Acidification and other global issues

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Ocean acidification is a new and looming threat that could undermine the marine food web, and preclude the coral development upon which much sustainable tourism depends. The dissolution of carbon dioxide (CO2) in seawater leads to considerable acidification and changes to the geobiochemical carbonate balance. The oceans have absorbed one third of anthropogenic CO2 emissions, which has caused significant acidification. These emissions affect the marine environment directly, in addition to any other impacts that occur due to climate change. The continuation of current trends will lead to a level of acidification without precedent for several million years, and that will last for millennium. The effects on marine ecosystems cannot be forecast exactly. There is the risk of profound changes to the food web, as calcification of marine organisms may be precluded, or in some cases prevented.

Acidification, as well as sea level rise, will remain for the next few thousand years. Sea level rise is one factor in water impacts and erosion, and is generally understood as a slower but predictable impact of climate change. Over time, sea level rise may change coastal, island and marine ecosystems, particularly if tourist development and transportation infrastructure prevents these ecosystems from moving inland. In addition, sea level rise will affect fresh water systems. One fresh water impact is increasing salt water intrusion in aquifers and estuaries, particularly depleted aquifers or subsiding estuaries.

Another emerging issues is the impact of high sea surface temperatures on the intensity of tropical cyclones and hurricanes. There is also an increasing understanding of the role of oceans as a regulator of the earth’s climate system. The oceans control the timing and magnitude of changes in the global climate system, primarily through the absorption of CO2 and heat. Other global climate impacts include arctic sea ice reduction, cyclonic storms, changes in ocean circulation, and changes in biodiversity and fisheries.

The symposium, “The Ocean in a High-CO2 World” was held October 2008 at Monaco under the auspices of the Scientific Committee on Oceanic Research and the Intergovernmental Oceanographic Commission of UNESCO. The meeting brought together 220 scientists from 32 countries to assess the impacts of ocean acidification on marine chemistry and ecosystems, including future scenarios of ocean acidification, effects of changes in seawater chemistry on nutrients, mechanisms of calcification and impacts on benthic and pelagic calcifiers, fisheries and food webs, and feedbacks to the climate system. The symposium also addressed acidification issues related to intentional sub-seabed storage of CO2, impacts on economics, and links with policy.

The ocean absorbs CO2 from the atmosphere at a rate of more than 20 million tons per day, removing one-fourth of the anthropogenic CO2 emitted to the atmosphere each year and reducing climate-change impacts of this “greenhouse gas”. When CO2 dissolves in seawater, it forms carbonic acid. As this ocean acidification continues, it decreases ocean pH and the concentration of carbonate ion, the basic building block of the shells and skeletons of many marine organisms. Within only a few decades, surface waters in the coldest parts of the ocean are projected to start becoming corrosive to the calcium carbonate shells of some marine organisms. Many things, including the potential for organisms to adapt and how effects move through ecosystems, need to be studied to understand ecological and economical impacts.

A European project on ocean acidification, or EPOCA, was launched in June 2008 to advance understanding of the biological, ecological, biogeochemical, and societal implications of ocean acidification, and documenting the changes in ocean chemistry and biogeography across space and time. It will determine the sensitivity of marine organisms, communities and ecosystems to ocean acidification, and integrate impacts of ocean acidification on marine ecosystems in biogeochemical, sediment, and coupled ocean-climate models. This will be done to understand and predict the responses to ocean acidification. Last, it will assess uncertainties, risks and thresholds or "tipping points" related to ocean acidification, at scales ranging from sub-cellular to ecosystemic, and from local to global.

At the same time that European research considers the impacts of ocean acidification, Europe is also considering initiatives to sequestering greenhouse gases under the seabed. This sequestration of CO2 could mitigate climate change and reduce ocean acidification. It could also increase the acidity of the oceans and regional seas if leakage of stored CO2 occurs. All these factors indicate the complexity of marine climate issues and adaptive and mitigative responses.

References

Case Study: Climate Change and European Coast and Beach Management, 2006, Completed by M.A.K.Muir for EU-funded Coastal Practise Network (CoPraNet)
The main author of this article is Magdalena Muir
Please note that others may also have edited the contents of this article.

The 2nd symposium, “The Ocean in a High-CO2 World” was held during 6-9 October 2008 at the Oceanography Museum of Monaco, sponsored by Scientific Committee on Oceanic Research (SCOR) and the Intergovernmental Oceanographic Commission of UNESCO (UNESCO-IOC) as well as the International Atomic Energy Agency’s Marine Environment Laboratories and the International Geosphere-Biosphere Programme. International Geosphere-Biosphere Programme hosts conference information at http://igbp-scor.pages.unibe.ch/news.html.

EU FP7 Integrated Project EPOCA (European Project on OCean Acidification) was launched in June 2008 for 4 years. The EPOCA consortium brings together more than 100 researchers from 27 institutes and 9 European countries (Belgium, France, Germany, Iceland, The Netherlands, Norway, Sweden, Switzerland, United Kingdom). Further information is available at http://www.epoca-project.eu