Effects of cyanobacterial-driven pH increases on sediment nutrient fluxes and coupled nitrification-denitrification in a shallow fresh water estuary

Abstract

<jats:p>Abstract. Summer cyanobacterial blooms caused an elevation in pH (9 to ~10.5) that lasted for weeks in the shallow and tidal-fresh region of the Sassafras River, a tributary of Chesapeake Bay (USA). Elevated pH promoted desorption of sedimentary inorganic phosphorus and facilitated conversion of ammonium (NH4+) to ammonia (NH3). In this study, we investigated pH effects on exchangeable NH4+ desorption, pore water diffusion and the flux rates of NH4+, soluble reactive phosphorus (SRP) and nitrate (NO3−), nitrification, denitrification, and oxygen consumption. Elevated pH enhanced desorption of exchangeable NH4+ through NH3 formation from both pore water and adsorbed NH4+ pools. Progressive penetration of high pH from the overlying water into sediment promoted the mobility of SRP and the release of total ammonium (NH4+ and NH3) into the pore water. At elevated pH levels, high sediment-water effluxes of SRP and total ammonium were associated with reduction of nitrification, denitrification and oxygen consumption rates. Alkaline pH and the toxicity of NH3 may inhibit nitrification in the thin aerobic zone, simultaneously constraining coupled nitrification–denitrification with limited NO3− supply and high pH penetration into the anaerobic zone. Geochemical feedbacks to pH elevation, such as enhancement of dissolved nutrient effluxes and reduction in N2 loss via denitrification, may enhance the persistence of cyanobacterial blooms in shallow water ecosystems.</jats:p>

Multivariate benthic ecosystem functioning in the Arctic – benthic fluxes explained by environmental parameters in the southeastern Beaufort Sea

“…The faunal composition, which has important effects on ammonium release by sediment oxygenation and bioturbation, might be one of these lacking measurements (Braeckman et al, 2010;Laverock et al, 2011;Piot et al, 2013). But also environmental parameters of long-term variability, such as pore water pH or sediment mineralogy are assumed to influence ammonium fluxes in the sediments (Gao et al, 2012;Müller, 1977). Such data is unavailable for our study, but including pore water pH in statistical models in the future may yield higher explicative power for ammonium fluxes.…”

The Effects of the Toxic Cyanobacterium Limnothrix (Strain AC0243) on Bufo marinus Larvae

“…Treatment flasks showed higher pH concentrations than the control flasks (Table 1). Previous research has shown that growth of cyanobacteria in high concentrations may cause an increase in the pH [45]. Drops in pH (pH < 6) have been shown to cause mortalities in anuran larvae either directly, by having a toxic effect on biota or indirectly, by causing an increase in toxicity of other chemicals or metals [46,47].…”

Authigenic apatite and octacalcium phosphate formation due to adsorption–precipitation switching across estuarine salinity gradients

“…Decreasing Eh in sediment from upper to lower zones involve critical levels for reduction of ferric iron compounds (e.g. Gotoh and Patrick, 1974). These critical levels facilitate desorption of Fe-(hydr)oxide-bound P due to less efficient sorption of P by iron in the Fe(II) state compared to the Fe(III) state (Hartzell and Jordan, 2012;Sundareshwar and Morris, 1999).…”

“…In contrast, detrital fluorapatite (FAP) is unlikely to dissolve in seawater (Ruttenberg, 1990;Howarth et al, 1995). In addition to the dependence on species-specific saturation states (Atlas, 1975;Gunnars et al, 2004), the occurrence of Ca-P minerals depends on their formation kinetics (Atlas and Pytkowicz, 1977;Gulbrandsen et al, 1984;Gunnars et al, 2004;Jahnke et al, 1983;Sheldon, 1981) and inhibitors such as Mg 2+ ions (Golubev et al, 1999;Gunnars et al, 2004;Martens and Harriss, 1970). In general, the first solid to form is the one which is thermodynamically least favoured (Ostwald step rule; see Morse andCasey, 1988 andNancollas et al, 1989).…”