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| Titel |
Macroalgae contribute to nested mosaics of pH variability in a subarctic fjord |
| VerfasserIn |
D. Krause-Jensen, C. M. Duarte, I. E. Hendriks, L. Meire, M. E. Blicher, N. Marbá, M. K. Sejr |
| 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. 16 ; Nr. 12, no. 16 (2015-08-19), S.4895-4911 |
| Datensatznummer |
250118065
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| Publikation (Nr.) |
 copernicus.org/bg-12-4895-2015.pdf |
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| Zusammenfassung |
| The Arctic Ocean is considered the most vulnerable ecosystem to ocean
acidification, and large-scale assessments of pH and the saturation state for
aragonite (Ωarag) have led to the notion that the Arctic Ocean
is already close to a corrosive state. In high-latitude coastal waters the
regulation of pH and Ωarag is, however, far more complex than
offshore because increased biological activity and input of glacial meltwater
affect pH. Effects of ocean acidification on calcifiers and non-calcifying
phototrophs occupying coastal habitats cannot be derived from extrapolation
of current and forecasted offshore conditions, but they
require an understanding of the regimes
of pH and Ωarag in their coastal habitats. To increase
knowledge of the natural variability in pH in the Arctic coastal zone and
specifically to test the influence of benthic vegetated habitats, we
quantified pH variability in a Greenland fjord in a nested-scale approach. A
sensor array logging pH, O2, PAR, temperature and salinity was applied
on spatial scales ranging from kilometre scale across the horizontal
extension of the fjord; to 100 m scale vertically in the fjord, 10–100 m
scale between subtidal habitats with and without kelp forests and between
vegetated tidal pools and adjacent vegetated shores; and to centimetre to
metre scale within kelp forests and millimetre scale across diffusive
boundary layers of macrophyte tissue. In addition, we assessed the temporal
variability in pH on diurnal and seasonal scales. Based on pH measurements
combined with point samples of total alkalinity, dissolved inorganic carbon
and relationships to salinity, we also estimated variability in Ωarag. Results show variability in pH and Ωarag of up
to 0.2–0.3 units at several scales, i.e. along the horizontal and vertical
extension of the fjord, between seasons and on a diel basis in benthic
habitats and within 1 m3 of kelp forest. Vegetated intertidal pools
exhibited extreme diel pH variability of > 1.5 units and macrophyte
diffusive boundary layers a pH range of up to 0.8 units. Overall, pelagic and
benthic metabolism was an important driver of pH and Ωarag
producing mosaics of variability from
low levels in the dark to peak levels at high irradiance generally appearing
favourable for calcification. We suggest that productive coastal environments
may form niches of high pH in a future acidified Arctic Ocean. |
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