The impact assessment of cage aquaculture on benthic communities along the south eastern Black Sea

The present study was conducted to examine the impact of cage aquaculture on benthic communities in coastal areas (depth ۲۵ to ۵۰ m) from fish farming operations located along the southeastern Black Sea (Ordu-Perşembe, Trabzon-Yomra and Rize central). Sampling was conducted seasonally from April ۲۰۰۷ to ۲۰۰۹. Sediment samples were taken using Ekman Grab (box core- ۰.۰۴ m۲). Temperature, salinity, and water velocity were periodically measured to determine influencing sedimentary organic matter in the sediment, oxygenation, and anoxic conditions. In addition, grain size of sediment, organic carbon content, and distribution of benthic communities were investigated. In order to determine benthic impact of fish farms on the region, Shannon – Wiener diversity index (H’), AMBI (AZTI Marine Biotic Index) and M-AMBI (Multivariate- Marine Biotic Index) indices were used. Results of current study showed that benthic zone ecological quality of stations with number ۰۱, ۰۲, ۰۳, and ۰۴ at Ordu-Perşembefish-farming habitat was found to be very low. In autumn ۲۰۰۸, there were ۳ species which belonged to Capitella capitata (۸۴۴ individuals/m۲), Capitella sp. (۱۳۳ individuals/m۲), and Heteromastus filliformis (۳۱۱ individuals/m۲) at OP-۰۱ station. In addition, the impact of Trabzon-Yomra fish-farming activity on benthic communities was low. The degree of exposure for Rize fish-farming area in all seasons was quite low, which was not a significant negative impact.