Abstract
Semi-enclosed bays have physical and chemical characteristics influenced by both land and sea systems and the quality of the benthic environment is always of great concern. Macrofauna are considered good indicators for evaluating the benthic ecological quality status owing to their biological characteristics. In this study, six biotic indices, namely the Shannon–Wiener diversity index (H′), Abundance-Biomass Comparison (ABC) curve, AZTI’s Marine Biotic Index (AMBI), multivariate-AMBI (M-AMBI), BOPA index, and BENTIX index, were used to evaluate the adaptability of different biological indices in the bioassessment of the benthic environment in a semi-enclosed bay. In the annual environmental assessment of the study area, the average values of the six indices (H′, ABC curve, AMBI, M-AMBI, BOPA, and BENTIX) were 4.494, 0.182, 2.433, 0.791, 0.033, and 3.813, respectively; accordingly, H′, M-AMBI, and BOPA met the high standards whereas the other indices met the good standards, indicating that the whole study bay was slightly disturbed and had good ecological quality. From the perspective of spatial variation, the benthic environment in the middle of the bay was better than that in the north; the environmental problems in the northeast were particularly noteworthy. In terms of temporal patterns, the benthic environment in winter and summer was significantly better than that in spring and autumn, with obvious seasonal differences. The present results indicate that the H′ and ABC curve based on benthic abundance and biomass should be avoided for environmental assessment in mariculture areas. AMBI and M-AMBI should be used with caution when the percentage of unassigned species is high, in which case H′ is the appropriate choice. When there are few unassigned species, M-AMBI is more conducive for accurate evaluation of the benthic environment than AMBI and H′.
Highlights
Compared with the pelagic ecosystems, benthic ecosystems have high species diversity
The results of the multiple biotic assessment methods showed that Jiaozhou Bay had a good benthic ecological quality status, which was consistent with the results of other studies (Yang et al, 2021; Yin et al, 2021)
R. philippinarum has been cultivated in Jiaozhou Bay since 2003 (Fan and Liu, 2016), becoming the dominant species of macrofauna until now (Wang et al, 2011)
Summary
Compared with the pelagic ecosystems, benthic ecosystems have high species diversity. Owing to the integration of the physical and chemical properties of land and ocean systems (Gao et al, 2021), the ecological environment has potential instability Environmental problems such as small tidal volume, poor water exchange capacity, and significant influence of human activities have become increasingly noteworthy (Lim et al, 2012; Peng et al, 2013). Shannon–Wiener diversity index (H ), Abundance-Biomass Comparison (ABC) curve, AZTI’s Marine Biotic Index (AMBI), multivariate-AMBI (M-AMBI), BOPA index, and BENTIX were used to evaluate the spatial and temporal variation of benthic ecological quality in Jiaozhou Bay. The results of the assessment are combined with environmental parameters to analyze the environmental quality of Jiaozhou Bay and further explore the impact of anthropogenic activities on the benthic environment. Considering the principles of the six indicators, the following assumptions are proposed: (1) The indexes based on biomass have limitations in shellfish farming areas. (2) M-AMBI is calculated by combining AMBI and H , so it can better explain the status of environmental quality
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