Archive for September, 2006

pH variability and CO2 induced acidification in the North Sea

A coupled carbonate system–marine ecosystem–hydrodynamic model is used to simulate the temporal and spatial variability in pH across the southern North Sea as it relates to the environmental and biological processes affecting CO2, namely, photosynthesis and respiration, riverine boundary conditions and atmospheric CO2 concentrations. Annual pH ranges are found to vary from 1.0 in areas influenced by riverine signals, consistent with observations and previous studies. It is shown that benthic, as well as pelagic, activity is an important factor in this variability. The acidification of the region due to increased fluxes of atmospheric CO2 into the marine system is calculated and shown to exceed, on average, 0.1 pH units over the next 50 years and result in a total acidification of 0.5 pH units below pre-industrial levels at atmospheric CO2 concentrations of 1000 ppm. The potential for measurable changes in biogeochemistry are demonstrated by simulating the observed inhibition of pelagic nitrification with decreasing pH. However, we conclude that there is a lack of knowledge of how acidification might affect the complex interaction of processes that govern marine biogeochemical cycles and a consequent need for further research and observations.

Blackford J. C. & Gilbert F. J., 2007. pH variability and CO2 induced acidification in the North Sea. Journal of Marine Systems 64(1-4): 229-241. Article.

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Microbial community in a sediment-hosted CO2 lake of the southern Okinawa Trough hydrothermal system

Increasing levels of CO2 in the atmosphere are expected to cause climatic change with negative effects on the earth’s ecosystems and human society. Consequently, a variety of CO2 disposal options are discussed, including injection into the deep ocean. Because the dissolution of CO2 in seawater will decrease ambient pH considerably, negative consequences for deep-water ecosystems have been predicted. Hence, ecosystems associated with natural CO2 reservoirs in the deep sea, and the dynamics of gaseous, liquid, and solid CO2 in such environments, are of great interest to science and society. We report here a biogeochemical and microbiological characterization of a microbial community inhabiting deep-sea sediments overlying a natural CO2 lake at the Yonaguni Knoll IV hydrothermal field, southern Okinawa Trough. We found high abundances (>109 cm–3) of microbial cells in sediment pavements above the CO2 lake, decreasing to strikingly low cell numbers (107 cm–3) at the liquid CO2/CO2-hydrate interface. The key groups in these sediments were as follows: (i) the anaerobic methanotrophic archaea ANME-2c and the Eel-2 group of Deltaproteobacteria and (ii) sulfur-metabolizing chemolithotrophs within the Gamma- and Epsilonproteobacteria. The detection of functional genes related to one-carbon assimilation and the presence of highly 13C-depleted archaeal and bacterial lipid biomarkers suggest that microorganisms assimilating CO2 and/or CH4 dominate the liquid CO2 and CO2-hydrate-bearing sediments. Clearly, the Yonaguni Knoll is an exceptional natural laboratory for the study of consequences of CO2 disposal as well as of natural CO2 reservoirs as potential microbial habitats on early Earth and other celestial bodies.

Inagaki F., Kuypers M. M. M., Tsunogai U., Ishibashi J.-i., Nakamura K.-i., Treude T., Ohkubo S., Nakaseama M., Gena K., Chiba H., Hirayama H., Nunoura T., Takai K., Jorgensen B. B., Horikoshi K. & Boetius A., 2006. Microbial community in a sediment-hosted CO2 lake of the southern Okinawa Trough hydrothermal system. Proceedings of the National Academy of Science U.S.A. 103:14164-14169. Article

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Lakes of liquid CO2 in the deep sea

The thought of liquid CO2 conjures up different things to different folks: perhaps the decaffeination of coffee beans, perhaps the recently popularized “green” method for dry cleaning, or even phase diagrams that occupied a part of one’s life in past chemistry classes. What it does not conjure up is a subsurface lake at the bottom of the ocean, a lake with abundant living microbes, as reported in this issue of PNAS by Inagaki et al. (1). These authors discovered such a place near the Yonaguni Knoll in the Okinawa Trough at a depth of {approx}1,400 m. The description in both words and video (see supporting movie 1 in ref. 1) is quite striking. First, because liquid CO2 at this depth is less dense than water (2, 3), so that such a lake should not be present. Second, because this is a phenomenon that few of us have ever seen, movie 1 in ref. 1 reveals a flowing stream of liquid CO2 that seems almost surreal.

