Archive for January, 2007

Impact of CO2 Changes on Biogeochemical Processes and Ecosystem Functioning

PS009:  Impact of CO2 Changes on Biogeochemical Processes and Ecosystem Functioning

This symposium will bring together a multidisciplinary approach to consider the impact of a high CO2 world on the biological and biochemical processes within the ocean. There is now clear scientific consensus that the increasing atmospheric levels of CO2, resulting mainly from human activities, are causing environmental change. While we understand the chemical processes involved when CO2 from the atmosphere dissolves in seawater, we know little about the impact.

A range of coupled climate models has been developed to investigate the response of the physical ocean-atmosphere system to increased greenhouse gases and aerosols. These simulations predict increases in ocean temperatures, more salty water in the subtropics and fresher water at high latitudes, increased oceanic stratification and a reduction in the mixed layer depth, and changes in cloud cover and sea ice. In turn, these changes are highly likely to cause significant alteration in nutrient and light availability and the length of the growing season and, taken together, will severely alter biological community structure. For example, warmer more oligotrophic conditions could result in increases in cynobacteria, while increases in dust will induce more nitrogen-fixers.

In addition, there is now increasing concern about ocean acidity. The surface ocean pH is already 0.1 unit lower than pre-industrial levels and, by the end of the century, it will become another 0.3 – 0.4 units lower under the IS92a “business as usual” scenario. Experimental evidence suggests that if trends in ocean acidity continue, key marine organisms such as corals and coccolithophores will have difficulty in maintaining their calcium carbonate skeletons.
Contributions that address all the above issues are welcomed.

Conveners

Denise Smythe-Wright, National Oceanography Centre, Southampton, UK, dsw@noc.soton.ac.uk
James Orr, Laboratoire des Sciences du Climat et de l’Environment, CEA-CNRS, FRANCE, James.Orr@cea.fr
Jorge L. Sarmiento, AOS Program, Princeton University, USA, jls@Princeton.EDU

More information: IUGG 2007 Perugia

Effects of anthropogenic seawater acidification on acid–base balance in the sea urchin Psammechinus miliaris

The purple-tipped sea urchin, Psammechinus miliaris, was exposed to artificially acidified seawater treatments (pHw 6.16, 6.63 or 7.44) over a period of 8 days. Urchin mortality of 100% was observed at pHw 6.16 after 7 days and coincided with a pronounced hypercapnia in the coelomic fluid producing an irrecoverable acidosis. Coelomic fluid acid–base measures showed that an accumulation of CO2 and a significant reduction in pH occurred in all treatments compared with controls. Bicarbonate buffering was employed in each case, reducing the resultant acidosis, but compensation was incomplete even under moderate environmental hypercapnia. Significant test dissolution was inferred from observable increases in the Mg2+ concentration of the coelomic fluid under all pH treatments. We show that a chronic reduction of surface water pH to below 7.5 would be severely detrimental to the acid–base balance of this predominantly intertidal species; despite its ability to tolerate fluctuations in pCO2 and pH in the rock pool environment. The absence of respiratory pigment (or any substantial protein in the coelomic fluid), a poor capacity for ionic regulation and dependency on a magnesium calcite test, make echinoids particularly vulnerable to anthropogenic acidification. Geological sequestration leaks may result in dramatic localised pH reductions, e.g. pH 5.8. P. miliaris is intolerant of pH 6.16 seawater and significant mortality is seen at pH 6.63.

Miles H., Widdicombe S., Spicer J. I. & Hall-Spencer J., 2007. Effects of anthropogenic seawater acidification on acid-base balance in the sea urchin Psammechinus miliaris. Marine Pollution Bulletin 54(1): 89-96. Article.

Last warning: 10 years to save world

THE world has just 10 years to reverse surging greenhouse gas emissions or risk runaway climate change that could make many parts of the planet uninhabitable.

The Australian, 28 January 2007. Article.

Ocean Surface CO2 Variability and Vulnerabilities Workshop

IOC/UNESCO, Paris, France, April 11-14 (Wednesday-Saturday), 2007

The purpose of this workshop is to review the current knowledge base and enhance international cooperation to resolve the magnitude, variability and processes governing ocean sources and sinks of carbon: from observations, process-based models and atmospheric and oceanic inversions. Some of the key questions to be addressed through plenary talks, poster session, and working groups include:

