January 1, 2009 Biologists are able to determine the sources of toxins in water by using clams as pollutant traps. Clams naturally clean water by feeding absorbing toxins in their tissues as they draw in water. By placing the clams downstream of industrial parks and highways, they can be analyzed for pollutants. Biologists open the clams after exposure to these waters and detach them from their shells-- various lab tests reveal contaminants in the waterway.
Many of our streams and rivers are contaminated with pollutants like pesticides, lead, arsenic and PCBs. It's a problem that's costly to clean up. Scientists are using a new, inexpensive way to fix the problem.
Lurking in many rivers and streams are contaminants. Some you can see, and some you can't. Hidden chemicals ruin waterways and everything in it. To clean things up, biologists are teaming up with local high school students to dredge up clams to use as tiny detectives. They help by finding the source of toxic leaks.
"We're using them as pollutant traps," said Harriette Phelps, Ph.D., a biologist at the University of the District of Columbia in Washington, D.C.
Students put the clams in streams that lead to rivers. Clams then suck in water swept down from industrial parks and highways.
"It's been a great experience to actually come and see them and be the ones to pick them up out of the water," student Caitlin Virta said.
Clams clean the water as they feed, absorbing toxins in their tissues. The clams are collected back from streams. Then, scientists pry open the clams and detach them from their shell. Later, lab tests reveals the clam's secret -- the kinds and quantities of pollutants in the water.
"We can trace them back to sources, and then hopefully we can go from there and get rid of the sources," Dr. Phelps said.
The clams detected a banned pesticide in Maryland, believed buried years ago and now slowly leaking. "I thought it was really cool how you could tell the health of a stream from analyzing clam leftovers," Virta said.
It's a cool way to clean up the environment.
BIOACCUMULATION AND CLAMS: Clams are filter-feeders, meaning they draw water into their shells, remove the food they find, and then draw in more food-rich water to continue feeding. This means that lots of water works its way through their shells. The muscle of the clam gathers not only food, but other material suspended in water during this process, which can lead to the accumulation of toxins and pollutants. Bioaccumulation is the term for toxins and pollutants that collect in the tissue of an organism. Biomagnification is a related term, referring to the transfer of such substances from prey to predator. If a prey animal bioaccumulates toxins in its body, then its predator, after consuming many of the smaller animals will accumulate many, many times the amount of the toxin in any one of their prey.
SECONDARY STANDARDS: Even if your tap water meets the EPA's basic requirement for safe drinking water, some people still object to the taste, smell or appearance of their water. These are aesthetic concerns, however, and therefore fall under the EPA's voluntary secondary standards. Some tap water is drinkable, but may be temporarily clouded because of air bubbles, or have a chlorine taste. A bleach-like taste can be improved by letting the water stand exposed to the air for a while.
The American Geophysical Union contributed to the information contained in the TV portion of this report.