Assessment of macrobenthos community and ecological status of the Jiaozhou Bay, China

Jiaozhou Bay is one of the most economically and ecologically important semi-enclosed waters along the southern Yellow Sea coast of China. Anthropogenic activities like bivalve aquaculture, sewage discharge, and oil industry have severely impacted the bay environment in the past years. Macrobenthos plays an important role in monitoring marine ecosystem health. Species composition and community structure typically shift as a response to the effects of pollution and disturbance. In this study, macrobenthos community was characterized and assessed with the sediment samples collected from 15 stations in the Jiaozhou Bay in November 2018. Abundance, biomass, species composition, diversity and community structure along with environmental variables were determined to assess the benthic ecosystem health. The ecological status of the bay was also assessed by using abundance biomass comparison curve (ABC plot) and the widely used benthic indices AMBI and M-AMBI. The results showed that combination of five variables (water depth, Cha, Pha, sediment type, and biomass of different cultured bivalve species) were the main determinants for the macrobenthos community structure in the bay. Despite for most of the stations in the bay, relatively high species richness, evenness and diversity, and the undisturbed condition indicated by ABC plots and W statistics, the dominance of opportunistic polychaetes like Micronephthys oligobranchia could show that there is some degree of disturbance in the bay. ABC plot clearly indicated the disturbance of bivalve culture of Ruditapes philippinarum on the macrobenthos community at station J3. As a comparison, the highest abundance and species richness of macrobenthos at station J4 may indicate a positive role of oyster culture Magallana gigas on the improvement of ecological condition. The benthic indices AMBI and M-AMBI suggested that the benthic ecosystem of Jiaozhou Bay was slightly disturbed and the overall ecological status of the bay was in good condition.