Aging in Remote Waters: How Are Hawaiian Monk Seal Teeth Documenting Environmental Impacts?

Aging in Remote Waters: How Are Hawaiian Monk Seal Teeth Documenting Environmental Impacts?

Alvin Sherman Library

The Hawaiian Monk Seal (HMS) is the second most endangered pinniped species, and an apex predator endemic to the Hawaiian Archipelago. Majority of the population resides in the Northwest Hawaiian Islands which are divided into three regions for research purposes: Northern Hawaiian Island (NHI), Central Hawaiian Island (CHI), and Southern Hawaiian Island (SHI). This study analyzed long-term trace elements (TE) exposure in HMS by measuring 17 TEs (Ca, Cd, Co, Cr, Cu, Ba, Fe, Li, Mg, Mn, Mo, Ni, Pb, Sn, Sr, V, Zn) in cementum growth layer groupings (GLGs) of canine teeth using laser ablation induced coupled plasma mass spectrometry. Cementum accretes annually in distinct GLGs, with paired light and dark layers representing one year of life. Sampled individuals spanned ages 9-28 years across regions, representing a time frame of 1964 to 2011. Analysis of TE concentrations relative to age and region provides insight into historical environmental conditions and potential anthropogenic influences on TE accumulation. Across all samples, the highest TE concentrations were observed as follows: Ca (338927.72-1344291.72 mu;g/g) > Mg (12196.84-57890.36 μg/g) > Sr (501.35-4146.21 μg/g) > Zn (262.98-2053.51 μg/g) > Ba (5.71-103.55 μg/g). Consistent rations between Ba/Ca, Sr/Ca, and Zn/Ca were also observed in correlation with other pinniped teeth. Regional differences were evident, with the SHI displaying a decline in Pb in the late 1970s, potentially reflecting changes in commercial fuel composition and reduced foreign fishing activity following the 1976 Fisheries Conservation and Management Act. In contrast, CHI individuals exhibited higher variability (>50%) in several TE concentrations, suggesting greater individual-level differences in diet and foraging behavior. Overall, this study demonstrates the use of cementum GLGs for reconstructing historical TE exposure, and insights into ecosystem health, supporting conservation and management of pinniped populations within the Hawaiian Archipelago.