Kenneth N., 2006. Lakes of liquid CO2 in the deep sea. Proceedings of the National Academy of Science U.S.A. 103:13903-13904. Article

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Scientists fear that carbon dioxide is altering ocean chemistry

Fifty-five million years ago, Earth endured a period of rapid global warming, a shift so dramatic it altered ocean and atmospheric circulation, driving plankton in the seas and mammals on land to extinction.

The event, called the Paleocene-Eocene Thermal Maximum, may have been caused by volcanic eruptions that flooded the atmosphere with billions of tons of carbon dioxide. Or, methane gas frozen beneath the sea on continental shelves could have destabilized, diffusing into the atmosphere where it was oxidized into carbon dioxide.

As the oceans absorbed much of the carbon dioxide, their pH fell and they grew increasingly acidified.

Thirty percent to 40 percent of a major class of plankton, called foraminifera, went extinct.

Today, scientists look at that turn in Earth’s history with worry. Rising carbon dioxide emitted by the burning of gas, oil and other fossil fuels is being absorbed by the oceans – making them increasingly acidified once again.

Every day, about 22 million tons of carbon dioxide generated from human activities – primarily from the burning of fossil fuels – are entering the world’s oceans. That’s 10 times the rate at which carbon dioxide would be absorbed by the oceans if humans did not burn fossil fuels.

The Paramus Post, 24 September 2006- Article

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Acidités océaniques

C’est Cousteau qui mange son bonnet : à force d’absorber du CO2, son bel océan tourne au vinaigre. Coraux, plancton et même poissons sont menacés.

Le Point, 21 Septembre 2006- Article

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Race against extinction

Are marine organisms able to adapt to ocean acidification?
An international group of researchers under leadership of the Alfred Wegener Institute for Polar and Marine Research demands a stronger consideration of evolutionary adaptations in predictive models. For shell-forming marine algae the scientists compared laboratory experiments with fossil collections. Coccolithophorids – unicellular planktonic algae of only a few thousandths of millimetres – developed malformations of their calcium carbonate skeleton when grown experimentally in seawater of varying acidity. In contrast, fossils of the same species dating back to periods of various carbon dioxide concentrations had intact skeletons. The researchers conclude that the organisms’ ability to adapt to changing environmental conditions is greater than previously acknowledged in prediction models.

Alfred-Wegener-Institut für Polar- und Meeresforschung, 19 September 2006 – Press release

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Acid test

Changing ocean chemistry threatens to harm marine life

Fifty-five million years ago, Earth endured a period of rapid global
warming, a shift so dramatic it altered ocean and atmospheric
circulation, driving plankton in the seas and mammals on land to
extinction…

Bruce Lieberman, San Diego Union Tribune 14 September 2006 – Article

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Al Gore Interview: An Inconvenient Truth

Since losing the 2000 US election to George W. Bush, former Vice President Al Gore has focused his efforts on saving the planet from the devastating effects of global warming. The acclaimed new documentary “An Inconvenient Truth” follows Gore as he travels from city to city, inspiring people to make a difference and protect their futures.At a press conference in Sydney this week, Gore spoke candidly about the state of the environment, his dreams for a better world and the impact of global warming on Australia.

yourMovies.com.au

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We’re Killing Our Oceans

Labor Day is gone. The Shore is quiet now. Most beachgoers have
packed away chairs and umbrellas and turned their thoughts to school
and football.

But come Memorial Day, they’ll be back, expecting the solace,
nourishment or income they’ve always derived from the ocean. The
question is: What will they find?

The Philadelphia Enquirer, 12 September 2006 – Article

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Visitors signal a sea change

Fin whales delighted onlookers when they turned up for the first
time in Welsh climate-changed waters. But Sally Williams discovers that
their displacement could mean they are ‘not waving but drowning’

icWales 8 Sep. 2006 – Article

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