Potential Anthropogenic Pressure on Six Selachii Species in Coastal Southeast Florida

Author

• Robert C. Foore, Halmos College of Arts & Sciences, Nova Southeastern UniversityFollow

Defense Date

7-27-2026

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Dr. Derek Burkholder

Second Advisor

Dr. Amy Hirons

Third Advisor

Dr. Dimitri Giarikos

Keywords

Selachii sharks, fin tissue, trophic niche, trace elements, Florida

Abstract

Trace element (TE) contamination is an understudied stressor to shark populations already affected by anthropogenic pressures. This study examined trophic ecology and TE accumulation in dorsal fin tissues from 58 individuals representing six shark species collected off southeast Florida between 2015 and 2025. Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes were analyzed using isotope ratio mass spectrometry, and 17 TEs were quantified using inductively coupled plasma–mass spectrometry. Mean δ¹⁵N values differed by 2.32‰ among species (10.97–13.3‰), less than the enrichment typically associated with a complete trophic-level shift, whereas δ¹³C variation indicated differences in carbon-source pathways and habitat use. Isotopic niche area varied more than fourfold, from 2.60 ‰² in sandbar sharks to 10.84‰² in great hammerhead sharks. Both sharks exhibited the highest geometric mean concentrations for 15 of 17 elements. Chromium reached geometric means of 6.19–17.3 µg/g and tin 0.304–0.709 µg/g, exceeding previously reported concentrations, while Hg reached up to 4.00 µg/g, both higher than previously reported averages. Concentrations of Al, Cr, Mg, Mo, Ni, Se, Sn, and Zn exceeded previously reported values for one or more shark species. This study also provides some of the first fin-specific concentration data for Al, Co, Fe, Mg, Mo, and Sn. Overall, TE accumulation was not explained by isotopic niche width alone, emphasizing the importance of integrating trophic ecology and contaminant monitoring in highly mobile marine predators.

Comments

Research conducted with Florida Fish and Wildlife Conservation Commission (FWC) special activity license (SAL-1505-SRP).

NSUWorks Citation

Robert C. Foore. 2026. Potential Anthropogenic Pressure on Six Selachii Species in Coastal Southeast Florida. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (242)
https://nsuworks.nova.edu/hcas_etd_all/242.