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Oyster Contaminants

Full Title: Use of elemental signatures to detect and trace contaminant entry to the northern Gulf of Mexico coastal food web: Managing multiple stressors

This project is testing whether trace elements associated with oil can be detected in oyster shells and serve as an indicator of oil exposure thus providing resource managers with a way to detect past oil exposure on oyster reefs.

Kassey Trahanas, an intern with the project, cleaning an oyster.
Kassey Trahanas, an intern with the project, cleaning an oyster.

The Team: Ruth Carmichael (Lead Investigator, Dauphin Island Sea Lab, University of South Alabama,

Technical Monitor: Dennis Apeti (

Federal Program Officer/Point of Contact: Frank Parker (

This project began in June 2017 and will end in May 2021.

Award Amount: $231,671

Why it matters: Oysters can serve as a record of water conditions at a particular site because they are stationary filter feeders with a hard shell that incorporates elements from the surrounding water as it continually grows. By determining if trace elements associated with oil exposure are incorporated into a living oyster’s shell and under what conditions, the investigator will provide resource managers with an approach to detect when an oyster is exposed even after the oil is no longer present.

What the team is doing: This study will test whether current or past exposure to contaminants may have affected the status of restored oyster reefs in Alabama, Mississippi, and Louisiana. These experiments will make it possible to determine if the chemical fingerprint in oyster shell can be linked back to exposure of that oyster to a contaminant. Because oysters live in waters that vary in salinity, particularly on the Northern Gulf of Mexico coast, where freshwater discharge can be very high, this link will be tested under different salinities. Understanding this linkage will make it possible to use historical oyster shell and tissue samples to assess past contaminant exposure at different sites. The trace element profiles in the shell of oysters exposed to contaminants will also be compared to measures of the biological condition of the oyster, such as growth rate, to relate the condition of oysters at a particular site following contaminant exposure. Using data on mortality and abundance at active oyster restoration sites, this project will also assess whether current or previous exposure to contaminants may be related to the status of a restored reef, where historical data are available.

Expected Outcome: Overall, the results of this work will benefit the recovery of oyster reefs and the economic and ecosystem services they provide by enhancing future biomonitoring efforts in the northern Gulf of Mexico and other locations where oysters grow. Applications could include guiding site selection for restoration or propagation and coastal land-use management. 

From the seminar “Eastern Oysters (Crassostrea Virginica) as Retrospective Bioindicators of Trace Metal Contamination” 
Presenter: Dr. Ruth Carmichael, Dauphin Island Sea Lab, University of South Alabama

Other Resources