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Thursday, July 06, 2006

Rising Carbon Dioxide Levels Threaten Marine Organisms and Ecosystems

A new report warns that worldwide emissions of carbon dioxide from fossil fuel burning are dramatically altering ocean chemistry and threatening marine organisms, including corals, which secrete skeletal structures and support oceanic biodiversity.

The landmark report - Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers - released earlier this week summarizes the known effects of increased atmospheric carbon dioxide on these organisms, known as marine calcifiers, and recommends future research for determining the extent of the impacts.

"It is clear that seawater chemistry will change in coming decades and centuries in ways that will dramatically alter marine life," says Joan Kleypas, the report's lead author and a scientist at the National Center for Atmospheric Research (NCAR) in Boulder. "But we are only beginning to understand the complex interactions between large-scale chemistry changes and marine ecology. It is vital to develop research strategies to better understand the long-term vulnerabilities of sensitive marine organisms to these changes."

The report warns that oceans worldwide absorbed approximately 118 billion metric tons of carbon between 1800 and 1994. Oceans are naturally alkaline, and they are expected to remain so, but the interaction with carbon dioxide is making them less alkaline and more acidic. The increased acidity lowers the concentration of carbonate ion, a building block of the calcium carbonate that many marine organisms use to grow their skeletons and create coral reef structures.

"This is leading to the most dramatic changes in marine chemistry in at least the past 650,000 years," says Richard Feely, one of the authors and an oceanographer at NOAA's Pacific Marine Environmental Laboratory (PMEL) in Seattle.

The report follows a workshop funded by the National Science Foundation and the National Oceanic and Atmospheric Administration, and hosted by the U.S. Geological Survey Integrated Science Center in St. Petersburg, Florida.

Slowing skeletal growth

Experimental studies, such as those conducted by one of the report's authors, Chris Langdon at the University of Miami, show that coral calcification consistently decreases as the oceans become more acidic. This means that these organisms will grow more slowly, or their skeletons will become less dense, a process similar to osteoporosis in humans. As a result, reef structures are threatened because corals may be unable to build reefs as fast as erosion wears away the reefs.

"This threat is hitting coral reefs at the same time that they are being hit by warming-induced mass bleaching events," Langdon says. Mass bleaching occurs when unusually warm temperatures cause the coral to expel the colorful microscopic algae that provide the coral polyps with food.

Many calcifying organisms - including marine plankton such as pteropods, a planktonic marine snail [see image above] - are affected by the chemistry changes. Shelled pteropods are an important food source for salmon, mackerel, herring, and cod. If calcifying organisms such as pteropods are unable to sustain their populations, many other species may be affected.

"Decreased calcification in marine algae and animals is likely to impact marine food webs and has the potential to substantially alter the biodiversity and productivity of the ocean," says Victoria Fabry of California State University, San Marcos, who is another of the report's authors.

Threats to major ecosystems

Several other major ecosystems that are supported by marine calcifiers may be particularly threatened by ocean acidification. These include cold-water reefs, which are extensive structures that provide habitat for many important fish species, particularly in the coastal waters of Alaska.

The report outlines future research to understand this consequence of climate change. While scientists cannot yet fully predict how much marine calcification rates will change in the future, the report warns that the more critical question is: "What does this mean in terms of organism fitness and the future of marine ecosystems?"

Lisa Robbins of the U.S. Geological Service Center for Coastal and Watershed Studies and Chris Sabine of NOAA's Pacific Marine Environmental Laboratory also co-authored the report.

[Not good, not good...]


  • Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers

  • [A hat tip to Green Car Congress]


    Heiko said...

    After looking at the report I must say that I am no more worried about the issue than before, and that's not much.

    As far as I am concerned, all that matters is whether the ocean is productive and "pretty". Neither matter is seriously threatened. At best the evidence indicates that calcifying ecosystems may change substantially in some places.

    Also, ocean productivity isn't that big a deal, because in truth most of the ocean is about as productive as Antarctica or the Sahara. This is so, as micro-nutrients are missing in the open ocean. There's plenty of water and sunshine there, but with the nutrients sunk to the (more or less completely dark) ocean floor, hardly anything grows there.

    The oceans are only productive in a few places where nutrients upwell with cold water. Even though the oceans make up some 3/4 of the world's surface a fish take of 100 million tonnes per year is already straining fish populations, while we can produce 2 billion tonnes of grain on a tiny fraction (I think less than 5%) of the world's land.

    Jesse Jenkins said...

    I'm less worried about ocean productivity than I am about being responsible for the mass extinction of dozens of ocean species (and terrestrial species as well) due to anthropogenic climate change.

    Sure, we humans are wily creatures and will likely adapt with out too much trouble ... on a species level, of course; hundreds of millions will no doubt suffer, often in the most underdeveloped portions of the world where people are, of course, least responsible for the greenhouse gases causing their suffering. This is a clear case of gross environmental injustice, and we in the developed world have to own up to our responsibilities for this effect of climate change. That means attempting to mitigate climate change's most sever effects by both stabalizing and reducing greenhouse gas emissions and also working proactively as well as reactively to aid those suffering from climate change-induced droughts, famines, floods, sea level enchroachment, desertification, etc...

    And yes, the Earth will adapt, as it has in the past, and will go on living healthy - with or without us - ... eventually ... with new species filling the niches left open by the countless species whose extinction we will have caused. But unlike in the past, when volcanic eruptions or meteors or ice ages have caused similar mass extinctions, this time, it's on us. We're to blame for the massive loss of biodiversity that will take centuries or more to recover to the level it was at before we started tampering - and in my mind, that changes things considerably.

    So yes, we can quote the wise George Carlin and say, 'the Earth will be fine, we're the one's that need saving' ... but saying 'the Earth will be fine' ignores the countless inhabitants of this Earth, both human and otherwise, that will suffer and die in the meantime.

    Heiko said...

    Species extinction is a bit like the debate on abortion. If you think that embryos are nothing but a small bunch of cells, then your assessment of the rights and wrongs of abortion will differ than if your thinking is that's a human being that's being killed.

    Now I do take the moral view that species as such are not worthy of being saved. I do like dolphins, coral reefs, I want money spent on conservation, but if some deep sea worm or arctic moss or tropical dung beetle dies out I am not overly bothered.

    And I do think that it'll be primarily species that are small in every respect (from stature to their range) that will go extinct (and I am not sure what the numbers are even for those, is it 2% or 50% by 2100?). Dolphins or polar bears we'll feed directly if all else fails and create special sanctuaries for them.

    The "small" species I think have a pretty high turnover anyway (ie quick speciation and extinction).

    For major species, I don't think that species extinction today and over the 21st century will be comparable to those of past major extinctions. I think we'll make sure that nearly all major mammals and large birds will survive the 21st century.

    I do hugely care about developing countries, and think that expenditure on education and health care, and investment in infrastructure, is what they need above all, and that we'll help them much more efficiently that way than by incrementally doing more on climate change.

    I accept that most damage from climate change will likely be in tropical countries. That's what most economic and impact modelling says (ie countries like Canada or Russia ought to benefit, and if they don't, they'll suffer a lot less than Ecuador or Nigeria).