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Measuring the metal of mussels.

Scientists appreciate mussels not just for their taste but also for their value as indicators of water quality. The animals retain pollutants found in their aquatic habitat, withstand dirty environments, and remain in the same spot for all of their adult lives.

Now, new research is distinguishing which contaminants the mussels take in from the surrounding water and which they pick up from their food, phytoplankton. Although regulators usually measure dissolved pollutants to set water quality standards, contaminants in plants and sediment may sometimes prove more important, says Nicholas S. Fisher of the State University of New York (SUNY) at Stony Brook.

In two studies, Fisher and his colleagues examined the concentrations of seven coastal pollutants in two common, closely related mussels, Mytilus galloprovincialis and M. edulis.

They exposed the animals to water or phytoplankton laced with radioactive isotopes of these metals. After measuring the concentrations and locations of the isotopes in the mussels, the researchers put some of the animals in mesh cages off the Mediterranean coast for up to 4 months and left others in aquariums containing Mediterranean seawater.

The selenium, lead, cobalt, and americium stored in the mussels came mainly from phytoplankton, Fisher, Wen-Xiong Wang of SUNY at Stony Brook, and Samuel N. Luoma of the U.S. Geological Survey in Menlo Park, Calif., report in the Sept. 12 Marine Ecology Progress Series. The animals absorbed most of their cadmium from the water. Whether zinc and silver were absorbed primarily from water or food depended on the water conditions.

How much of each contaminant the mussels took in varied considerably. For instance, the animals absorbed 4 percent of the americium present in the food or water they consumed and about 60 percent of the silver, Fisher and his colleagues note in the November Environmental Science & Technology.

Once inside a mussel, the pollutants met with different fates. The animals took from 10 to 60 days, depending on the metal, to expel half of the original amount absorbed.

The authors developed a mathematical model for determining the relative importance of food and water as sources of pollutants in mussels. The model also predicts the amounts of the various metals that the animals will accumulate under varying water conditions.

The metals remain in the mussels' feces for different lengths of time, the team reports. Whereas half of the silver leached out in 18 days, it took 107 days for half of the americium to disperse. Studying mussel feces "sounds awfully obscure, I realize," says Fisher, but contaminants pass from fecal matter into the sediment, where worms and other fish foods dwell.
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Title Annotation:research on using mussels to measure water contamination
Author:Adler, Tina
Publication:Science News
Article Type:Brief Article
Date:Jan 11, 1997
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