| Description |
The wetlands of Farmington Bay are ecologically and economically important to the surrounding Salt Lake City metropolitan area. This fresh water area is formed by the Jordan River and is thus subject to the river's water quality. Of chief concern in this study are contaminants that contribute to eutrophication such as ammonia, nitrate, and phosphate. The results of how sediments remediate nutrients can be included in previously created wetland health metrics. Determining the factors that control if sediment acts as a sink or a source for ambient water nutrient concentrations could help influence surface water regulation. The sediment nutrient fluxes of nine wetland sites were measured for this study twice over the course of summer, 2014 by comparing the daily changes in nutrient concentrations of water with and without contact to the underlying sediment. These results were then correlated to biogeochemical parameters such as dissolved oxygen content, organic carbon availability, and size of bacterial community in the sediment for each site to explain which factors controlled sediment nutrient fluxes Overall, in ambient conditions, most sites displayed sediment as an ammonia source during the daytime as decomposition likely outpaced nitrification. The sediment was also a sink for phosphate while nitrate trends varied between sites. After spiking the experimental chambers with nutrients to witness nutrient pulses, the nitrogen-cycling biological mechanisms were accelerated, while the sediment failed to absorb the extra phosphate. All but one site's sediment fluxes were statistically comparable via Z test, and the remaining eight were used to conduct a principal component analysis to identify important variables. Ammonia sediment fluxes were found to be controlled by nitrifying bacteria and from the concentration gradient between the pore water and ambient water. Nitrate sediment flux correlated with the amount of denitrifying bacteria present in the sediment, the total solid organic carbon, and daily changes in temperature. Last, phosphate fluxes were influenced by diurnal cycling of the phosphate attached to iron in the sediment and changes in the dissolved oxygen saturation of the water column. |
