| Marshes may function by regulating nutrient flux between many aquatic and terrestrial ecosystems. Few studies have quantified the cycling and storage of nitrogen and phosphorus in freshwater marshes. Plant nutrient uptake and litter mineralization are two of the primary mechanisms a wetland might control nutrient cycles and water quality. The importance of these processes relative to the total flux of nutrients through a wetland is rarely known. This study quantified the flux and retention of N and P through a marsh, and evaluated the role of emergent plants in controlling nutrient retention.; Hydrologic, non-gaseous N, and P mass balance data were developed from studies conducted at Pentwater Marsh, Pentwater Twp., MI USA (43(DEGREES) 46' N, 86(DEGREES) W). On an annual basis, about 10% of the inorganic-N inputs were removed by the marsh. An export of organic-N (27.6%) occurred, but organic-N export was not significantly greater than inorganic-N retention. Total-P and reactive-P were removed by the marsh (30.4% and 13.8% respectively). For both N and P, the greatest retention occurred during the growing season, suggesting biological control of removal processes.; Biomass production in 6 emergent and wet meadow communities (Sparganium eurycarpum, Scirpus validus, Typha latifolia, Calamagrostis canadensis, Carex stricta, and Carex aquatilis) was studied using harvest techniques. Tissue N and P concentrations and the biomass data were used to evaluate the role of vegetation in marsh nutrient cycles. Maximum shoot N content ranged from 4.8 g m('-2) to 7.9 g m('-2), and P content from 0.6 g m('-2) to 2.0 g m('-2). Average production and nutrient uptake rates were lower in the meadow than the emergent zone. Annually, only 2% of the N and 15% of the P inputs are accounted for in the August shoot biomass. However, shoot biomass could account for 25% of the inorganic-N and 59% of the total-P removed from the rivers.; N and P mineralization rates were greatest in the emergent zone. In emergent areas, as much as 88% of N and P in litter may be mineralized annually. Nutrient mineralization in the meadow zone can be only 20% that of the emergent zone. |
