The Ocean Acidification Network

Since the beginning of the industrial revolution, the ocean has absorbed approximately 48% of the anthropogenic CO2 released to the atmosphere, significantly reducing its impact on climate. At current “emissions-avoidance” costs of $10-35 US dollars per ton of CO2 emissions avoided, this represents an ecosystem service worth trillions of dollars. However, this valuable service comes at a steep ecological cost – the acidification of the ocean. As CO2 dissolves in seawater, the pH of the water decreases, making it more acidic. Since the beginning of the industrial revolution, ocean pH has dropped globally by 0.12 pH units. While these pH levels are not alarming in themselves, the rate of change is cause for concern. To the best of our knowledge, the ocean has never experienced such a rapid acidification. By the end of this century, if concentrations of CO2 continue to rise exponentially, we may expect to see changes in pH that are three times greater and 100 times faster than those experienced during the transitions from glacial to interglacial periods. Such large changes in ocean pH have probably not been experienced on the planet for the past 21 million years. How marine ecosystems, coral reefs, and fisheries will respond to this rapid acidification is unknown.
Continue reading ‘The Ocean Acidification Network’

A bill to establish an interagency committee to develop an ocean acidification research

A bill on ocean acidification (S. 1581) has been introduced in the US senate. It seeks to launch a major research initiative in the field of ocean acidification, with a requested funding of 30 millions US$ per year for 2008-2012 and possibly beyond.

The bill can be downloaded, and its legislative path tracked, here.

A geochemical modelling study of the evolution of the chemical composition of seawater linked to a global glaciation: implications for life sustainability

The Snowball Earth theory initially proposed by Kirschvink (Kirschvink, 1992) to explain the Neoproterozoic glacial episodes, suggested that the Earth was fully ice-covered at 720 My (Sturtian episode) and 640 My (Marinoan episode). This succession of extreme climatic crises induced a stress which is considered as a strong selective pressure on the evolution of life (Hoffman et al., 1998). However recent biological records (Corsetti, 2006) do not support this theory as little change is observed in the diversity of microfossils outcrops before and after the Marinoan glacial interval. In this contribution we address this apparent paradox. Using a numerical model of carbon-alkalinity global cycles, we quantify several environmental stresses caused by a global glaciation. We suggest that during global glaciations, the ocean becomes acidic (pH~6), and unsaturated with respect to carbonate minerals. Moreover the quick transition from ice-house to greenhouse conditions implies an abrupt and large shift of the oceanic surface temperature which causes an extended hypoxia. The intense continental weathering, in the aftermath of the glaciation, deeply affects the seawater composition inducing rapid changes in terms of pH and alkalinity. We also propose a new timing for post glacial perturbations and for the cap carbonates deposition, ~2 Myr instead of 200 kyr as suggested in a previous modelling study. In terms of Precambrian life sustainability, seawater pH modifications appear drastic all along the glaciation, but we show that the buffering action of the oceanic crust dissolution processes avoids a total collapse of biological productivity. In opposite short-lived and large post-glacial perturbations are more critical and may have played a role of environmental filter suggested in the classic snowball Earth theory. Only a permissive life (prokaryotes or simple eukaryotes) may explain the relative continuity in microfossils diversity observed before, during and after Neoproterozoic glaciation events.

G. Le Hir, Y. Goddéris, Y. Donnadieu, and G. Ramstein, 2007. A geochemical modelling study of the evolution of the chemical composition of seawater linked to a global glaciation: implications for life sustainability. Biogeosciences Discussions 4:1839-1876. Article.

