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| Titel |
Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin |
| VerfasserIn |
M. Hagens, C. P. Slomp, F. J. R. Meysman, D. Seitaj, J. Harlay, A. V. Borges, J. J. Middelburg |
| 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 ; 12, no. 5 ; Nr. 12, no. 5 (2015-03-11), S.1561-1583 |
| Datensatznummer |
250117853
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| Publikation (Nr.) |
 copernicus.org/bg-12-1561-2015.pdf |
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| Zusammenfassung |
Coastal areas are impacted by multiple natural and anthropogenic processes
and experience stronger pH fluctuations than the open ocean. These variations
can weaken or intensify the ocean acidification signal induced by increasing
atmospheric pCO2. The development of eutrophication-induced hypoxia
intensifies coastal acidification, since the CO2 produced during
respiration decreases the buffering capacity in any hypoxic bottom water. To
assess the combined ecosystem impacts of acidification and hypoxia, we
quantified the seasonal variation in pH and oxygen dynamics in the water
column of a seasonally stratified coastal basin (Lake Grevelingen, the
Netherlands).
Monthly water-column chemistry measurements were complemented with estimates
of primary production and respiration using O2 light–dark incubations,
in addition to sediment–water fluxes of dissolved inorganic carbon (DIC) and
total alkalinity (TA). The resulting data set was used to set up a proton
budget on a seasonal scale.
Temperature-induced seasonal stratification combined with a high community
respiration was responsible for the depletion of oxygen in the bottom water
in summer. The surface water showed strong seasonal variation in process
rates (primary production, CO2 air–sea exchange), but relatively small
seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In
contrast, the bottom water showed less seasonality in biogeochemical rates
(respiration, sediment–water exchange), but stronger pH fluctuations (0.60
units). This marked difference in pH dynamics could be attributed to a
substantial reduction in the acid–base buffering capacity of the hypoxic
bottom water in the summer period. Our results highlight the importance of
acid–base buffering in the pH dynamics of coastal systems and illustrate the
increasing vulnerability of hypoxic, CO2-rich waters to any acidifying
process. |
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