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| Titel |
Benthic dissolved inorganic carbon dynamics in the Gulf of Biscay (June 2006, May 2007 and May 2008 |
| VerfasserIn |
K. Suykens, B. Delille, A. V. Borges |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026008
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| Zusammenfassung |
| The biogeochemical properties of an extensive bloom of the coccolithophore, Emiliania
huxleyi, at the shelf break in the northern Gulf of Biscay was investigated in June 2006, May
2007 and May 2008. We report the results from the benthic measurements during the three
cruises. Benthic respiration rates were quite low and varied between 2 and 9 mmol m-2
d-1, in agreement with the fact that the study area consists of sandy sediments
with low organic matter content. Benthic respiration was well correlated to the
Chlorophyll-a (Chl-a) content of the top 1 cm of the sediment, and to the grain size fraction
smaller than 63 μm, indicating the influence of turbidity to the deposition of fresh
material. Chl-a values in May 2007 and 2008 were higher than in June 2006 in
agreement with the fact that the 2007 and 2008 cruises were conducted after the first
large peak of phytoplankton biomass associated to diatoms, visible on the Seawifs
Chl-a values in the study area, and that the 2006 cruise took place after the second
smaller peak associated to coccolithophores. 210Pbxs profiles (of the 2007 and 2008
stations) indicate that the sediments are well mixed and steadily accumulated below
the mixed layer (up to 10 cm depth in the sediments). 234Thxs activities show a
deposition of fresh material in the upper 2 cm of the sediments at almost all stations
(2007 and 2008). A negative relation between 234Thxs and Chl-a remains to be
investigated but could relate to rapid resuspension zones, a delay in bloom arrival of
detritus to the surface sediments or increased remineralization through aerobic and
anaerobic pathways based on high bioturbation rates. Based on the co-variance of
water-sediment TA fluxes and O2 consumption, evidence was found for dissolution of
CaCO3 due to acidification of superficial sediments in relation to the production of
CO2 by respiration, as shown by the positive correlation between the dissolved
inorganic carbon (DIC) flux and respiration. There was an increase in nitrate in the
overlying water of the sediment cores, ranging from 0.03 to 1.2 mmol m-2 d-1over an
average incubation period of 42 hours, however some stations give evidence of
denitrification. There is an increase in silicate at all stations of 0.05 to 1.0 mmol m-2 d-1. |
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