Assessment of macrobenthic communities of rocky intertidal zone from Zhejiang offshore islands with AZTI marine biotic index

Abstract

The structure of macrobenthic communities in island intertidal zones serves as an important indicator for assessing the health status of ecosystems. In recent years, the unregulated and extensive development and utilization of island resources in China, coupled with the continuous deterioration of the ecological environment in the surrounding marine areas of islands, have significantly impacted the health and stability of island ecosystems. Four investigations during spring (2018, 2021) and autumn (2017, 2020) of the Niushan Island intertidal zones and surrounding waters, located off the coast of Taizhou, Zhejiang, were conducted in this study. The purpose was to explore the external factors influencing the structure of intertidal macrobenthic communities and to assess the ecological status of the island. There was a clear vertical zonation observed in the distribution of the macrobenthic communities. During this survey, the eutrophication index improved, and the temperature, salinity, and suspended particulate matter exhibited seasonal fluctuations. Dissolved inorganic phosphorus and nitrate were the environmental factors that required special attention in coastal ecological monitoring, which significantly affected the distribution of the macrobenthic communities and was strongly correlated with the biotic indices and different ecological group biomasses. Most of the islands were classified as having a moderate status based on the Shannon-Wiener diversity index (H'). The AZTI Biotic Index (AMBI) and Multivariate AMBI (MAMBI) indicated that almost all islands were in good status, and the evaluation results demonstrated that the AMBI and MAMBI tended to overestimate the ecological status of the rocky intertidal zone. There was a significant correlation between the MAMBI and several traditional biological indices, suggesting that the MAMBI could be introduced as an evaluation indicator for the ecological status of rocky reefs. Nevertheless, it is important to consider the boundaries of different assessment levels.