Historically, coastal wetlands along the western Lake Erie basin supported a wide range of ecosystem functions including nutrient retention and biodiversity support. Remaining coastal wetlands are diked, severing hydrologic connection and limiting ecosystem functions. Growing concern over increased frequency and intensity of harmful algal blooms has prompted hydrologic reconnection of coastal wetlands to Lake Erie. In particular, approximately 12 km2 of coastal wetlands in Ottawa National Wildlife Refuge (ONWR) within the Maumee Area of Concern are being reconnected. Reconnecting wetlands is predicted to improve habitat and water quality in the long-term, but there may be short-term trade-offs to biodiversity. For example, high levels of nitrogen (N) and phosphorus (P) frequently reduce biodiversity of key components of the aquatic food web, including macroinvertebrates. We predicted that 1) nutrient retention would be higher in reconnected wetlands, and 2) taxonomic and functional macroinvertebrate diversity and richness would be lower in reconnected as a result of higher nutrients. In 6 reconnected and 6 diked coastal wetlands in ONWR, we compared total N and P as indicators of nutrient retention. Additionally, we compared taxonomic and functional macroinvertebrate diversity and richness between reconnected and diked wetlands to identify whether there were changes in biodiversity.
Results/Conclusions
In 2016, total N was lower in reconnected than in diked wetlands (p < 0.001). Total P was also lower in reconnected than in diked wetlands (p = 0.04). However, nutrients were similar between reconnected and diked wetlands in 2017 and similar to nutrient levels within diked wetlands in 2016, which may suggest reconnected wetlands had higher nutrient retention in 2017. In 2016, macroinvertebrate taxonomic diversity and richness were similar, but in 2017, reconnected wetlands had higher taxonomic diversity and richness in summer (p = 0.019) and fall (p = 0.01). Functional diversity and richness were similar between wetland types in both years. Together, these findings suggest that there may not be trade-offs between nutrient retention and macroinvertebrate biodiversity in coastal wetlands in the short-term.