Feb 19, 2008
AAAS "seas" the future
Oceans were a big feature at the American Association for the Advancement of Science (AAAS) Annual Meeting in Boston - "America's science town" as AAAS president David Baltimore put it. But the news wasn't too positive.
Firstly, Ben Halpern of the University of California, Santa Barbara and colleagues announced their new map of the impact of human activities on the world's oceans. Only 4% showed relatively low effects – mainly around the poles – while more than 40% were heavily impacted.
"All types of human activity are affecting the oceans, not just climate change and fishing," said Halpern. "Our results show that when these and other individual impacts are summed up, the big picture looks much worse than I imagine most people expected. It was certainly a surprise to me."
But while Halpern's map showed that the polar oceans are so far relatively unscathed by man, Richard Aronson of Dauphin Island Sea Lab explained how warming waters may soon enable shell-crushing predators such as crabs and sharks to invade Antarctic ecosystems. Their presence could have a devastating effect on communities that have probably remained unchanged since they evolved in the absence of such predators around 40 million years ago. Alien species have also been entering Antarctic waters through the release of water used as ballast in research and tourist ships.
"Antarctica is the last stand for pristine marine communities," said Aronson. "This is an aesthetic and moral issue – it's about the way we want our planet to look for future generations."
As if oceans didn't have enough to contend with from rising temperatures, the increase in carbon dioxide in the atmosphere is leading to acidification of the seas as they absorb more of the gas. This acidification reduces the amount of carbonate available to organisms that need to build a calcium carbonate shell, such as corals, crabs, some plankton, scallops and sea urchins.
Gretchen Hofmann of the University of California, Santa Barbara called this simultaneous acidifying and warming a "double jeopardy". Corals, for example, are being in pulled in two directions – while rising temperatures force them to higher latitudes to avoid effects such as coral bleaching, ocean acidification pushes them back towards the equator as waters nearer the poles tend to contain even less carbonate.
Hofmann has been doing laboratory studies of the effect of changing atmospheric carbon dioxide concentrations on pterapod larvae. When adult, these lentil-sized ocean-dwelling snails are the "potato chips of the ocean" as they form a vital part of the food chain in both Antarctic and Arctic oceans. Hofmann has found that larvae grown under higher carbon dioxide conditions formed shorter and stumpier skeletons. Most worryingly, the organisms were much more sensitive to heat stress than larvae brought up under more normal atmospheres.
In a desperate attempt to find a positive note to end on, the last word from the AAAS meeting must go to Jack Barth of Oregon State University. Given one minute to sum up his views at the end of a symposium on the effects of climate change on the oceans, he said: "Every summer I have a conversation with my father in-law about climate change and we've made remarkable progress."
About the author
Liz Kalaugher is editor of environmentalresearchweb.