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Thinking of studying earth sciences?
Ocean in a High CO2 World.
8 November 2012
Professor Paul Bown is looking at the fossil records to assess response to ocean acidification. Using a rare find of intact specimens of coccolithophores, micrometre-sized marine plankton fossils, Paul and his colleagues were able to study how the tiny marine organisms cope with rising acidity in the oceans.
Paul and colleague Samantha Gibbs, gave a talk at The Third International Symposium on the Ocean in the High-CO2 World in Monterey, California. They are looking for times in the fossil record when ocean ecosystems experienced similarly dramatic carbon dioxide–driven changes. One popular candidate, known as the Paleocene-Eocene Thermal Maximum (PETM), occurred 55 million years ago during rapid global warming (Science, 18 June 2010, p. 1500).
OCEAN ACIDIFICATION INSIGHTS FROM EXCEPTIONAL COCCOLITHOPHORE FOSSILS
Bown, Paul R., Samantha J. Gibbs, and Jeremy R. Young
Coccolithophores are phytoplanktonic marine calcifiers and an ‘at risk’ group from ocean acidification (OA). Culture and mesocosm experiments provide information on OA effects over short timescales for a small number of taxa. However, coccolithophores are also major components of marine sediments and provide an archive of abundance, diversity and calcification for the last 225 million years. Through study of past environmental change events that incorporate OA we can quantify response over timescales that include acclimatization and adaptation. Results from geological OA events have provided little support for significant extinction or disruption of large-scale calcification, although there are claims of malformation or minor biometric shifts in a handful of taxa. It is possible that OA was not significant at these events, or that coccolithophores were insensitive to the OA change, or that the metrics measured do not provide appropriate description of the response. To extract more information from the geological record we have sought out sediments that provide exceptional preservation of coccolithophores and minimize the biases inherent in fossil records. These sediments preserve intact coccospheres that facilitate direct comparison between modern and fossil cells. They reveal large disparity in cell size and a wide range in calcification types, and allow us to estimate cellular inorganic and organic carbon, variations in cellular/skeletal biometry, and observe intracellular calcification. Preliminary results suggest that some measures of skeletal biometry are sensitive to surface water carbonate chemistry change but we see no unambiguous examples of malformed fossil coccospheres or disruption in growing coccoliths (protococcolith rings).