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| Titel |
Effect of elevated CO2 on organic matter pools and fluxes in a summer Baltic Sea plankton community |
| VerfasserIn |
A. J. Paul, L. T. Bach, K.-G. Schulz, T. Boxhammer, J. Czerny, E. P. Achterberg, D. Hellemann, Y. Trense, M. Nausch, M. Sswat, U. Riebesell |
| 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. 20 ; Nr. 12, no. 20 (2015-10-28), S.6181-6203 |
| Datensatznummer |
250118144
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| Publikation (Nr.) |
 copernicus.org/bg-12-6181-2015.pdf |
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| Zusammenfassung |
| Ocean acidification is expected to influence plankton community structure and
biogeochemical element cycles. To date, the response of plankton communities
to elevated CO2 has been studied primarily during nutrient-stimulated blooms.
In this CO2 manipulation study, we used large-volume
(~ 55 m3) pelagic in situ mesocosms to enclose a natural summer,
post-spring-bloom plankton assemblage in the Baltic Sea to investigate the
response of organic matter pools to ocean acidification. The carbonate system
in the six mesocosms was manipulated to yield average fCO2 ranging
between 365 and ~ 1230 μatm with no adjustment of naturally
available nutrient concentrations. Plankton community development and key
biogeochemical element pools were subsequently followed in this
nitrogen-limited ecosystem over a period of 7 weeks. We observed higher
sustained chlorophyll a and particulate matter concentrations
(~ 25 % higher) and lower inorganic phosphate concentrations in the
water column in the highest fCO2 treatment (1231 μatm)
during the final 2 weeks of the study period (Phase III), when there was
low net change in particulate and dissolved matter pools. Size-fractionated
phytoplankton pigment analyses indicated that these differences were driven
by picophytoplankton (< 2 μm) and were already established
early in the experiment during an initial warm and more productive period
with overall elevated chlorophyll a and particulate matter concentrations.
However, the influence of picophytoplankton on bulk organic matter pools was
masked by high biomass of larger plankton until Phase III, when the
contribution of the small size fraction (< 2 μm) increased to
up to 90 % of chlorophyll a. In this phase, a CO2-driven increase in
water column particulate carbon did not lead to enhanced sinking material
flux but was instead reflected in increased dissolved organic carbon
concentrations. Hence ocean acidification may induce changes in organic
matter partitioning in the upper water column during the low-nitrogen summer
period in the Baltic Sea. |
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