Application of a biotic index to assess natural and constructed riparian wetlands in an estuary

In an estuary, large numbers of riparian wetlands have high conservation values, and it is essential for the conservation of these wetlands to assess their ecological conditions. A wetland zooplankton index (WZI) was modified to assess the ecological conditions of the riparian wetlands (both natural and constructed) of the Pearl River Estuary (PRE), including water quality, presence/absence of macrophytes, soil texture, wetland origin, wetland location and zooplankton distribution. A water quality index (WQI) is established to compare the accuracy of the WZI to conventional community indices. The results show that although some conventional community indices show no significant differences between natural and constructed riparian wetlands, significantly higher scores of WZI and WQI are found in the constructed riparian wetlands compared to the natural riparian wetlands. The results of a regression analysis with Pearson's correlations show that WZI was significantly correlated with the WQI compared with the conventional community indices. The results of this study indicate that the WZI can more accurately reflect the ecological conditions of wetlands than the conventional community indices. Although a better water quality (lower WQI value) is found in natural riparian wetlands than in the constructed riparian wetlands, the ecological conditions of natural riparian wetlands are significantly worse than those of constructed riparian wetlands, based on the scores of the WZI; these data suggest that the origin of the wetland may cause a deterioration in the water quality but is unlikely to cause a degradation of the wetlands. This study shows that the WZI is an effective tool to assess the ecological condition of the riparian wetlands and that it can be used to guide programs for the conservation, restoration and the construction of wetland networks in the estuary.