Archive for May, 2009

Carbon fixation prediction during a bloom of Emiliania huxleyi is highly sensitive to the assumed regulation mechanism

Large scale precipitation of calcium carbonate in the oceans by coccolithophorids plays an important role in carbon sequestration. However, there is a controversy on the effect of an increase in atmospheric CO2 concentration on both calcification and photosynthesis of coccolithophorids. Indeed recent experiments, performed under nitrogen limitation, revealed that the associated fluxes may be slowed down, while other authors claim the reverse. We designed models to account for various scenarii of calcification and photosynthesis regulation in chemostat cultures of Emiliania huxleyi, based on different hypotheses on the regulation mechanism. These models consider that either carbon dioxide, bicarbonate, carbonate or calcite saturation state (Ω) is the regulating factor. All were calibrated to predict the same carbon fixation rate in nowadays pCO2, but they turn out to respond differently to an increase in CO2 concentration. Thus, using the four possible models, we simulated a large bloom of Emiliania huxleyi. It results that models assuming a regulation by CO32− or Ω predicted much higher carbon fluxes. The response when considering a doubled pCO2 was different and models controlled by CO2 or HCO3 − led to increased carbon fluxes. In addition, the variability between the various scenarii proved to be in the same order of magnitude than the response to pCO2 increase. These sharp discrepancies reveal the consequences of model assumptions on the simulation outcome.
Continue reading ‘Carbon fixation prediction during a bloom of Emiliania huxleyi is highly sensitive to the assumed regulation mechanism’

Sofja Kovalevskaja Award

Submit an application if you are a successful top-rank junior researcher from abroad, only completed your doctorate with distinction in the last six years, and have published work in prestigious international journals or publishing houses. The Sofja Kovalevskaja Award allows you to spend five years building up working groups and working on a high-profile, innovative research project of your own choice at a research institution of your own choice in Germany.

Scientists and scholars from all disciplines may apply directly to the Alexander von Humboldt Foundation. The Humboldt Foundation plans to grant up to eight Sofja Kovalevskaja Awards. The award is valued at 1.65 million EUR.

The Humboldt Foundation web site.

Shellfish face an uncertain future in high carbon dioxide world

Overfishing and disease have decimated shellfish populations in many of the world’s temperate estuarine and coastal ecosystems. Smithsonian scientists, led by Whitman Miller, ecologist at the Smithsonian Environmental Research Center in Edgewater, Md., have discovered another serious threat to these valuable filter feeders—rising levels of atmospheric carbon dioxide that contribute to the acidification of open ocean, coastal and estuarine waters.

Their findings are being published in PLoS One.

For shellfish and other organisms that have calcium carbonate shells and structures, the problem begins when atmospheric CO2 dissolves in seawater and creates carbonic acid that is then rapidly transformed into carbonate and bicarbonate ions in the water. Increased acidity tips the balance toward bicarbonate formation and away from carbonate. Less carbonate in the water means that shellfish have fewer building blocks to generate their shells. If the water is acidic enough, shells can even begin to dissolve.

“Estuarine and coastal ecosystems may be especially vulnerable to changes in water chemistry caused by elevated CO2 because their relative shallowness, reduced salinity and lower alkalinity makes them inherently less buffered to changes in pH than in the open ocean,” said Miller. For many calcifying organisms, CO2-induced acidification poses a serious challenge because these organisms may experience reduced rates of growth and calcification that “when combined with other environmental stresses, could spell disaster.”
Continue reading ‘Shellfish face an uncertain future in high carbon dioxide world’

Shellfish face an uncertain future in a high CO2 world

Overfishing and disease have decimated shellfish populations in many of the world’s temperate estuarine and coastal ecosystems. Smithsonian scientists, led by Whitman Miller, ecologist at the Smithsonian Environmental Research Center in Edgewater, Md., have discovered another serious threat to these valuable filter feeders—rising levels of atmospheric carbon dioxide that contribute to the acidification of open ocean, coastal and estuarine waters. Their findings are being published in the open-access, peer-reviewed journal PLoS ONE, May 27.

For shellfish and other organisms that have calcium carbonate shells and structures, the problem begins when atmospheric CO2 dissolves in seawater and creates carbonic acid that is then rapidly transformed into carbonate and bicarbonate ions in the water. Increased acidity tips the balance toward bicarbonate formation and away from carbonate. Less carbonate in the water means that shellfish have fewer building blocks to generate their shells. If the water is acidic enough, shells can even begin to dissolve.

“Estuarine and coastal ecosystems may be especially vulnerable to changes in water chemistry caused by elevated CO2 because their relative shallowness, reduced salinity and lower alkalinity makes them inherently less buffered to changes in pH than in the open ocean,” said Miller. For many calcifying organisms, CO2-induced acidification poses a serious challenge because these organisms may experience reduced rates of growth and calcification that “when combined with other environmental stresses, could spell disaster.”
Continue reading ‘Shellfish face an uncertain future in a high CO2 world’

Shellfish face uncertain future in high CO2 world: influence of acidification on oyster larvae calcification and growth in estuaries

Human activities have increased atmospheric concentrations of carbon dioxide by 36% during the past 200 years. One third of all anthropogenic CO2 has been absorbed by the oceans, reducing pH by about 0.1 of a unit and significantly altering their carbonate chemistry. There is widespread concern that these changes are altering marine habitats severely, but little or no attention has been given to the biota of estuarine and coastal settings, ecosystems that are less pH buffered because of naturally reduced alkalinity.
Continue reading ‘Shellfish face uncertain future in high CO2 world: influence of acidification on oyster larvae calcification and growth in estuaries’

Feds open comment on Arctic fisheries proposal

A federal agency says it will open a public comment period on a proposal to prohibit commercial fishing in Arctic waters in the Beaufort and Chukchi seas.

