Acidic oceans, especially at poles – 10/01/2005

  • November 22, 2013 at 2:48 am #1043

    Acidic oceans threaten marine food chain

    Ian Sample, science correspondent
    Thursday September 29, 2005
    The Guardian

    Rising carbon dioxide in the atmosphere is threatening to make oceans
    too corrosive for marine organisms to grow protective shells,
    according to researchers.

    If emissions continue unabated, the entire Southern Ocean, which
    stretches north from the Antarctic coastline, and subarctic regions
    of the Pacific Ocean will soon become so acidic that the shells of
    marine creatures will soften and dissolve making them easy targets
    for predators. Others will not be able to grow sufficient shells to

    The loss of shelled creatures at the lower end of the food chain
    could have disastrous consequences for larger marine animals. North
    pacific salmon, mackerel, herring, cod and baleen whales all feed on
    pteropods or sea butterflies, one of the species under imminent

    “These are extremely important in the food chain and what happens if
    they start to disappear is a great unknown,” said Jim Orr, lead
    scientist on the study at the Laboratory for Science of the Climate
    and Environment in Gif-sur-Yvette, near Paris.

    Previous studies have suggested it would take centuries for emissions
    to acidify the oceans to such an extent, but the latest report,
    published today in the journal Nature, claims entire ecosystems will
    be threatened much sooner. “Within decades, there may be serious
    trouble brewing in these polar oceans,” said Dr Orr. “Unlike climate
    predictions, the uncertainties here are small.”

    Carbon dioxide is churned out by the burning of fossil fuels and
    other industrial processes. Each day, the average person burns enough
    fuel to emit 11kg (about 24lbs) of carbon dioxide, 4kg of which is
    absorbed by the oceans. When carbon dioxide is taken up by oceans, it
    strips out carbonate ions dissolved in surface waters, so there is
    less available for marine organisms to build calcium carbonate shells
    and exoskeletons from.

    Dr Orr and an international team from Britain, the US, Japan and
    Australia combined recent measurements from oceans with computer
    models to work out how CO2 levels are likely to change the acidity of
    oceans in coming decades if emissions continue as expected.

    They found that by 2100, the amount of carbonate available for marine
    organisms would drop by 60%. By 2050, there could be too little
    carbonate in surface waters for organisms to form shells.

    In a follow-up experiment, Victoria Fabry at California State
    University San Marcos investigated how marine organisms reacted to
    the predicted changes by immersing live pteropods in sea water as
    acidic as the models predicted for 2100. She found the shells began
    to dissolve rapidly, with pits forming on their surfaces and external
    layers peeling away.

    Life in the polar oceans will be first to feel the brunt of rising
    carbon dioxide levels. Atmospheric carbon dioxide has increased from
    pre-industrial levels of around 280 parts per million to 380ppm today.

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