Reprinted from the Putnam Highlands Audubon Society Chapter Newsletter, Fall 2004, page 1.

The Worms of Foundry Cove: How They Contaminated the Food Chain and Later Showed a Successful Cleanup
Nancy P. Durr
	http://www.fcps.k12.va.us/StratfordLandingES/Ecology/mpages/aquatic_worm.htm

Once again Foundry Cove has made cadmium-based headlines, this time with the publication of a study entitled “Rapid loss of genetically based resistance to metals after the cleanup of a Superfund site.” On first reading of the title, one might think the loss of resistance was a bad thing, but not so; the loss of resistance actually reflects the recovery of the natural pre-pollution state of Foundry Cove. (Proceed-ings of the National Academy of Sciences (PNAS): 100(17):9889-9891, 8/1903)

How and Why Foundry Cove Became a Superfund Cleanup Site
Between 1953 and 1979 the Marathon Battery factory released some 53 tons of cadmium and nickel hydride wastes into Foundry Cove. The food chain became contaminated with cadmium (Cd). The Cd settled into the silt. Limnodrilus hoffmeisteri, a common and abundant deposit-feeding worm very important in turnover of the sediment where toxic metals accumulate, inadvertantly ingested the Cd along with its prey/food. The worms were, in turn, ingested by their predators. And so on, fully up the food chain, until fish-eating people were ingesting Cd.

The Worms Survive This Nasty Cadmium by Binding It
They made a protein that binds to Cd, making the Cd biologically inactive for them; the ability to make this binding protein is heritable. The key heritable trait is the ability to make large amounts of the Cd-binding protein; worms making only 10% of this binding protein are not resistant and die of the toxic metal. [As the research paper says, previous work had established that the death rate (and, conversely, survival rate) in response to toxic metal levels was a very heritable trait. Indeed, by measuring death rates and heritabilities, the researchers found that the evolution of Cd resistance in Foundry Cove might take place within only 1-4 generations of these worms.] All well and good that the resistant worms detoxify the sediment by internally storing the Cd, but the bound metal moves through and up the aquatic food chain.

Superfund Remedial Actions Get Cadmium Back to Acceptable Levels

Some 15 years later, in 1994-1995, the Superfund Cleanup took place at the Cove. At that time Cd concentrations in the sediment were still markedly elevated at 2,000 parts per million (ppm), and the worms were still resistant compared to those in nearby unpolluted South Cove. Samples taken after the cleanup in 1996 showed that Cd levels were down to less than 10 ppm in the sediment.

The Worm Population Gradually Adapts to the Remediated Environment
One year after the cleanup, Foundry Cove worms were still genetically Cd-resistant even though the Cd levels were now about equal in the two coves. By 2001, Cd levels in both coves were down to less than 6 ppm, but resistance to Cd still persisted in Foundry Cove worms. Resistance to Cd steadily declined, and by the summer of 2002 the worms of Foundry Cove were no more resistant than those of South Cove. On the basis of reproductivity and sexual maturation, it took the worm population between 9 and 18 generations to completely disinherit their ability to be resistant to Cd, “which is a little more than three to four times the estimated time that it took to evolve resistance in the first place.” (The resistant worms did grow and reproduce, but they grew more slowly, possibly because they diverted energy from growth to producing the binding protein.)

Broad Scientific and Practical Significance of the Adaptability of Foundry Cove Worms
These worms are an excellent and rapid bio-assay for the process of recovery of any aquatic ecosystem from toxic metal pollution. The paper finishes with a remark relating back to the use of DDT: “In the case of Foundry Cove, nearly 100 million dollars was spent on the cleanup. Our study shows that environmental restorations may cause rapid genetic recoveries. Our results are consistent with a rapid recovery in resistance previously found when the use of the insecticide DDT was relaxed against the mosquito, Aedes aegypti.”