The North Pacific Fishery Management Council adopted the plan in February. That plan is now open for public review. It still needs the final approval of the Secretary of Commerce.

The plan has been hailed by environmentalists and industry representatives alike, who say summertime melting of sea ice has increased interest in commercial fishing in the Arctic.
Continue reading ‘Feds open comment on Arctic fisheries proposal’

Elevated water temperature and carbon dioxide concentration increase the growth of a keystone echinoderm

Anthropogenic climate change poses a serious threat to biodiversity. In marine environments, multiple climate variables, including temperature and CO2 concentration ([CO2]), are changing simultaneously. Although temperature has well-documented ecological effects, and many heavily calcified marine organisms experience reduced growth with increased [CO2], little is known about the combined effects of temperature and [CO2], particularly on species that are less dependent on calcified shells or skeletons. We manipulated water temperature and [CO2] to determine the effects on the sea star Pisaster ochraceus, a keystone predator. We found that sea star growth and feeding rates increased with water temperature from 5 °C to 21 °C. A doubling of current [CO2] also increased growth rates both with and without a concurrent temperature increase from 12 °C to 15 °C. Increased [CO2] also had a positive but nonsignificant effect on sea star feeding rates, suggesting [CO2] may be acting directly at the physiological level to increase growth rates. As in past studies of other marine invertebrates, increased [CO2] reduced the relative calcified mass in sea stars, although this effect was observed only at the lower experimental temperature. The positive relationship between growth and [CO2] found here contrasts with previous studies, most of which have shown negative effects of [CO2] on marine species, particularly those that are more heavily calcified than P. ochraceus. Our findings demonstrate that increased [CO2] will not have direct negative effects on all marine invertebrates, suggesting that predictions of biotic responses to climate change should consider how different types of organisms will respond to changing climatic variables.
Continue reading ‘Elevated water temperature and carbon dioxide concentration increase the growth of a keystone echinoderm’

Rate of Iceland Sea acidification from time series measurements

The Iceland Sea is one part of the Nordic Seas. Cold Arctic Water prevails there and the deep water is an important source of North Atlantic Deep Water. We have evaluated time series observations of measured pCO2 and total CO2 concentration from discrete seawater samples during 1985–2008 for changes in response to increasing atmospheric carbon dioxide. The surface pH in winter decreases 0.0024 yr−1, which is 50% faster than those at two subtropical time series stations, BATS and ESTOC. In the deep water regime (>1500 m), the rate of pH decline is ¼ of that observed in surface waters. The surface calcium carbonate saturation states (Ω) are about 1.5 for aragonite and 2.5 for calcite, and are about ½ those for subtropical waters. During the period 1985–2008, the degree of saturation (Ω) decreased at a rate of 0.0072 yr−1 for aragonite and 0.012 yr−1 for calcite. The aragonite saturation horizon is currently at 1750 m and rising at 4 m yr−1. Based on local hypsography, each year causes 800 km2 of sea floor, previously bathed in saturated waters, to be exposed to undersaturation conditions.
Continue reading ‘Rate of Iceland Sea acidification from time series measurements’

IAEA marine scientists warn of dangers of ocean acidification

Scientists at the International Atomic Energy Agency, the IAEA, have joined forces with experts around the world to call for urgent action to control what they refer to as the “other C02 problem”.—ocean acidification

As carbon dioxide emissions into the atmosphere increase, acidity levels in the oceans are also increasing.

The oceans, which absorb large amounts of this greenhouse gas, are also increasing. Scientist James Orr says studies show that at the level of CO2 by the end of the century, mussels and oysters wont be able to build their shells properly:

“It’s estimated that in some waters, the ocean acidity level will get to the point where the shells will actually start dissolving. Not only will they not be able to form as well as in the past with higher acidity levels, but the chemical conditions of the water actually become corrosive to the shell itself so they could actually dissolve.”
Continue reading ‘IAEA marine scientists warn of dangers of ocean acidification’

The Gordon Research Conference in Chemical Oceanography

Process, Dynamics, And Change In The Anthropocene Ocean

2-7 August 2009, Tilton School, Tilton, New Hampshire, USA.

The Gordon Research Conference in Chemical Oceanography is a major forum for the discussion and exchange of ideas at the frontiers of a field that encompasses the chemical components, reaction mechanisms, and biogeochemical processes within the ocean, present and past, and at its interfaces with the atmosphere and solid earth. The main purpose of the conference is to bring together many of the leading contributors in the chemical oceanography research community (from academic, industry and government laboratories) with a healthy mix of young scientists (junior faculty, postdocs, graduate students) to discuss and disseminate the significant new advances shaping this highly interdisciplinary field. Productive cross-fertilization of ideas and the establishment of scientific connections for future research are also conference goals.

2 sessions related to ocean acidification on Monday 3 August 2009:

  • Ocean Acidification, Carbonates, and Biogeochemical Responses
  • Biomineralization and Ocean Process / State Proxies

Continue reading ‘The Gordon Research Conference in Chemical Oceanography’


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Ocean acidification in the IPCC AR5 WG II

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