Cost-effective monitoring of organic enrichment resulting from salmon mariculture

Abstract

Two methods of environmental monitoring proposed for the salmon mariculture industry are compared and contrasted on the basis of scientific and cost-effectiveness criteria: a technique based on macrofaunal community structure and one using process-oriented sediment geochemistry. For this purpose, field sampling was confined to one salmon farm and a nearby reference site in the Bay of Fundy. Both methods produced significant differences between farm and reference sites, as well as meeting other appropriate scientific criteria. The geochemical method was based on field measurements of sedimentary Eh, by redox electrode, and sedimentary sulphide after fixing the sediment in a sulphur anti-oxidant buffer and ion analyses with Ag/Ag sulphide and combination reference electrode. Both measures can be completed in the field from the sampling vessel. Results suggested that the geochemical method was of significantly lower cost than the technique based on macrofaunal community structure. This is because of the lengthy laboratory time required to determine the identity and abundance of macrofaunal taxa. Both methods can categorize the sedimentary organic impact as normal, oxic, hypoxic, or anoxic, which depends ultimately on the dominant microflora present. This, in turn, depends on the rate of carbon reaching the sediment, as well as its utilization by biological and physical processes.