Sunday, August 1, 2010

Ocean Acidification: additional not-so-fun facts

A new term that more and more of the general public is hearing about is ocean acidification - the process whereby the pH level of the oceans is lowered, making it more acidic. This effect is a byproduct of global CO2 emissions and has been documented as having a negative effect on many forms of shellfish and other creatures that depend on the use of calcium carbonate in their development (calcium carbonate is broken down in the acidification process).

Much has been written about how ocean acidification will impact coral reefs, as calcium carbonate is a major component of the supporting skeleton of reef-building corals. But tropical waters are not the only locales affected. The Seattle Times recently reported on the effects of ocean acidification on Pacific oysters fields both in the wild and in commercial oyster farms.

The deep waters off the northwest shores of Oregon and Washington are much more highly acidic than the ongoing average (even with the "average" becoming more acidic, these waters
are still higher than shallower waters). For commercial oyster farms who pull in seawater to help raise oyster larvae, as long as the winds blow in the right direction, they appear to be relatively free from harm.

But winds can blow in ways that move surface water and draw in water from below - an upwelling as it is called. And this can spell trouble for the oysters, especially those living in the wild. The lowering of the pH (raising the acidic level) impacts the growth of new larvae, baby oysters, and even the reproductive cycles of adult oysters. Pacific oysters have not reproduced in the waters off Washington state's coast in six seasons.

"Nobody had thought about those upwelling events," said NOAA oceanographer Richard Feely. "They didn't predict any impacts along the coast until we observed them."

But oysters and other shell fish are not the only creatures potentially affected by corrosive, acidic waters. Changing the ocean's pH can have impacts on an animal's behavior and even the ocean's acoustical properties.

The Seattle Times listed these additional disturbing facts as a result of acidification:
  • The metabolism of squid can change, making them more lethargic - perhaps affecting their hunting ability and susceptibility to predation.
  • Acidic waters affect the way young fish larvae seek out prey and can actually be drawn to predators. An Australian researcher discovered that clownfish and some damselfish larvae get confused in corrosive water and seek out the smell of rock cod - one of their own predators.
  • Water with a lower pH has a different density, and so acidification changes the acoustical properties of seawater, essentially making it a noisier place. This could impact whales and dolphins that rely on their underwater sonar or echolocation for hunting.
But what concerns researchers the most in the Pacific Northwest is the fundamentals. "What I'm most worried about is the bottom of the food chain, things such as plankton and other small sea creatures," said John Guinotte, a marine biogeographer with the Marine Conservation Biology Institute in Bellevue, Washington. "We've got some of the lowest pH levels found anywhere, but we don't have any idea what the biological impacts are."

Through our actions, we are pushing the oceans into a brave new world, one in which it may adapt but not without serious consequences to a wide range of animal species, including mankind.

Read the Seattle Times article.

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