Preserving or restoring wetlands may help reduce nonpoint-source pollution. Wetlands can act as filters Few studies have measured removal of pollutants by restored wetremoving particulate material, as sinks accumulating nulands that receive highly variable inflows. We used automated flowproportional sampling to monitor the removal of nutrients and sustrients, or as transformers converting nutrients to differ- extensively studied for their use in wastewater treatment although 30% of the total organic C input was removed. For the (Hammer, 1989; Kadlec and Knight, 1996). However, entire two-year period, the wetland removed 25% of the ammonium, wetlands constructed for wastewater treatment usually 52% of the nitrate, and 34% of the organic C it received, but there receive measured and controlled inflows of wastewater. was no significant net removal of total suspended solids (TSS) orAlso, the outflows from wastewater treatment wetlands other forms of N and P. Although the variability of inflow may have are usually monitored to check the wetland's perfordecreased the capacity of the wetland to remove materials, the wetland mance. Therefore, much is known about the capabilities still reduced nonpoint-source pollution.

A three-year study of aboveground biomass and nutrient dynamics in twelve restored depressional wetlands of different ages demonstrated significant annual variability among sites. Annual variations appeared to be primarily due to differences in hydrologic conditions over the three years of the study. Differences among wetlands were not related to time since restoration. When data for all sites were combined, annual differences in biomass and most measurements of nutrients (concentrations and standing stocks) did not, however, differ significantly. These results suggest that differences that are measured at individual wetland sites may be less important at the landscape level. Biomass decreased from the outer temporary to inner submersed zone, and there were few differences among wetlands when the temporary, seasonal, and submersed zones were compared. Nutrient concentrations in the plant biomass increased from the temporary zone to the submersed zone, resulting in few differences in nutrient standing crops across zones. Results from this study demonstrate that some measurements of restoration success (i.e., biomass production) should be used cautiously because they are likely to be highly variable among sites and across years and thus may be of limited use in post-restoration monitoring. Other ecosystem parameters (e.g., nutrient concentrations of biomass) are much more constant spatially and temporally, indicating that nutrient cycling processes in vegetation were established quickly following restoration. Nutrient characteristics of wetland vegetation thus may be a useful metric for evaluating restoration success or failure.