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| Titel |
Effects of cyanobacterial-driven pH increases on sediment nutrient fluxes and coupled nitrification-denitrification in a shallow fresh water estuary |
| VerfasserIn |
Y. Gao, J. C. Cornwell, D. K. Stoecker, M. S. Owens |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 7 ; Nr. 9, no. 7 (2012-07-25), S.2697-2710 |
| Datensatznummer |
250007194
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| Publikation (Nr.) |
 copernicus.org/bg-9-2697-2012.pdf |
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| Zusammenfassung |
| 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. |
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