Responses of coccolithophores to ocean acidification: a meta-analysis
As a consequence of anthropogenic carbon emissions the surface ocean gradually takes up vast amounts of C02. Elevated carbon dioxide concentrations in seawater modify the carbonate system and decrease the pH, a process called ocean acidification. Accumulating evidence suggests that calcifying organi...
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| Format: | Thesis |
| Language: | English |
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2012
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| Online Access: | https://oceanrep.geomar.de/id/eprint/20165/ https://oceanrep.geomar.de/id/eprint/20165/1/Dipl.%202012%20Meyer,%20J.pdf |
| Summary: | As a consequence of anthropogenic carbon emissions the surface ocean gradually takes up vast amounts of C02. Elevated carbon dioxide concentrations in seawater modify the carbonate system and decrease the pH, a process called ocean acidification. Accumulating evidence suggests that calcifying organisms such as coccolithophores are most vulnerable to ocean acidification. As those single-celled algae are important primary producers and responsible for a large part of calcium carbonate production in the sea, a variation in their physiological responses to ocean acidification would impact the ecosystem as weil as the carbonate cycles of the ocean. In the past, a variety of studies examined the biological responses of coccolithophores in carbonate chemistry manipulation experiments. However, variable and partly inconsistent results have been gained in those experiments. In the present study the existing data have been synthesized in order to quantify the responses of coccolithophores to ocean acidification with the help of a meta-analysis. Thus, it was possible to make a prediction of the true effect size of their responses to increased pC02 concentrations. Despite some intra-specific variability, a general negative effect of ocean acidification on calcification as weil as an the cellular PIC/POC ratio was observed for the most abundant species Emi/iania huxleyi and Gephyrocapsa oceanica, whereas the more heavily calcified species Cocco/ithus braarudii did not show any response to increased pC02 concentrations. Photosynthesis in Gephyrocapsa oceanica was positively affected, while no effect was observed for the other coccolithophore species. There was no evidence that the carbonate chemistry perturbation method was responsible for the inconsistent results regarding calcification and PIC/POC ratio in the single experiments. However, it remains to be clarified whether the perturbation method affects photosynthesis rates in coccolithophores, as responses varied significantly between total alkalinity (TA) and dissolved ... |
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