Heavy Metals, Rising Temperatures A One-Two Punch To Oysters

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Newswise — Oysters exposed to high water temperatures and a common heavy metal are unable to obtain sufficient oxygen and convert it to cellular energy, according to a new study presented at The American Physiological Society conference, Comparative Physiology 2006.

The study showed how cadmium, a heavy metal, reduces the oyster’s tolerance of warmer water temperatures and makes it more vulnerable during the summer when water temperatures rise. Half of the oysters exposed to the pollutant in 28° C (82° F) water died within 20 days, said lead researcher Gisela Lannig. Oysters exposed to cadmium at lower temperatures showed much lower mortality rate, suggesting that the combination of high temperature and cadmium is more stressful than each of these conditions alone, she said.

The study “Temperature tolerance in the oyster, Crassostrea virginica, is affected by cadmium,” was carried out by Lannig, of the Alfred Wegener Institute for Polar & Marine Research, Bremerhaven, Germany, and Jason Flores and Inna Sokolova, of the University of North Carolina at Charlotte. The work was done in North Carolina. The researchers presented the study October 10 during a poster session at Comparative Biology 2006: Integrating Diversity in Virginia Beach.

Oysters once thrived in the coastal regions of much of the eastern United States, but over-fishing, global warming, rising ocean water temperatures and increased pollution have combined to reduce the oyster population to 5% of what it was 200 years ago, Sokolova said. The loss of oysters has far-reaching environmental implications. “We can’t even imagine the expanse of oyster reefs 100-200 years ago and their impact on the ecosystem,” Sokolova said. For example, a century ago, the oyster population could completely filter the water in the Chesapeake Bay in three days. Today, with the oyster population continuing to decline from poor water quality and disease, it would take a year to filter the same amount of water, she said. In addition to filtering water, oysters create a kind of reef that other marine life depends upon.

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