Development of a multi-metric index based on aquatic invertebrates to assess floodplain wetland condition

The construction of levees breaks the connection of floodplains with river channels. Few assessments have examined the impacts on aquatic ecosystems. We developed a multi-metric index (MMI) based on aquatic invertebrates to assess floodplain wetland condition in the Wusuli River, northeastern China. We sampled the aquatic invertebrate communities in 18 floodplain wetlands along the Wusuli River including wetlands from headwater, middle river, and downstream reaches. Each site included paired wetlands with a wetland connected to the river floodplain and a wetland isolated from the floodplain by levees. Metrics related to the aquatic invertebrate community were selected as candidate metrics for the MMI. Then, a range test, discrimination analysis, and correlation analytics were used to select the candidate metrics based on their ability to distinguish reference and isolated wetlands. Four core indicators were selected to build the MMI: total number of taxa, %Gastropoda, Pielou's index, and %Collector-Gatherers. Four ordinal rating categories were defined: poor, fair, good, and excellent condition. The results showed 88.9% of the levee-isolated wetlands, which were identified as being in poor or fair condition. Levee construction has a consistent negative impact on floodplain wetland condition. Our MMI provides a biomonitoring way to determine the success of restoration strategies.