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| Titel |
Direct observations of diel biological CO2 fixation on the Scotian Shelf, northwestern Atlantic Ocean |
| VerfasserIn |
H. Thomas, S. E. Craig, B. J. W. Greenan, W. Burt, G. J. Herndl, S. Higginson, L. Salt, E. H. Shadwick, J. Urrego-Blanco |
| 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. 6 ; Nr. 9, no. 6 (2012-06-27), S.2301-2309 |
| Datensatznummer |
250007132
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| Publikation (Nr.) |
 copernicus.org/bg-9-2301-2012.pdf |
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| Zusammenfassung |
| Much of the variability in the surface ocean's carbon cycle can be
attributed to the availability of sunlight, triggering surface heat flux and
photosynthesis, which in turn regulate the biogeochemical cycling of carbon
over a wide range of time scales. The critical processes of this carbon
cycle regulation, occurring at time scales of a day or less, however, have
undergone few investigations, most of which have been limited to time spans
of several days to months. Optical methods have helped to infer short-term
biological variability, but complementing investigations of the oceanic
CO2 system are lacking. We employ high-frequency
CO2 and optical observations covering the full seasonal cycle
on the Scotian Shelf, northwestern Atlantic Ocean, in order to unravel diel
periodicity of the surface ocean carbon cycle and its effects on annual
budgets. Significant diel periodicity in the surface CO2
system occurs only if the water column is sufficiently stable as observed
during seasonal warming. During that time biological CO2
drawdown, or net community production (NCP), is delayed for several hours
relative to the onset of photosynthetically available radiation (PAR), due
to diel cycles in chlorophyll a concentration and
to grazing. In summer, NCP decreases by more than 90%, coinciding with
the seasonal minimum of the mixed layer depth and resulting in the
disappearance of the diel CO2 periodicity in the surface
waters. |
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