Intertidal coastal sediments are important centers for nutrient transformation, regeneration, and storage. Sediment resuspension, due to wave action or tidal currents, can induce nutrient release to the water column and fuel primary production. Storms and extreme weather events are expected to increase due to climate change in coastal areas, but little is known about their effect on nutrient release from coastal sediments. We have conducted in-situ sediment resuspension experiments, in which erosion was simulated by a stepwise increase in current velocities, while measuring nutrient uptake or release in field flumes positioned on intertidal areas of a tidal bay (Eastern Scheldt) and an estuary (Western Scheldt). In both systems, the water column concentration of ammonium (NH4+) and nitrite (NO2−) increased predictably with greater erosion as estimated from pore water dilution and erosion depth. In contrast, the phosphate (PO43−) dynamics were different between systems, and those of nitrate (NO3−) were small and variable. Notably, sediment resuspension caused a decrease in the overlying water PO43− concentration in the tidal bay, while an increase was observed in the estuarine sediments. Our observations showed that the concentration of PO43− in the water column was more intensely affected by resuspension than that of NH4+ and NO2−. The present study highlights the differential effect of sediment resuspension on nutrient exchange in two contrasting tidal coastal environments.
<p>Coastal areas are subjected to several anthropogenic stressors with much of the world&#8217;s intertidal areas receding due to human activities, coastal erosion, and sea level rise. The Eastern Scheldt (ES) tidal bay in The Netherlands is predicted to lose around 35 % of intertidal areas by 2060. Our study investigated differences between biogeochemical fluxes of intertidal and subtidal sediments of the ES and assessed how ongoing intertidal loss may modify the sedimentary ecosystem functioning of this tidal bay in the coming decades. Monthly fluxes and porewater concentrations of dissolved inorganic nitrogen (DIN), phosphorous (DIP), silica, carbon and oxygen (O<sub>2</sub>) as well as organic matter characteristics were measured from intertidal and subtidal sediments from June 2016 &#8211; December 2017. O<sub>2</sub> fluxes were 37% higher in the intertidal, and these sediments exhibited influxes of nitrates (-1.2 mmol m<sup>-2</sup> d<sup>-1</sup>) and DIP (-0.03 mmol m<sup>-2</sup> d<sup>-1</sup>). In contrast, subtidal sediments exhibited an average efflux of nitrates (0.28 mmol m<sup>-2</sup> d<sup>-1</sup>) and DIP (0.09 mmol m<sup>-2</sup> d<sup>-1</sup>). Intertidal areas removal of DIN and DIP was 34 % and 38% higher than in the subtidal suggesting stronger denitrification and phosphorus adsorption to solid particles. The potential loss of biogeochemical functionality due to intertidal area loss by 2060 was estimated. In the next 40 years, the ES tidal bay may experience a reduction of 11 % and 8 % for respective nitrogen and phosphorus removal. Given the global observations of eroding intertidal areas and rising sea levels, we suggest that the predicted habitat loss may cause significant changes for coastal biogeochemistry and should be investigated further to understand its potential consequences for coastal ecosystems.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.