Analysis of benthic invertebrate communities downstream of land-based aquaculture facilities in Nova Scotia, Canada

Abstract

Land-based aquaculture facilities are located throughout Nova Scotia. They are generally located beside streams, to which they discharge large quantities of used water, and their discharges are usually only monitored for some nutrient parameters at varying frequencies. However, intermittent water sampling is not sufficient to assess any aquatic ecosystem health impacts resulting from discharges. Monitoring benthic invertebrate populations’ characteristics can be used to assess aquatic ecosystem health, and this study evaluated the benthic invertebrate population characteristics downstream of five land-based aquaculture facilities in Nova Scotia. Total abundance and relative abundance of Chironomidae were elevated, while number of taxa, relative abundance of Ephemeroptera + Plecoptera + Trichoptera (EPT), Pielou’s evenness and diversity were reduced at three out of the five sampling locations. Furthermore, a comparison of populations of benthic invertebrates downstream of the facilities to those predicted by the Canadian Aquatic Biomonitoring Network Atlantic reference condition approach model revealed that population characteristics downstream at two out of the five facilities were noticeably different than those predicted by the model. Those population changes are consistent with other studies where nutrient enrichment was correlated to abundance and diversity.