Exposure to carbon dioxide-rich seawater is stressful for some deep-sea species: an in situ, behavioral study

Since the beginning of the industrial revolution, the concentration of the greenhouse gas carbon dioxide in the atmosphere has increased from 275 to 370 ppm; the increase is thought to have caused much of the rise in global temperature that has occurred during the same period. A means of mitigating its effects is to collect industrial carbon dioxide and sequester it in the deep ocean. Knowledge of effects of such sequestration on deep-sea organisms is crucial to evaluation of the wisdom of deep-ocean sequestration. We therefore tested deep-sea animals for indications that exposure to carbon dioxide-rich seawater is stressful. Our study site was at 3087 m depth off the coast of central California (36°41.91’N, 123°0.14’W). We deployed liquid carbon dioxide in open-topped containers on the sea floor. The carbon dioxide reacted with the carbonate system in the overlying seawater, and carbon dioxide-rich seawater flowed out onto the sediment. We placed inverted-funnel traps near the containers and ~75 m away from them. Measurements of pH confirmed that the area near the containers was exposed to carbon dioxide-rich seawater. As a test taxon, we chose harpacticoid copepods. The traps near the source of the carbon dioxide-rich seawater caught significantly more harpacticoids than those far from it. The harpacticoids apparently attempted to escape from the advancing front of carbon dioxide-rich seawater and therefore presumably found exposure to it to be stressful.
D. Thistle, L. Sedlace, K. R. Carman, J. W. Fleeger, P. G. Brewer, J. P. Barry, 2007. Exposure to carbon dioxide-rich seawater is stressful for some deep-sea species: an in situ, behavioral study. Marine Ecology Progress Series 340:9-16. Article.

Globally increased pelagic carbonate production during the Mid-Brunhes dissolution interval and the CO2 paradox of MIS 11

The Mid-Brunhes dissolution interval (MBDI) represents a period of global carbonate dissolution, lasting several hundred thousand years, centred around Marine Isotope Stage (MIS) 11. Here we report the effects of dissolution in ODP core 982, taken from 1134 m in the North Atlantic. Paradoxically, records of atmospheric CO2 from Antarctic ice-cores reveal no long term trend over the last 400 kyr and suggest that CO2 during MIS 11 was no higher than during the present interglacial. We suggest that a global increase in pelagic carbonate production during this period, possibly related to the proliferation of the Gephyrocapsa coccolithophore, could have altered marine carbonate chemistry in such a way as to drive increased dissolution under the constraints of steady state. An increase in the production of carbonate in surface waters would cause a drawdown of global carbonate saturation and increase dissolution at the seafloor. In order to reconcile the record of atmospheric CO2 variability we suggest that an increase in the flux of organic matter from the surface to deep ocean, associated with either a net increase in primary production or the enhanced ballasting effect provided by an increased flux of CaCO3, could have countered the effect of increased calcification on CO2.

Barker et al., 2006. Globally increased pelagic carbonate production during the Mid-Brunhes dissolution interval and the CO2 paradox of MIS 11. Quaternary Science Reviews 25: 3278-3293. Article.

Carbon emissions causing ocean acidification

An acidic ocean that disintegrates microscopic sea life might sound like “The Horror from the Deep,” the plot of a bad 1950s science fiction movie. It’s a scenario with chilling effects, including the destruction of pteropods, the zooplankton which feed salmon, cod, herring, mackerel and baleen whales.

Along with rising sea levels, warmer temperatures and shrinking glaciers, ocean acidification is another effect of increased carbon dioxide in the earth’s atmosphere. Only recently have scientists begun to study the change in ocean chemistry caused by human-caused carbon emissions.

“This is a very young field,” said Dr. Jeff Short, an environmental chemist and adviser to the Alaska Marine Conservation Council. “It has only been widely appreciated in the last five years.”, Michael Armstrong, 28 March 2007. Article.

Carbon dioxide emissions leading to ocean acidification

Carbon dioxide emissions from human activities are lowering the pH of ocean water leading to ocean acidification. This was a concern shared by Prof Henry Elderfield, University of Cambridge, UK, while speaking at the 41st NIO Foundation Day Lecture – Climate Change: Past, Present, Future – on Tuesday in Dona Paula.

Herald (Goa), 2 January 2007. Article .

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Ocean acidification in the IPCC AR5 WG II

OUP book