mean sulfide levels from the annual regulatory monitoring (conducted in August-October) were significantly different from the mean of the summer survey samples taken nearest to the regulatory monitoring locations. This may have been due to differences in the dates between the sampling and monitoring events and/or small-scale spatial heterogeneity of the sulfide levels. The one farm that was sampled both in summer and the following spring showed different sulfide levels on the two dates, with considerably lower levels in the spring