Abrupt Ocean Acidification Events

Lead Research Organisation: University College London
Department Name: Earth Sciences

Abstract

see lead proposal: Pearson, Cardiff
 
Description Global warming is not the only consequence of rising levels of carbon dioxide in the atmosphere. Because CO2 is an acidic gas, and a high proportion of human emissions get mixed into the ocean, the oceans are becoming more acidic. As humanity aims to limit emissions by setting targets it is vital to predict what effect such acidification will have on marine life and chemical processes in the ocean. We studied the record of several ancient acidification events of different size in order to quantify the response of the oceanic biota, and specifically the phytoplanktonic algal group, the coccolithophores. During this research we found that the evolutionary response in terms of extinctions and origination was muted but that relatively major population shifts occurred, including significant poleward migrations. At a tropical site in Tanzania the abundance of plankton declined significantly during the major Paleocene-Eocene thermal maximum (PETM) climate warming event, and the associated extreme environmental change may have accounted for this temporary exclusion. By looking at global fossil distribution patterns and comparing these with environmental parameters from an Earth system model, we were able to show that the principal control on these species range shifts was temperature, with survival maintained in high-latitude refugia, despite more adverse ocean chemistry conditions. Deleterious effects of ocean acidification were only evidenced when twinned with elevated temperatures. By making use of near-unique exceptional fossil records of complete cell wall covering (coccospheres) and comparing these with modern coccolithophore cells, we were able to interpret how different species responded to the sudden increase in environmental change at the PETM. The species Toweius pertusus continued to reproduce quickly despite the rapidly changing environmental conditions. This would have provided a competitive advantage and is perhaps why closely-related modern-day species considered to be its descendants, such as Emiliana huxleyi, still thrive today. In contrast, the species Coccolithus pelagicus grew more slowly during the period of greatest warmth and this inability to maintain high growth rates may explain why its descendants are less abundant and less widespread in the modern ocean. We were also able to show that the calcification rates of C. pelagicus and T. pertusus declined significantly at this time, due to changes in environmental factors that influenced their growth. An overall reduction in the size of the skeletal components - coccoliths - was seen in T. pertusus, but there was very little evidence for any response to ocean acidification, other than perhaps a slight thinning of C. pelagicus coccoliths.

See also Lead Institution PI - Paul Pearson, Cardiff University
Exploitation Route See Lead Institution PI - Paul Pearson, Cardiff University
Sectors Environment
 
Description Tiny fossils hint at effects of ocean acidification 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Press coverage of talk presented at 3rd International Symposium on the Ocean in a High CO2 World. Exceptional plankton fossils allow comparison of ancient and present responses to changing oceans.

The article led to interest from other researchers.
Year(s) Of Engagement Activity 2012
URL http://www.nature.com/news/tiny-fossils-hint-at-effects-of-ocean-acidification-1.11500