NORFOLK, Va.--With a heavy-duty pump steadily providing the heartbeat for a recent research operation, the Engineer Research and Development Center's Toxicology Laboratory cradled 75 electronically-wired oysters in a first-of-its-kind experiment, testing the effects of various sediment levels supporting the Corps’ Norfolk District dredging operations.
Project Director Dr. Burton Suedel explained the experiment would provide data for the Norfolk District to address concerns brought by some state regulators and other stakeholders who contend the yearly dredging operations along portions of the James River resulted in sediment plumes that harm oysters where they occur, in areas of the river where fresh and salt water mix, providing living conditions essential for oyster reefs to thrive.
Funding for this research comes from the Dredging Operations and Environmental Research (DOER) program.
Assisting Suedel in this unique experiment, Barry Marcel of the University of Louisiana at Monroe (ULM) carefully weighed and measured the oysters gathered from the Chesapeake Bay watershed before they were attached to the electronic-monitoring system designed to measure and record how often the carefully-numbered oysters opened and closed their shells.
Half-way through his doctoral studies in toxicology, Marcel learned of this experiment when Suedel, an adjunct professor at ULM, shared the research opportunity with Dr. Kevin Baer, head of ULM’s Department of Toxicology. Marcel noted the outstanding benefits of the specially-designed EL laboratory and the professional benefits offered to graduate students who assist with EL research.
Unique laboratory system
The laboratory system used for this unique oyster monitoring, designed and built more than seven years ago by EL’s Charles Lutz, is known as the Fish Larvae and Egg Exposure System (FLEES).
According to Tech Note (DOER-E32), the FLEES exposes early life stages of fish and shellfish to specified concentrations and durations of suspended sediment in a controlled laboratory environment.
By using the FLEES, much needed data are developed to evaluate the effectiveness and necessity of environmental windows intended to protect the selected species. Environmental windows are periods during which dredging is allowed to proceed in a waterway. These time frames associated with dredging operations have become increasingly restricted, greatly limiting the amount of time available to dredge waterways. Dredging-related suspended sediment plumes are thought by some to adversely affect fish and other aquatic life. But data do not exist to help understand the effects of such plumes on sensitive early life stages of fish and shellfish used to set dredging windows.
“Last year we were studying walleye, and next year it will be sturgeon,” Suedel said, noting that this year’s oyster study is unusual because it was the first shellfish experiment conducted in the FLEES.
Matching oysters’ habitats
The experimental oysters were exposed to varying concentrations of suspended sediment from the James River up to 500 mg/L total suspended solids, with electronic monitors recording the opening and closing of each oyster shell, 24 hours a day during the seven-day experiment.
“A happy oyster has his shell open. But the relatively high concentrations of suspended sediments that we’re exposing the oysters to don’t allow you to view whether the shell is opened or closed. You can’t see further than a half-inch below the water surface. And that’s why the electronics are necessary to record their reactions to the various suspended sediment levels,” said Suedel. “Chillers kept the water temperature around 13 degrees Centigrade to mimic the James River water temperature in December. The same amount of salinity) found in the James River also circulated throughout the FLEES aquariums during the study.
“Our hypothesis is there will be no difference in oyster responses among the three suspended sediment levels,” Suedel said. He added the oyster sediment experiment results will be used to help the Norfolk District solve its dredging windows issues in the James River. The results of the study will be published in a scientific journal in 2013.
Expanding toxicology knowledge
Marcel related that oysters’ gills are designed to expel non-digestible materials from all they take in, including non-nutritious particles of sediment.
“Further studies may even reveal the oyster’s ability to detect predators and other coping mechanisms. These types of experiments allow us to expand our knowledge and reach in the world of toxicology. We can do a lot more work at this (ERDC) lab in expanding that knowledge. It really is a technical marvel. It takes a lot of pressure off how we are going to expose the oysters to the sediment and get valid results.”
“And we will continue to offer such research opportunities to graduates students,” said Suedel. “We are always striving to share knowledge and solve problems. Solving problems is what I like to do best.”