Offshore platforms: comparison of five benthic indicators for assessing the macrozoobenthic stress levels

Abstract

Within the European Water Framework Directive, many studies have been conducted to evaluate the sensitivity/robustness of a variety of indices in relation to natural or anthropogenic disturbance events. However, these indices have rarely been applied to verify the impacts of disturbances in offshore environments, though the Marine Strategy Framework Directive recommends their use for assessing benthic community conditions and functionality. The aim of this paper was to determine which biotic indicator performed the best for detecting the impacts of offshore structures on benthic populations in the Adriatic Sea. The impacts of four rigs were investigated six months after their installation, and the H', AMBI, m-AMBI, BENTIX, and BOPA indices were assessed. Although these five indices delivered some contradictory results because of the differences in their structure and discrepancies in their assignment of species sensitivity, the BENTIX, H' and BOPA indices appear to evaluate stress levels better than the AMBI and m-AMBI indices, which tend to provide results that are slightly overly optimistic.

Keywords: Biotic indices; Macrozoobenthic communities; Offshore platforms; Stress evaluation.