Trends in Ecology & Evolution
ReviewPaleo-perspectives on ocean acidification
Section snippets
Ocean acidification: the ‘evil twin’ of global warming
One of the major environmental challenges facing society is the impact of increased levels of atmospheric CO2 and other greenhouse gases on the physical and biological systems on earth. These increased levels are mainly due to the combustion of fossil fuels and changes in land use and deforestation. So far, most research has focused on the impacts arising from global warming which has driven (and is continuing to drive) large fundamental changes in biological systems. However, the steady
Evidence of ocean acidification from instrumental time series
The instrumental measurement of pH in seawater has challenged scientists for decades [13]. Recent advances in indicator-based spectrophotometric techniques have allowed the detection of changes in pH arising from the anthropogenic release of CO2 [13], with a few time-series now of sufficient length and quality to record reductions in ocean pH. Examples are those of the North Atlantic Ocean near the Bermuda Islands [14], the subtropical North Pacific Ocean near Hawaii [15], and the northeast
The paleontological context of current and future changes
Current instrumental records of oceanic pH cover only a few decades. However, it is important to go further back in time if we are to fully understand ocean acidification and its impacts. This is essential to understand the context of the changes that we are facing; to unravel impacts and responses of marine biota to previous changes in pH; to test and validate, under past conditions, the physical and biogeochemical models that are used for making future projections; and to investigate if the
Evidence of impacts observed in the field
Field evidence of the impact of ocean acidification on marine organisms has been limited due to the complexity of the measurements of the parameters of the seawater CO2 system and the inherent multifactorial nature of the changes that are occurring as a result of rising levels of atmospheric CO2. Two recent studies have assessed the possible effects on foraminifera, and have observed a recent shell thinning that is probably attributable to ocean acidification. In the first study, shells
Conclusions
The accumulating knowledge of past changes in pH from instrumental time-series and paleo-proxies is providing important contextual information with which to understand the environmental magnitude of the current progressive acidification of the oceans. A decrease in ocean pH is already measurable across several instrumental time-series. Contemporaneous temporal and spatial variability exists in seawater pH. Over the last centuries, reconstructions of seawater pH in coral reefs have also shown a
Acknowledgements
We would like to thank J. Montoya for his suggestion and encouragement to write this review, which was seeded during the 2008 Annual Meeting of the British Ecological Society, and five anonymous reviewers for their critical reading and constructive comments. A. Ridgwell, B. Key, M. Steinacher, N. Bates, J. Dore, D. Etheridge and M. González-Dávila kindly provided data and A. Lana offered invaluable help with the handling of the large datasets needed to produce the map and figures of Box 4.
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