Situated in an anthropogenic environment, urban wetlands are more susceptible to nutrient runoff and polluted storm water compared to wetlands in more natural settings but can provide important benefits, such as biodiversity and nutrient cycling. In August 2017, two riparian wetlands with differential water sources were restored in Louisville, Kentucky. The wetlands are 60 meters apart; however, Wetland 1 receives primarily runoff, whereas Wetland 2 receives more groundwater, creating two different potential environments for macro-invertebrate communities to develop. Water quality measurements can provide information on urban influences and help to predict biodiversity progression of each wetland. Conductivity, temperature, pH, nitrate, turbidity, and dissolved oxygen were measured monthly using YSI Pro-DSS. Alkalinity and orthophosphate were measured from water samples using a Hach colorimetric kit. Water-quality data were analyzed to predict expected macro-invertebrate abundance and diversity.
Results/Conclusions
The wetlands experienced a summertime hypoxic period following restoration, reaching minimum dissolved oxygen levels of 5.2 mg/L in Wetland 1 and 2.4 mg/L in Wetland 2. Warmer water temperatures, lack of cooler groundwater discharge, and increased respiration of algal biomass can account for the hypoxia. Mean dissolved oxygen levels in Wetland 2 were lower than Wetland 1 overall (7.9 vs. 9.4 mg/L, respectively), suggesting that a macro-invertebrate population more tolerant to lower oxygen levels may develop in Wetland 2. Placement of the wetlands in relation to the underlying hydrogeology can create differences in nutrient loading and conductivity. Wetland 2 is supplied by groundwater. Therefore, the water quality may be different and so will the macro-invertebrate community. Based on lower dissolved oxygen levels and higher maximum conductivity in Wetland 2 of 1275 uS/cm vs. 1081 uS/cm in Wetland 1, we can predict that the macro-invertebrate population may be more pollutant tolerant in Wetland 2, thereby supporting a less diverse community. Future research will include macro-invertebrate collection from multiple sub-habitats and identification to family level to test these predictions. An understanding of the effects of water quality on macro-invertebrate communities in restored urban wetlands can guide expectations of biodiversity in restoration efforts.