Date of Award

Summer 8-4-2022

Degree Type

Thesis

Degree Name

Master of Science in Integrative Biology (MSIB)

Department

Biology

Major Professor

Dr. Thomas McElroy

First Committee Member

Dr. Troy Mutchler

Second Committee Member

Dr. Allen Roberts

Third Committee Member

Dr. Kady Lyons

Abstract

Estuaries are transitional environments that play key roles in coastal ecosystem functioning by providing essential habitats to ecologically important plant and animal species. Estuaries are exposed to a number of anthropogenic impacts, including heavy metal contamination from human activities. However, few studies have examined heavy metal distribution within Georgia’s estuaries and how intact salt marsh ecosystems could play a role in filtering and sequestering contaminants, such as Mercury (Hg). This thesis examined blood total mercury (THg) concentrations of four coastal shark species and concentrations of five heavy metals (Hg, As, Cr, Cu, and Pb) within the water and sediments of three Georgia estuaries with varying levels of anthropogenic impact (Wassaw Sound-high impact, Ossabaw Sound-medium impact, and Doboy Sound-low impact). Contrary to predictions, Bonnethead (Sphyrna tiburo) showed no differences in their blood THg concentrations among estuaries (p = 0.115). However, there were species-specific differences, with THg concentrations in Atlantic Sharpnose (Rhizoprionodon terraenovae) being significantly higher (85.66 ± 192.49 ppb) than Blacktip (Carcharhinus limbatus; 13 ± 18.02 ppb), Bonnethead (12.84 ± 34.42 ppb), and Sandbar (Carcharhinus plumbeus; 12.77 ± 15.44 ppb; p = 0.003). The concentrations of water and sediment heavy metals were similar among the three estuaries (p ≥ 0.074), except for arsenic (As), where it was significantly higher in water samples from Doboy Sound with a mean concentration of 2669.17 ng/L (60.3% higher than Wassaw Sound and 75.1% higher than Ossabaw Sound) (p < 0.001). This data helps fill gaps in the literature regarding the effectiveness of THg as an indicator of local contamination, where other factors, such as diet, length, and migratory behavior appear to play larger roles in the accumulation of THg within shark blood.

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