Nitrogen release from surface sand of a high energy beach along the southeastern coast of North Carolina, USA

Abstract

This study examined changes in dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) in coastal seawater after exposure to sand along a high energy beach face over an annual cycle between April 2004 and July 2005. Dissolved organic nitrogen, NO 3 -, and NH 4 + were released from sand to seawater in laboratory incubation experiments clearly demonstrating that they are a potential source of N to underlying groundwater or coastal seawater. DON increases in seawater, after exposure to surface sands in laboratory experiments, were positively correlated with in situ water column DON concentrations measured at the same time as sand collection. Increase in NO 3 -and NH 4 + were not correlated with their in situ concentrations. This suggests that DON released from beach sands is relatively more recalcitrant while NO 3 -and NH 4 + are utilized rapidly in the coastal ocean. The release of N was seasonal with carbon to nitrogen ratios indicating that recent primary productivity was responsible for the largest fluxes in summer while more degraded humic material contributed to lower fluxes in winter. Fluxes of total dissolved nitrogen (DON and DIN) from surface sand (2.1 9 10 -4 mol m -2 h -1 ) were similar to that of groundwater and more than an order of magnitude larger than rain deposition indicating the potential importance of surface sand derived nitrogen to the coastal zone with a corresponding impact on primary productivity.

Factors affecting surf zone phytoplankton production in Southeastern North Carolina, USA

“…The significant, positive effects of 1-day rainfall on PP and PB suggest that rainwater may pump pore water through the highly permeable beach and thereby enhance nutrient fluxes into the nearshore zone. Our observations of pore water nutrients (Table 2b) and other studies of beach nutrient dynamics (Campbell andBate, 1996, 1997;Avery et al, 2008) support this inference. Questions remain about the magnitude of this effect vs. other nutrient supply mechanisms, such as estuarine outwelling and in situ regeneration, but the rainfall effects suggest the overall importance of nutrient supply in regulating surf zone production.…”

Benthic Microalgal Biomass on Ocean Beaches: Effects of Sediment Grain Size and Beach Renourishment

“…One caution must be considered, however, in that low biomass in such high-energy, high-light environments does not necessarily equate to low production. Ocean beaches may experience relatively high nutrient flux rates (Avery et al, 2008) that, coupled with high light levels, might drive high production that is masked by high grazing and/or high physical removal rates, so we do not interpret low biomass as evidence that benthic microalgae on beaches are unproductive. Lack of such productivity data in the literature likely arises from the extreme challenges of measuring benthic microalgal production in such a physically dynamic environment.…”

Carbon dynamics driven by seawater recirculation and groundwater discharge along a forest-dune-beach continuum of a high-energy meso-macro-tidal sandy coast

“…It would have been overestimated by 8000 tons per year if active CO2 degassing between the forest soil aquifer and the supratidal beach had been neglected. High-energy sandy beaches are recognized as environments in which organic matter mineralization and recycling of the associated nutrients are very active (Avery et al, 2008;Rauch et al, 2008;Rocha, 2008;Anschutz et al, 2009;Dugan et al, 2011;Charbonnier et al, 2013). Previous studies at the Truc Vert Beach revealed that oxygen consumption through aerobic respiration takes place in the intertidal recirculation cell (Anschutz et al, 2009;Charbonnier et al, 2013).…”