Mother Nature can disrupt the best intentions of humans.
Peter McCall and Gerald Matisoff, geologists in the College of Arts and Sciences at Case Western Reserve University, and undergraduate researchers are studying how marine invertebrates disturb harbor dredgings, deposited and capped miles off shore to sequester polluted sediment.
The research project will focus on learning more about the feeding and burrowing habits of marine animals in mud-capped sediment which have the potential to return buried and polluted materials to harbors and shorelines and potentially disturb nearby marine ecology.
The Army Corps of Engineers oversees the maintenance of harbors along the seaboard, the Great Lakes and rivers. As part of harbor maintenance, it dredges harbors for navigation, removing sediment that has collected from river deposits or incoming tides. Dredge spoils are either put onshore, where pollutants may leach back into the water, or dumped 10 to 15 miles offshore on the continental shelf and covered with a thin 'cap' of clean uncontaminated sediment.
Professor McCall and co-investigator Matisoff, professor and chair of the department of geological sciences, have a three-year $155,000 grant from the U.S. Army Corps of Engineers to create a mathematical model of feeding and sedimentation to determine how thick a clean mud cap needs to be to protect dredged deposits.
This summer they are studying an ubiquitous burrowing worm, Heteromastus filiformis, a marine relative of the land-based earthworm. It tunnels and eats its way through the sequestered sediment, and in turn, mixes this material with the environment around it.
But it is not alone in making changes along the ocean floor. Other marine animals like crustacean shrimp and clams also contribute to the process of mixing sediments. These species will be studied, too, as part of the research project, because like the worms they are conveyor belt feeders, eating sediment at depth and depositing it like a conveyor belt at the sediment surface above the protected cap, said McCall.
This summer McCall and undergraduates Rita Cabral and Laura Mulvey will visit sites on Cape Cod and New Hampshire to collect marine worms and bring specimens back to McCall's and Matisoff's laboratory in the A.W. Smith Building on campus to study the worms in varied lab environments. Their lab is one of two or three in the country equipped to study the movement of sediment by deposit-feeders in the required detail.
They will place radioactive cesium tracers in the sediment to track how the worms move the sediment at different depth levels and how deep and how fast their study organisms disturb the sediment. Once the model is created, they will share the information with Army Corps to help them plan and maintain future dredging.
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