Actividades relacionadas con el sector pesquero

Denitrification rates were inhibited in all six ponds evaluated. At concentrations of Cl- up to 1000 mg/L, roadside ponds exhibit a tolerance to the increase in salinity. Denitrification rates decreased at different rates in the roadside and forested ponds. While the roadside ponds

exhibited a tolerance to Cl- concentrations up to 1000 mg/L, the rates in forested ponds decreased continuously. Beyond 1000 mg/L Cl-, both sets of ponds demonstrated decreases in

denitrification rates. However, the decrease was not as severe for the roadside ponds. Water chemistry trends were similar for the forested and roadside ponds, with decreasing DOC and pH with Cl- addition. However, the differences in water chemistry between the ponds suggests that

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Cl- is the primary influence on the alteration of N processing. The higher rates in the roadside ponds and higher microbial diversity suggest that the microbial communities have adapted to historical Cl- exposure. However, the decrease in denitrification rate of two orders of magnitude, even for the roadside ponds, suggest that a threshold exists where ecosystem functioning is impacted despite long-term exposure.

The enhanced hydraulic residence time in wetlands allows for N removal through

denitrification which reduces the export of N to coastal ecosystems. However, current research suggests that road salt disrupts the ability of natural ecosystems to mitigate N pollution. Urban environments are impacted by changes in water chemistry and hydrology that inhibit ecosystem functioning. The runoff that is generated from impervious surfaces contains pollutants such as metals, nutrients, and road salt. We rely on our natural and engineered wetland areas to assist in the mitigation of such pollutant loading, particularly for nutrients such as N. Our study suggests that there is a need for additional studies to determine the influence of road salt on N removal in urban settings. Questions remain regarding the ability of microbial communities to adapt to increases in salinity. While previously exposed sediments demonstrated a lower impact, significant decreases in denitrification rates still were observed. Determining the threshold at which microbial communities can no longer function and the timing required for adaptation to occur is essential for setting water quality standards that will ensure adequate N removal and protect coastal ecosystems from the detrimental impacts of excess N loading. Engineering stormwater designs must account for the alteration in rates. Additionally, the impacts of road salt loading to N processing may negatively impact roadside wetland areas, particularly as

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Table 1 Average water quality parameters measured for roadside and forested ponds in

November and January. These concentrations show general trends in water quality between the two sets of ponds and between seasons. All samples were filtered prior to analysis. DOC – dissolved organic carbon; Cl- - chloride; TN – total nitrogen (N); NOx – total nitrate plus nitrite; NH3 – total ammonia species; Org N – organic N (calculated by difference). All concentrations are mg/L. DOC Cl- TN NOx NH3 Org N Roadside November 3.84 4842 0.100 0.006 0.016 0.078 January 3.71 3608 0.249 0.036 0.141 0.073 Forested November 10.71 159 0.263 0.008 0.019 0.236 January 5.8 113 0.153 0.027 0.111 0.014

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Table 2 Correlation matrices for roadside and forested ponds testing the correlation of denitrification rates against the different parameters measured. For denitrification rates, Cl- concentration has the highest correlation

Roadside Cl- pH DOC Denitrification Cl- 1.000 pH -0.853 1.000 DOC -0.654 0.938 1.000 Denitrification -0.937 0.709 0.548 1.000 Forested Cl- pH DOC Denitrification Cl- 1.000 pH -0.798 1.000 DOC -0.624 0.943 1.000 Denitrification -0.921 0.854 0.739 1.000

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