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| Titel |
Is coccolithophore distribution in the Mediterranean Sea related to seawater carbonate chemistry? |
| VerfasserIn |
A. Oviedo, P. Ziveri, M. Álvarez, T. Tanhua |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 11, no. 1 ; Nr. 11, no. 1 (2015-01-09), S.13-32 |
| Datensatznummer |
250117123
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| Publikation (Nr.) |
 copernicus.org/os-11-13-2015.pdf |
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| Zusammenfassung |
| The Mediterranean Sea is considered a "hot spot" for climate change, being
characterized by oligotrophic to ultra-oligotrophic waters and rapidly increasing seasurface temperature and
changing carbonate chemistry. Coccolithophores are considered a dominant
phytoplankton group in these waters. As marine calcifying organisms they are
expected to respond to the ongoing changes in seawater carbonate chemistry.
We provide here a description of the
springtime coccolithophore distribution in the Mediterranean Sea and relate
this to a broad set of in situ-measured environmental variables. Samples were taken
during the R/V Meteor (M84/3) oceanographic cruise in April 2011, between 0 and 100 m water
depth from 28 stations. Total diatom and silicoflagellate cell
concentrations are also presented. Our results highlight the importance of
seawater carbonate chemistry, especially [CO32−] but also
[PO43−] in unraveling the distribution of heterococcolithophores,
the most abundant coccolithophore life phase. Holo- and
heterococcolithophores respond differently to environmental factors. For
instance, changes in heterococcolithophore assemblages were best linked to
the combination of [CO32−], pH, and salinity (ρ = 0.57),
although salinity might be not functionally related to coccolithophore
assemblage distribution. Holococcolithophores, on the other hand, showed
higher abundances and species diversity in oligotrophic areas (best fit,
ρ = 0.32 for nutrients), thriving in nutrient-depleted waters.
Clustering of heterococcolithophores revealed three groups of species
sharing more than 65% similarities. These clusters could be assigned to
the eastern and western basins and deeper layers (below 50 m),
respectively. In addition, the species Gephyrocapsa oceanica, G. muellerae,
and Emiliania huxleyi morphotype B/C are spatially
distributed together and trace the influx of Atlantic waters into the
Mediterranean Sea. The results of the present work emphasize the importance
of considering holo- and heterococcolithophores separately when analyzing
changes in species assemblages and diversity. Our findings suggest that
coccolithophores are a main phytoplankton group in the entire Mediterranean
Sea and can dominate over siliceous phytoplankton. They have life stages
that are expected to respond differently to the variability in seawater
carbonate chemistry and nutrient concentrations. |
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