Assessment of the benthic ecological quality status (EcoQs) of Laizhou Bay (China) with an integrated AMBI, M−AMBI, BENTIX, BO2A and feeding evenness index

Abstract

With increasing impacts of climate change and human activities on marine ecosystems, accurate assessment of benthic ecological quality status (EcoQs) has become increasingly important for ecosystem management and restoration. Here, we used five macrobenthos-based biotic indices (the AZTI marine biotic index (AMBI), multivariate AZTI marine biotic index (M−AMBI), benthic index (BENTIX), benthic opportunistic annelid amphipod index (BO2A) and feeding evenness index (jFD)) to assess the EcoQs of Laizhou Bay in Bohai Sea, China, and examine the consistency among indices. The five biotic indices were then combined and integrated in a composite index to assess the benthic EcoQs of Laizhou Bay, and determine which areas had acceptable or unacceptable EcoQs. The EcoQs of Laizhou Bay differed depending on the selected index, and the agreement among indices was low according to Kappa analysis. AMBI and BO2A indicated that the EcoQs of all sampled stations in Laizhou Bay were acceptable, whereas M−AMBI, BENTIX and jFD indicated that the stations with acceptable EcoQs accounted for 69.56%, 82.61% and 52.1%, respectively. The final EcoQs based on a composite of the five biotic indices indicated that 83.78% of the total study area of Laizhou Bay was acceptable, while the unacceptable areas were distributed mainly in the estuarine area (e.g., Xiaoqing River and Mi River). Moreover, all five biotic indices and four species diversity indices (richness, Shannon, Simpson and Pielou indices) indicated that the area with acceptable EcoQs showed higher values than the area with unacceptable EcoQs. The functional diversity indices (FRic, FDis and RaoQ) also showed significantly higher values in acceptable than unacceptable areas. We argue that the use of our composite index combining multiple indices to assess benthic ecological quality yields more accurate results than the use of individual indices, and additionally provides valuable information for ecosystem management.