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Sedimentation of phosphorus and nitrogen from the water column was measured with six traps deployed in each wetland, three in the deep and three in the shallow strata. Traps had a height-diameter ratio of 3, thus preventing resuspension of trapped particles (Blomquist and Kofoed 1981). Trap contents were collected on the three sampling dates and analyzed by the Minnesota Department of Agriculture Chemistry Laboratory (MNDA-CL) for total phosphorus and nitrogen (APHA 1992). Traps collected on 19 May were deployed 26 days, 23 June for 35 days, and 4 August for 42 days. Results were corrected for water column nutrient concentrations and number of days traps were deployed. Results are expressed as mg•m^-2•day^-1.

Five sediment cores were taken on each date at random locations in both deep and shallow strata using a KB corer. The top 3 cm of the core (surface to 3 cm deep) was placed on ice and returned to the lab. Each cross section was homogenized with a mortar and pestle, dried at 60° C for 24 hrs, placed in a desiccator for one hour, and analyzed for total phosphorus and nitrogen content by the North Dakota State University Soil and Water Testing Laboratory (NDSU-SWTL) (APHA 1992). Results are expressed as nitrogen and phosphorus•m^-2.

Concentrations of interstitial phosphorus and nitrogen were determined on the three sampling dates using four interstitial samplers, two deployed in the deep strata and two in the shallow strata in each wetland. Samples were analyzed by MNDA-CL for total phosphorus and nitrogen concentrations (APHA 1992). Results are expressed as total nitrogen and phosphorus•L^-1.

Turbidity was measured in the field on six dates with a portable nephelometer. On three dates, four water samples were collected in each wetland, two in the deep stratum and two in the shallow stratum. Additional water samples were collected in the deep stratum on six other dates. The water samples were analyzed by MDA-CL for chlorophyll a, total phosphorus, and total nitrogen (APHA 1992). Phytoplankton biomass was estimated from chlorophyll a concentrations (Reynolds 1984), and phosphorus and nitrogen content of phytoplankton was determined from biomass (Behrendt 1990). Results are expressed as total phytoplankton biomass and nitrogen and phosphorus in phytoplankton•L^-1.

Invertebrate samples were collected in both shallow and mid-depth strata with a modified Gerking sampler at five random locations in each stratum on each date, and samples were concentrated with a 68 µm funnel. Benthic invertebrates were sampled on each date at five random locations in the deep stratum using an Ekman sampler and rinsed through a 0.5 mm mesh. Planktonic invertebrates in the deep strata were collected with a column sampler (Swanson 1978) at five random locations on each date and rinsed through a 68 µm mesh. All samples were preserved in 70% ethanol.

Invertebrates were identified to the lowest feasible taxonomic group and counted. Average lengths of invertebrate taxa were determined for each date using an image analysis system, and individuals in each taxon were measured until standard errors were < 10% of the mean. Invertebrate biomass was then estimated from length-weight equations of Dumont et al. (1975), Smock (1980), McCauley (1984), Stein et al. (1984), Traina and von Ende (1992), and Noraker and Zimmer (unpublished data). Nitrogen and phosphorus concentrations in invertebrates were taken from the literature (Peters and Rigler 1973, Nakashima and Legget 1980, Behrendt 1990, Hessen and Lyche 1991). Results are expressed as invertebrate biomass•ha^-1 and nitrogen and phosphorus contained in aquatic invertebrates•ha^-1. We also determined the amount of phosphorus and nitrogen•L^-1 in aquatic invertebrates collected in the water column (cladocerans, cyclopods, etc.), allowing estimation of nutrients in other seston.

Nutrients in "other seston" was estimated by subtracting concentrations of nutrients contained in phytoplankton and zooplankton•L^-1 (described above) from the total water-column nutrient concentration•L^-1. Other seston represents nitrogen and phosphorus in particulate matter other than phytoplankton and zooplankton, as well as dissolved forms.

Samples for submersed and emergent macrophytes, periphyton, and metaphyton were collected in the shallow and mid-depth strata with a modified stovepipe sampler. We used an Ekman sampler to collect samples in the deep stratum. Five samples were collected at random locations on each date within each stratum, with only above-sediment biomass collected. All material was placed in plastic bags and transported to the lab on ice for sorting. Aquatic invertebrates and metaphyton were removed from samples by hand, and periphyton was separated from macrophytes by lightly scrubbing and rinsing with distilled water (Raschke and Rusanowski 1984). Macrophyton, metaphyton, and periphyton were placed in aluminum drying pans, dried at 60° C for 24 hours, cooled in a desiccator for 1 hour, and weighed (Raschke and Rusanowski 1984). Samples were analyzed by NDSU-SWTL for total nitrogen and phosphorus•g^-L (APHA 1992). Results are expressed as biomass, nitrogen, and phosphorus•ha^-1 for metaphyton, macrophyton, and periphyton.

Fathead minnows were sampled in Sagebraten from 19 May through 4 August at approximately two week intervals. Fish were sampled using 1 m-diameter pop-nets (Dewey et al. 1989) with 0.5 mm (bar measure) mesh. Fifteen samples were taken on each date at random locations in each stratum, and captured fish were recorded as either juvenile (<40 mm total length) or adults (>40 mm total length). We measured total length (mm) and wet mass (nearest .01 g) of 300 randomly selected individuals on each date, and average weights were determined for both juvenile and adult fish. We then determined the average number of fish•m^-2 for each stratum from the 15 samples, and estimated the total population size by summing the average density multiplied by area for each stratum. Biomass was estimated by multiplying the number of fish by their average weight. Amounts of nitrogen and phosphorus contained in the fish population were assumed to be 2.5% and .5% of wet mass, respectively (Schindler and Eby 1997). Results are expressed as number of juvenile and adult fathead minnows•ha^-1, total fish biomass•ha^-1, and nitrogen and phosphorus in fathead minnows•ha^-1.

Estimating total phosphorus and nitrogen in each wetland required estimates of sediment area and water volume of each stratum. We used a TopconŽ total station to construct a basin morphometry map for each wetland, and then estimated area of sediment and water volume of each stratum using Surfer software (Golden Software 1997). Biomass•m^-2 of macrophyton, periphyton, metaphyton, phytoplankton, aquatic invertebrates, and fathead minnows were then extrapolated to estimate total biomass•ha^-1 for each category. Phosphorus and nitrogen concentrations per unit biomass were then used to estimate the amount of nutrients in each pool•ha^-1. Estimates for each pool were then summed to determine total amounts of phosphorus and nitrogen•ha^-1 in each wetland.