Abstract
Blackbird Creek is the waterway that empties into the Delaware Bay. The lower 21 km of the creek has been shown to have appreciable salinity measurements, suggesting that this portion is influenced by tidal fluctuations. Fourteen sampling stations were established within this lateral range in order to examine the nutrient dynamics of the creek at various points in time. Our objective was to monitor potential changes in water quality conditions, especially on nutrients, in the creek during the day using the low and high tides as the predominating driver for the change. Temperature, pH, dissolved oxygen, conductivity and salinity were monitored bi-weekly at each station. Concentrations of dissolved nitrate (NO3), nitrite (NO2), ammonia (NH3), orthophosphate (PO4), alkalinity (Alk), and turbidity (Tbd) were measured at each station over the course of the field season. Average concentrations were generally low for the nitrogen species: NH4 = 0.11 mgL-1, NO3 = 0.30 mgL-1, NO2 = 0.02 mgL-1. Average alkalinity (92 mgL-1 CaCO3) and turbidity (71 FTU) concentrations were appropriate given the nature of the marsh environment. The average PO4 concentration, however, was elevated (=0.44 mgL-1). The EPA recommends values under 0.1 mgL-1 for this type of waterway. When considered separately, nutrient concentrations on outgoing tides were elevated relative to nutrient concentrations on incoming tides. Overall, the highest concentrations for all parameters occurred at low tide before the shift to the next incoming tide. This suggests that there are greater nutrient concentrations upstream than downstream. Given that land use in the Blackbird Creek watershed is primarily agricultural, it is likely that upstream pore water input from cropland is influencing the nutrient dynamics of the waterway. This information is key to understanding the efficiency of the riparian buffer system that has been established in the watershed and to allow for opportunities for improvement to mitigate nutrient runoff from agricultural fields.
Highlights
Water resources throughout the Mid-Atlantic coastline of the United States are facing constant and increasing threats from growing human population (Postel et al, 1996; Pimentel et al, 2004)
Raw data shows that the mean values for NH3, NO2, PO34−, pH were greater on outgoing tides (Figure 2)
While we monitored differences in majority of water quality parameters (NH3, NO2, PO34−, Turbidity, Salinity, pH, and Conductivity) between incoming and outgoing tides, we found no differences in water quality parameters in relation to land uses in Blackbird Creek
Summary
Water resources throughout the Mid-Atlantic coastline of the United States are facing constant and increasing threats from growing human population (Postel et al, 1996; Pimentel et al, 2004). For example, forested wetlands are drained and used instead for agricultural practices to feed an ever-increasing population, the wetland habitat available for use by aquatic biota is reduced due to altered hydrology, affecting the quality of the water directly. Marsh grasses and forested buffers have been shown to decrease nutrient and pollutant runoff into waterways (Bingham et al, 1980; Castelle et al, 1994; Spruill, 2000). If these buffers are removed, there is a direct line of application of such pollutants from surface water and submarine groundwater discharge into streams and estuaries (Bingham et al, 1980)
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