Document Type
Student Conference
Semester of Graduation
Spring 2026
Abstract
Coastal sharks have high concentrations of mercury (Hg) in tissues, but what increases mercury exposure is unclear. Blacktip (Carcharhinus limbatus) and bull (Carcharhinus leucas) sharks are commonly harvested in Louisiana’s commercial shark fishery. Because of health risk from mercury consumption, we ask: Are there food web characteristics that increase exposure of sharks to mercury? Biomarkers, such as stable isotopes sulfur (δ³⁴S) and nitrogen (δ¹⁵N) indicate feeding habits linked to prey trophic level and prey use of freshwater which influences total mercury (THg) concentrations. We hypothesize increasing trophic level (higher δ¹⁵N) and increasing reliance on freshwater prey (higher δ³⁴S) will increase exposure to THg. 36 bull sharks (female, n = 21; male, n = 15), and blacktip sharks (female, n = 25) were sampled. Bull sharks were 853.4 mm ± 289.2 mm s.d. fork length (FL) (female, 852.4 ± 249.3 mm; male 854.5 ± 237.1 mm), blacktip sharks were 1255.4 mm ± 117.1 mm. Using a Direct Mercury Analyzer (DMA-80) bull sharks had an average 0.8 parts per million (ppm) ± 0.7 ppm THg in muscle and 0.7ppm ± 0.5 ppm THg in liver samples and Blacktips averaged 2.4 ppm ± 10.5ppm THg in muscles and 2.6ppm ± 1.4 ppm THg in liver. The Stable Isotope Core Lab at Washington State University will analyze for sulfur (δ³⁴S) and nitrogen (δ¹⁵N) biomarkers. Finding a link between shark feeding ecology and mercury content can be a useful indicator for informing public health and safety.
Recommended Citation
Miller, M., Plumlee, J., Henderson, O., Moyo, S., & Hayes, M. (2026). Deriving Mercury Exposure Risk from the Feeding Ecology of Coastal Sharks in Coastal Louisiana. Retrieved from https://repository.lsu.edu/discover_dur/20
Awardee Name
Mallory Miller
Academic Major
Natural Resource Ecology & Management
Project Mentor
Jeffrey Plumlee