Geographic and Oceanographic Information within Trace Metals in Moray Eel Otoliths

Adult moray eels exhibit high site fidelity to particular reefs. We hypothesized that the trace metal composition of otoliths of eels could potentially provide insight into gradients in oceanographic processes on the South Atlantic Bight continental shelf where eels are resident on patchy hardbottom reefs throughout the entire region. Otoliths of moray eels collected from the mid-shelf of South Carolina were examined for their trace metal composition (Ba, Sr, Pb, Cu, Li, Mg, V, Mn, Zn). Samples were broadly lumped into four regions: “North,” “North Cape Romain,” “South Cape Romain,” and “South”. Trace metal composition within otoliths showed no latitudinal trends. However, factor analysis of the trace metals revealed that otoliths from the South Cape Romain region appeared as a compositionally distinct subgroup, based primarily on their Li and Mg content. Recent work on corals (Montagna et al. 2014) has shown the Li/Mg ratio within coral skeletons is sensitive to calcification temperature and can be used as a paleothermometer. If analogous processes influence Li/Mg ratios within otoliths, the data suggest that the bottom water at the South Cape Romain site is colder than other locations along the South Carolina shelf, perhaps as a result of locally enhanced upwelling. Additional samples from NC, SC, GA, and FL are being examined to see if other sites within the South Atlantic Bight show similar patterns.

Montagna, P., McCulloch, M., Douville, E., et al. 2014. Li/Mg systematics in scleratinian corals: Calibration of the thermometer. Geochim Cosmochim Acta 132: 288-310.