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 phytoplankton
Flora of freely floating, often minute organisms that drift with water currents. Like land vegetation, phytoplankton uses carbon dioxide, releases oxygen, and converts minerals to a form animals can use. . 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 (body) State University of New York - (SUNY) The public university system of New York State, USA, with campuses throughout the state. (SUNY SUNY - State University of New York ) 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 seawater
Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. .
The selenium selenium (səlē`nēəm), nonmetallic chemical element; symbol Se; at. no. 34; at. wt. 78.96; m.p. 217°C;; b.p. about 685°C;; sp. gr. 4.81 at 20°C;; valence −2, +4, or +6. , lead, cobalt, and americium americium (ămərĭ`shēəm), artificially produced radioactive chemical element; symbol Am; at. no. 95; mass no. of most stable isotope 243; m.p. about 1,175°C;; b.p. about 2,600°C;; sp. gr. 13. 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 contaminant /con·tam·i·nant/ (kon-tam´in-int) something that causes contamination.
something that causes contamination. 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 mussel, edible freshwater or marine bivalve mollusk. Mussels are able to move slowly by means of the muscular foot. They feed and breathe by filtering water through extensible tubes called siphons; a large mussel filters 10 gal (38 liters) of water per day. , 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.