Assessing benthic ecological status in subtropical islands, China using AMBI and Bentix indices

Assessment of the ecological quality status is important for environmental protection and management. Benthic sensitivity-based indices have been considered as effective indicators of ecosystem health assessment. In this paper, two benthic sensitivity-based indices, AMBI and Bentix, were used to assess the benthic ecological status of soft-bottom intertidal zones in China's subtropical islands according to the data obtained in spring, 2007. Simultaneously, the assessment results were compared with the sediment quality in order to test the applicability of the indices for island eco-environmental quality assessment. The results showed that 246 species of macrobenthos were identified in the sampling sites. In the intertidal zone of Meizhou Island, dominant species were tolerant, which accounted for 58.7% of the total individuals. In the other intertidal transects, the dominant species were sensitive, but the percentages of tolerant species were high in the intertidal zone of estuarine islands. The results also showed that the benthic ecological status of most intertidal zones studied was high or good, except for the middle tidal zone of Meizhou Island where it was moderate. The two biotic indices were generally correlated with the contents of heavy metals and petroleum in the sediments, which indicated that the two indices could be used to detect the environmental changes related to pollution in a wide range. However, it seems that the AMBI assessment results more reasonably approximated those of the concurrent sediment quality survey than the performance of Bentix.