The influence of a rainbow trout (Oncorhynchus mykiss ) cage farm on the benthic environment and invertebrate fauna of Lake 375, Experimental Lakes Area.

摘要

I examined the development of effects from an experimental rainbow trout farm on sediment nutrients; metals; pore-water ammonia; sulfide; and zoobenthic density, richness, and biomass across the spatial gradient in organic loading created with distance from the farm. Pore-water total ammonia was the first variable to respond. Beneath the farm it reached 481.6 times the concentration in reference sediment (77 mg L-1) by September 2004. At this time sediment organic carbon, nitrogen, and phosphorus were 3.2, 4.5, and 18.6 times the reference sediment concentration, respectively. Invertebrate density was significantly reduced under the cage, reaching 442 individuals m-2 in October 2003 vs. 11089 individuals m-2 at reference stations. Thereafter, density remained below 600 individuals m-2. Taxa richness was also depressed, but biomass was variable. Variables with the most potential for incorporation into monitoring schemes included total ammonia and invertebrate density. The effects of farming were localized, extending only 5 m beyond the cage edge.