Nitrogen and Phosphorus Flux Rates from Sediment in the Lower St. Johns River Estuary

Abstract

Internal cycling of nutrients from the sediment and water column can be an important contribution to the total nutrient load of an aquatic ecosystem. Our objective was to estimate the internal nutrient loading of the Lower St. Johns River (LSJR). Dissolved reactive phosphorus (DRP) and ammonium (NH(4)-N) flux from sediments were measured under aerobic and anaerobic water column conditions using intact cores, to estimate the overall contribution of the sediments to P and N loading to the LSJR. The DRP flux under aerobic water column conditions averaged 0.13 mg m(-2) d(-1), approximately 37 times lower than that under anaerobic conditions (4.77 mg m(-2) d(-1)). The average NH(4)-N released from the anaerobic cores (18.03 mg m(-2) d(-1)) was also significantly greater than in the aerobic cores for all sites and seasons, indicating the strong relationship between nutrient fluxes and oxygen availability in the water column. The mean annual internal DRP load was estimated to be 330 metric tons (Mg) yr(-1), 21% of the total P load to the river, while the mean annual internal load of NH(4)-N was determined to be 2066 Mg yr(-1), 28% of the total N load to the LSJR estuary. As water resource managers reduce external loading to the LSJR the frequency of anaerobic events should decline, thereby reducing nutrient fluxes from the sediment to the water column, reducing the internal loading of DRP and NH(4)-N. Results from this study demonstrate that the internal flux of nutrients from sediments may be a significant portion of the total load and should be accounted for in the total nutrient budget of the river for successful restoration.

Benthic mineralization and nutrient exchange over the inner continental shelf of western India

“…4a). A nonlinear decrease in O 2 was also noticed in experiments 2, 3 and 5, similar to observations elsewhere by Sundby et al (1986), Anderson et al (1986), Malecki et al (2004) and Skoog and Arias-Esquivel (2009). These have been attributed to (i) a decrease in the concentration gradient across the benthic boundary layer and (ii) a decrease in the thickness of surficial oxic layer and subsequently a decrease in the number of O 2 -respiring microorganisms .…”

Estimating internal P loading in a deep water reservoir of northern China using three different methods

“…The analysis phosphate diffusion from sediment using Fick's first law were largely used (Malecki et al 2004;Hansen and Márquez-Pacheco 2015;Yin and Kong 2015). Based on the theory of diffusion, diffusive gradients in thin films (DGT) is an in situ accurate measurement to determine the induced flux and concentration of elements in sediment Wu et al 2015).…”

Potential Effects of Sediment Dredging on Internal Phosphorus Loading in a Shallow, Subtropical Lake

“…Internal dissolved P fluxes, measured in 1988 in Lake Okeechobee, were equivalent to external loads (Moore et al 1998, Malecki et al 2004, Fisher et al 2005. Similarly, the significance of the internal P loads in regulating eutrophication has been demonstrated in other shallow lakes (Anderson and Ring 1999, Graneli 1999, Sondergaard et al 1999, Watts 2000, Steinman et al 2004.…”