The influence of macrophytes, disease, and restoration on freshwater ecosystems

This dissertation investigates nitrogen processing at multiple scales beginning at the stream reach, the influence of zooplankton on lakes, and finally the influence of human restoration of wetlands at the watershed scale. Multiple approaches are applied to test hypotheses that explain and describe processes that ecologists and environmental managers can apply to better understand and improve aquatic ecosystem function.; Agricultural streams are thought to have poor capacity for nitrogen retention because of excessive nitrogen concentrations and disturbance. However, a pro-active ecosystem ecology approach can identify ways of using the unique characteristics of agricultural streams to decrease nitrogen pollution. We tested the hypothesis that a microbial process, denitrification, is related to the presence of aquatic vascular plants (macrophytes) in stream sediments and whether this process can provide a measurable sink for nitrogen pollution. The results suggest that Black Earth Creek, because of the abundance of macrophytes, is capable of providing a valuable ecosystem service to remove nitrogen through sediment denitrification.; The effects of fungal infection, Polycaryum laeve, on the nutrient composition of a crustacean zooplankton Daphnia pulicaria is a new area of research. We compared the size, fatty acid, and stoichiometric (carbon, nitrogen, and phosphorus) differences of Daphnia that are infected by a highly prevalent chytrid fungus with those that are healthy to test the hypothesis that parasites diminish the nutrient composition of Daphnia. We found that infected Daphnia are smaller, lack essential fatty acids, and have a lower N:C ratio, compared to healthy Daphnia. Our results suggest that disease may be an important factor in determining zooplankton nutrient composition.; Government easement programs are being used to increase wetland area. However, few are formally evaluated. We test the hypothesis that a government easement program will increase wetland area and maintain landowner satisfaction with the program. We found that the wetlands reserve program successfully restores wetland habitat from marginal agricultural land to primarily wet meadow. Landowners that participated in WRP were satisfied with the process and outcomes of the restoration activities. By increasing wetland area, the WRP and other easement programs can improve ecosystem services including nitrogen retention at the watershed scale.