A Wetland Mitigation Assessment and Macrophyte/Invertebrate Response to Wetland Creation Activities

Abstract

Two wetland mitigation sites in Wood County, Wisconsin, were monitored from February 1995 to October 1996. Information was collected for describing and monitoring abiotic and biotic wetland functions and to assist in determining success. This wetland study was instituted to complete the remaining 2 years of monitoring as required by a mitigation permit. The Fontaine Mitigation Site (FMS) (9.5 ha) and Nash Road Mitigation Site (NRMS) (14.6 ha) each consist of enhanced and created wetlands and a lake. Biological communities including herpetofauna, birds and mammals, invertebrates, fish, and aquatic vegetation were assessed through drift fences including associated pitfall and funnel traps, chorus surveys, observation surveys, incidental observations, phytomacrofauna samples, fyke nets and seines, and quadrats. Water quality data were collected for hydrology, temperature, rainfall, dissolved oxygen, conductivity, pH, alkalinity, and nutrients. Soils underlying each water body were mapped using Geographic Information Systems. During this 2 year period, 7 and >/= 6 species of small mammals, 10 and 12 species of herpetofauna, 10 and 9 species of fish, and 48 and 56 species of aquatic vegetation were identified on the FMS and NRMS, respectively. In 1995-1996, at least 200% more species of small mammals and 200% more species of herpetofauna were found on each site respectively, than in 1993-1994. In addition, 229% and 267% more aquatic vegetation species were identified on the FMS and NRMS, respectively, in 1995-1996 than in 1993-1994. Songbirds, waterbirds, prey-birds, and mammals comprised 83%, 13%, 3%, and 2% of the wildlife observed, respectively. Drift fences were found to be highly effective in assessing species richness for small mammals and herpetofauna. Almost 39% more anurans were captured in 1996 than 1995 at the NRMS; this increase can most likely be attributed to greater precipitation in 1996. The relatively rare Cope's frog (Hyla chrysoscelis) was documented at the NRMS with the chorus survey method. Water quality appeared to be largely influenced by underlying soils, geology, water source, and land use practices. The FMS lake is very productive, (high macrophyte biomass) most likely because of nutrients entering the system from overland flow and groundwater inflow from the agricultural field to the north. The west ponds at the FMS were very unproductive and acidic due to the high peat content ( organic acids) of underlying soils. Species richness, coverage, and biomass of submergent aquatic vegetation was lower at the NRMS lake than the FMS Lake due to a dense substrate which inhibited root penetration. However, emergent vegetation species richness and coverage was extensive within the wetland areas at the NRMS. Qualitative and quantitative biological and chemical results from this study and previous studies indicate the wetlands are fulfilling planned wetland functions and can therefore be considered successful.