  • What are the decadal changes in the air-sea CO2 flux in the oceans today and how well can we predict their changes in the future?
  • Are present oceanic and atmospheric models simulating the observed changes?
  • How do changes in ocean physics (temperature, salinity, and circulation) and atmospheric dynamics impact air-sea CO2 fluxes today, in the future, and in the far future?
  • What is the possible contribution of changes in marine ecosystems on air-sea CO2 fluxes?
  • How can we use evidence from the present and the past to set bounds on the possible response of the carbon cycle to physical and biological changes in the future?
  • Are there instabilities and thresholds in the marine carbon cycle?
  • What is the current knowledge of regional and temporal variability in mixed-layer CO2 and air-sea CO2 fluxes?
  • Can we estimate how CO2 fluxes have changed in the coastal ocean?
  • What is the current knowledge and what are the future approaches to quantify gas transfer rates?
  • What processes have controlled the observed CO2 flux variability?
  • What observational strategies, instrumentation and model developments are required to deliver better air-sea CO2 flux estimates into the future

Web site

Cruising the sub-antarctic for clues to ocean acidification

The Minister for the Environment and Heritage, Senator Ian Campbell, said the Sub-Antarctic Zone Sensitivity to Environmental Change voyage will study the effects of increasing carbon dioxide on planktonic organisms – the microscopic plants and animals in the ocean – and the ability of the ocean to continue to process carbon.

“When carbon dioxide dissolves in the ocean it triggers chemical reactions that make the ocean more acidic,” Senator Campbell said. “This affects the ability of some planktonic organisms, including certain algae and snail-like pteropods, to form shells. It can also change the chemistry of dissolved nutrients, potentially causing large-scale changes in the structure of marine ecosystems.

Media Newswire, 18 January 2007. Press release.

Algal constraints on the Cenozoic history of atmospheric CO2?

An urgent question for future climate, in light of increased burning of fossil fuels, is the temperature sensitivity of the climate system to atmospheric carbon dioxide (pCO2). To date, no direct proxy for past levels of pCO2 exists beyond the reach of the polar ice core records. We propose a new methodology for placing an upper constraint on pCO2 over the Cenozoic based on the living geological record. Specifically, our premise is that the contrasting calcification tolerance of various extant species of coccolithophore to raised pCO2 reflects an “evolutionary memory” of past atmospheric composition. The different times of first emergence of each morphospecies allows an upper constraint of past pCO2 to be placed on Cenozoic timeslices. Further, our hypothesis has implications for the response of marine calcifiers to ocean acidification. Geologically “ancient” species, which have survived large changes in ocean chemistry, are likely more resilient to predicted acidification.

Henderiks J. & Rickaby R. E. M., 2007. Algal constraints on the Cenozoic history of atmospheric CO2? Biogeosciences Discussions 4: 1-11. Article.

Environmental problems indicate strained relationship with natural world

… The Great Lakes are small potatoes compared to the ocean, however, and the ocean is in a more perilous state now than we ever thought. It’s bad enough that the concentration of carbon dioxide in the air today is higher than it has been at any point in the past 650,000 years, but the effects of this one fact are enormous.

When carbon dioxide dissolves, it produces carbonic acid, which in turn has altered the ocean’s pH levels enough to have increased the ocean’s “acidification” by 30 percent. Because it takes the ocean so long to “turn over,” and because carbon dioxide also has “long life” in the atmosphere, it is impossible to reverse the acidification that has already taken place in the ocean.

Nevada Appeal, 17 January 2007. Article.

Climate-related increases in jellyfish frequency suggest a more gelatinous future for the North Sea

Data obtained since 1958 from the continuous plankton recorder show an increasing occurrence of jellyfish in the central North Sea that is positively related to the North Atlantic Oscillation (NAO) and Atlantic inflow to the northern North Sea. Since 1970, jellyfish frequency has been also significantly negatively correlated with mean annual pH, independent of NAO trends. Jellyfish frequency increased in the mid-1980s, coincident with the reported regime shift in the North Sea and tracking trends in phytoplankton color. As models produced under all climate-change scenarios indicate a move toward a positive NAO, and pH of the oceans is predicted to decrease with rising CO2, we suggest that jellyfish frequency will increase over the next 100 yr.
Attrill et al. (2007). Climate-related increases in jellyfish frequency suggest a more gelatinous future for the North Sea. Limnology and Oceanography 52(1): 480–48. Article.

Barbara Boxer’s global hot seat

This year is likely to be the hottest in history, according to Britain’s Met Office, thanks to a combination of El Nino and global warming.

While yet more climatological red flags will likely be raised throughout 2007, we’ll probably hear less from the world’s biggest oil company and an outgoing Republican senator that the latter is an illusion, or at least exaggerated.

Sen. Barbara Boxer, who takes over as chair of the Senate Environment and Public Works Committee, has promised that combatting climate change will be her top priority. While Congress will likely move “incrementally,” she vows that there will be a “sea change” in how the committee addresses environmental issues.

San Francisco Chronicle, 4 January 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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