 |
| Titel |
Surface 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
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025944
|
|
|
|
|
|
| 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 surface measurements during all cruises.
Seawifs Chlorophyll-a (Chl-a) values in the study area indicate that seasonal cycles of
phytoplankton biomass were remarkably similar in 2006, 2007 and 2008 with a first peak
in mid-April associated to diatoms and a second peak in late May associated to
coccolithophorids. During both cruises, Total Alkalinity (TA) values showed strong
non-conservative behavior, indicative of the impact of calcification. TA anomalies were
positively related to the degree of stratification, in agreement with the ecophysiology of
coccolithophores, whereby these organisms flourish in nutrient depleted and high light
availability conditions. The largest TA anomalies were observed in the high reflectance
coccolith patch where we also observed an increase in the partial pressure of CO2 normalized
at a constant temperature of 13Ë C (pCO2@13Ë C), in agreement with the transfer of
CO2 from the bicarbonate pool during calcification. TA anomalies were of similar
amplitude during both cruises, indicating that calcification affected markedly the
dissolved inorganic carbon dynamics. During both cruises, pCO2 values ranged
form 250 to 375 μatm and the area was found to act as a sink for atmospheric CO2.
pCO2@13Ë C in the water column was negatively related to TA anomalies in agreement
with an overall production of CO2 related to calcification. Hence, the calcifying
phase of the E.huxleyi bloom decreased the sink of atmospheric pCO2, but did
not reverse the direction of the flux. pCO2@13Ë C values in June 2006 lie below
the values in May 2007, due to the cumulated impact of primary production on
pCO2, since the 2006 cruise was carried out later in the year than the 2007 cruise. |
|
|
|
|
|
|