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| Titel |
Photosynthetic production in the central Arctic Ocean during the record sea-ice minimum in 2012 |
| VerfasserIn |
M. Fernández-Méndez, C. Katlein, B. Rabe, M. Nicolaus, I. Peeken, K. Bakker, H. Flores, A. Boetius  |
| 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. 11 ; Nr. 12, no. 11 (2015-06-09), S.3525-3549 |
| Datensatznummer |
250117976
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| Publikation (Nr.) |
 copernicus.org/bg-12-3525-2015.pdf |
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| Zusammenfassung |
| The ice-covered central Arctic Ocean is characterized by low primary
productivity due to light and nutrient limitations. The recent reduction in
ice cover has the potential to substantially increase phytoplankton primary
production, but little is yet known about the fate of the ice-associated
primary production and of the nutrient supply with increasing warming. This
study presents results from the central Arctic Ocean collected during summer
2012, when sea-ice extent reached its lowest ever recorded since the onset of satellite
observations. Net primary productivity (NPP) was measured in the water
column, sea ice and melt ponds by 14CO2 uptake at different
irradiances. Photosynthesis vs. irradiance (PI) curves were established in
laboratory experiments and used to upscale measured NPP to the deep Eurasian
Basin (north of 78° N) using the irradiance-based Central Arctic
Ocean Primary Productivity (CAOPP) model. In addition, new annual production
has been calculated from the seasonal nutrient drawdown in the mixed layer since
last winter. Results show that ice algae can contribute up to 60% to
primary production in the central Arctic Ocean at the end of the productive
season (August–September). The ice-covered water column has lower NPP rates
than open water due to light limitation in late summer. As indicated by the
nutrient ratios in the euphotic zone, nitrate was limiting primary
production in the deep Eurasian Basin close to the Laptev Sea area, while
silicate was the main limiting nutrient at the ice margin near the Atlantic
inflow. Although sea-ice cover was substantially reduced in 2012, total
annual new production in the Eurasian Basin was 17 ± 7 Tg C yr−1,
which is within the range of estimates of previous years. However, when
adding the contribution by sub-ice algae, the annual production for the deep
Eurasian Basin (north of 78° N) could double previous estimates
for that area with a surplus of 16 Tg C yr−1. Our data suggest that
sub-ice algae are an important component of the productivity in the
ice-covered Eurasian Basin of the central Arctic Ocean. It remains an
important question whether their contribution to productivity is on the rise with
thinning ice, or whether it will decline due to overall sea-ice retreat and be
replaced by phytoplankton. |
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