Clams are delicious, nutritious and fun to find at the beach, but did you know that they can also be detectives?
These incredible bivalves can be used to help us find clues on how our environment becomes polluted, so that we can stop pollution where it starts, and protect our water sources!
How can an animal with no head, no arms and no legs tell us about the health of the ocean?
Clams may have no way to communicate with us, but they certainly can be used to help indicate the health of the waters they live in. Clams are bivalve mollusks, meaning they have two hard shells protecting them from predators, held together by a hinge joint, ligaments and adductor muscles (for a great lesson on clam dissection, click here!). They mostly feed on phytoplankton, which they filter out from the water around them.
Using their incurrent siphon, clams draw water into their protected shell palace. They then strain out organic particles from the incoming water using their gills, and sweep the food towards their mouth with the help of a layer of mucus. The water is then pushed out of clam's shell using the excurrent siphon. That's why you might see a clam squirt at you at the beach!
Clams are clever at filtering their food, but unfortunately they sometimes get more than what they bargained for. Along with their favorite phytoplankton, sometimes bivalves also pick up less desirable substances such as pesticides, lead, arsenic and PCB's (polychlorinated biphenyls). These pollutants accumulate in the delicate tissues of the clams, and are also traceable in their calcium carbonate shells. This process, known as bioaccumulation, is detrimental to the functioning of the clam, and also detrimental to the organisms that rely on clams for food- and that includes us.
Fortunately, scientists have found a way to use the cleaning power of clams to help indicate environmental pollution. Researchers are now placing clams in waterways and shorelines where pollution might be present. After several months of letting the animals grow and interact with the environment, scientists can retrieve the clams and conduct a chemical analysis on the clam's tissues. Using stable isotope techniques, the flesh of the clam can be analyzed to let the scientists know what kind of contaminants are present in that particular location.
Not only will this research help us understand where chemicals are present, it may also help us determine their origin. Clams placed near rivers and industrialized coastlines, are compared to clams in other locations to see which locations are the most polluted. For more information on this type of research, check out the work of Dr. Ruth H. Carmichael and her colleagues at the Dauphin Island Sea Lab!
It isn't just scientists that are using clams for detective work, students are also getting involved in the process! High school students in Washington are teaming up with Dr Harriette Phelps, Ph.D., a biologist at the University of the District of Columbia, to help understand how chemical contaminants are entering their local waters. Check out this great article from Science Today to learn about how they're doing it!
It's pretty amazing that we can use filter feeders to help understand and mediate environmental impacts!
For lesson plans on clams in the class room, check out:
Clam Vocabulary from the Down East Institute for Applied Marine Research and Education:
Some cool clam crafts from about.com:
A great comparative lesson for middle school students on clams and squid from Betterlesson.com:
American Geophysical Union. "Clam Cleanup-Biologists Clam up Waterways to Determine Sources of Pollution. Science Daily Journal Online Article. Published January 1, 2009. Retreived January 17, 2014.
Biology Junction "Clam Dissection." Web article.
Dauphin Island Sea Lab. "These Shells Don't Clam Up: Innovative Technique To Record Human Impact On Coastal Waters."ScienceDaily, 13 Dec. 2008. Web.
Klappenbach, L. "Bivalves." About.com article. 2014. http://animals.about.com/od/molluscs/p/bivalves.htm