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Abstract
Here we evaluate field-to-stream water quality gradients across a forested alluvial swamp and through a ditched wetland swale on the same working farm. During 2016 and 2017, soil, surface water, and shallow groundwater samples were collected on this farm and analyzed for nitrate + nitrate (nitrate), total phosphorus (TP), and microbial species richness and biovolume. Significant nitrate and TP reduction occurred as shallow groundwater and surface water moved from the farm through an alluvial swamp. Conversely, a ditched depressional wetland swale with cropping on the margins did not significantly alter nutrient concentrations between where water enters the wetland and its discharge point. While pollutant additions were similar into both types of floodplain wetlands, water quality improvements were distinct in the alluvial swamp. Cyanobacteria algal abundance and biovolume correlated positively with phosphorus levels in both nutrient rich agricultural wetlands, and negatively with light intensity.