Nitrogen and Phosphorus Attenuation within the Stream Network of a Coastal, Agricultural Watershed

Abstract

Streams alter the concentration of nutrients they transport and thereby influence nutrient loading to estuaries downstream; however, the relationship between in-stream uptake, discharge variability, and subsequent nutrient export is poorly understood. In this study, instream N and P uptake were examined in the stream network draining a row-crop agricultural operation in coastal North Carolina. The effect of in-stream nutrient uptake on estuarine loading was examined using continuous measurements of watershed nutrient export. Remineralization from the streambed (vs. terrestrial sources) was the apparent source of NH 4 1 and PO 4 32 to the estuary during base flow.In-stream uptake reduced the dissolved inorganic N to dissolved inorganic P ratio of water exported to the N-limited estuary, thus limiting the potential for estuarine phytoplankton growth.

Modelling catchment management impact on in-stream phosphorus loads in northern Victoria

“…In-stream attenuation of phosphorus due to either biotic or abiotic mechanisms of uptake and removal was simulated as a firstorder, exponential decay along the stream (Simmons and Cheng, 1985;Ensign et al, 2006), and calculated as a function of stream length (L SUB , in m) and reach mean annual flow (Q MAF,SUB , Ml y À1 ):…”

Combined inverse modeling approach and load duration curve method for variable nitrogen total maximum daily load development in an agricultural watershed

“…An experimental method similar to the method proposed by Ensign et al (2006) and Gibson and Meyer (2007) was adopted to measure the in-stream first-order TN loss rate (K) in the ChangLe River system monthly from January 2004 to December 2008. Four 0.3-km segments were selected in the mainstream and three tributaries (Fig.…”

Watershed-Scale Tradeoffs in Water Quantity and Quality Attributes for Conservation Policy

“…Biogeochemicals, such as heavy metals, nutrients, and sediment, change in concentration depending on loading rates from different land uses, such as urban, agricultural, forest, wetlands, and riparian zones, and movement in the water column. While there are biophysical studies that evaluate tradeoffs among water quality attributes in watersheds (Puckett and Hughes 2005;Miller et al 2003;Calhoun et al 2002;Randall and Mulla 2000;Andraski and Bundy 2002;Hayakawa et al 2006;Ensign et al 2005), more studies are needed on the implications for policy of the incorporation of tradeoff information . Puckett and Hughes (2005) investigated the transport and fate of nitrate and pesticides in different flow regimes in a shallow aquifer and an adjacent stream in South Carolina.…”

“…As well, the systems that had the lowest levels of nitrogen in runoff had the highest reduction in phosphorus levels. Ensign et al (2005) studied nitrogen and phosphorus attenuation within a stream network of an agricultural watershed in coastal North Carolina. They investigated the effect of instream nutrient uptake on estuarine loading using continuous measurements of watershed nutrient export.…”