Development of microbial community–based index of biotic integrity to evaluate the wetland ecosystem health in Suzhou, China

The development of microbial community–based biological indicators for assessing aquatic ecological status is urgently needed in heavily impaired regions, due to the local extinction of traditional indicator macro-organisms. The aim of this study was to develop and validate a microbial community–based index of biotic integrity (MC-IBI) to assess the health of wetlands in Suzhou, China. High-throughput sequencing was used to obtain information about microbial communities in wetlands and to investigate the health of the wetlands. When constructing the index, we selected what we considered were the most important environmental factors and biological parameters, and identified sensitive and tolerant species. We then used the index to evaluate the health of the inflows and outflows of 15 wetlands in Suzhou. The results showed that, of the 30 samples collected at the 10 impacted inflow sites, 2 were classified as "poor," 5 were "commonly," 18 were sub-healthy, and 5 were healthy; at the restored outflow sites, 24 were "healthy" and 6 were "sub-healthy." The health was worst at the inflows of wetlands that received agricultural effluent, followed by those that received industrial effluent, and was best at those that received urban effluent. The results from our study show that this newly developed MC-IBI gave reasonable evaluations of the health of wetland ecosystems. This application demonstrates that the evaluation system was feasible and we suggest that evaluations that further MC-IBI evaluation approaches should be developed further in the future.