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| Titel |
Pteropods under the impact of ocean acidification and warming: a novel approach of calcification rate measurements in pre-winter Limacina helicina and effects on overwintering L. helicina and L. retroversa |
| VerfasserIn |
Jan Büdenbender, Silke Lischka, Kai G. Schulz, Ulf Riebesell |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056529
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| Zusammenfassung |
| The increase in atmospheric CO2 concentrations caused by anthropogenic activities could
lead to aragonite (polymorph of calcium carbonate) sub-saturation in parts of the Arctic
surface ocean by 2020 if emissions follow business as usual scenarios. Most pronounced
effects are expected to take place during winter-time. Sub-saturated water was shown to
negatively impact a variety of marine calcifying organisms. The polar calcifying
pteropod Limacina helicina can contribute up to 20% of the Arctic zooplankton
biomass at times and has a key function in the Arctic epipelagic food web. The
temperate-boreal sibling species L. retroversa is frequently introduced to Arctic regions with
Atlantic water masses. Both species contribute significantly to vertical carbon flux. In
September/October 2009 and in January/February 2010 incubation experiments
were carried out in Ny Ålesund/Svalbard at three temperatures (3, 5 and 8Ë C) and
four pCO2 levels (180, 400, 750 and 1150 ppm) with durations of 29 and 9 days,
respectively. In the 2009 experiment we used a novel approach of a 13C stable isotope
incubation for measuring pteropod calcification rates. First results show that 13C
concentrations varied in the total particulate carbon (TPC) of the organism but stayed
constant in the particulate organic carbon (POC). From mass-balance calculations the
variation in the TP13C concentrations result from 13C concentration changes of
the particulate inorganic carbon (PIC) and/or changing PIC/POC ratios. The first
is most likely affected by different calcification rates whereas the second could
be additionally affected by changing respiration rates in response to the applied
treatments. Our results show trends of 13C enrichment in organisms with increasing
temperature and with decreasing pCO2 levels, suggesting a positive temperature and a
negative CO2 effect on pteropod calcification rates. To investigate species-specific
differences, in winter 2010 (January/February) temperature and CO2 perturbation
experiments were carried out with Limacina helicina and L. retroversa both occurring in
Kongsfjord/Svalbard. Preliminary results reveal growth cessation in winter (with respect to
absolute shell size) of both, Limacina helicina and L. retroversa. However, the Atlantic-type
L. retroversa seemed to be more sensitive to high pCO2 conditions with respect
to mortality and shell degradation as compared to its polar relative L. helicina. |
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