Analysis of trace transition elements and heavy metals in fish otoliths as tracers of habitat use by American eels in the Hudson River estuary

Transition and heavy metals within the calcified otoliths of estuarine fishes may represent valuable tracers of environmental exposures, allowing inferences on natality, habitat use, and exposure to pollution. Accurate measurement of very low concentrations of these metals in otoliths by inductively coupled plasma mass spectrometry (ICP-MS) is often precluded by the interferences of predominant calcium matrix. We coupled a solid phase extraction procedure to an ICP-MS instrument to overcome the matrix problems and improve the limits of detection. To test this novel application and the utility of otolith transition and heavy metals as tracers of habitat use, otoliths of American eel (Anguilla rostrata) captured from 6 locations (George Washington Bridge, Haverstraw, Newburgh, Kingston, Athens, and Albany) throughout the Hudson River estuary were analyzed for site specific differences expected due to varying environmental exposure. Several trace elements, including Al, Bi, Cd, Co, Cu, Ga, Mn, Ni, Pb, V, and Zn, were selectively extracted from otolith solutions and preconcentrated on a microcolumn of chelating resin. The concentrations of all elements inA. rostrata otoliths were above the limits of detection that ranged from 0.2 ng g^?1 for Co to 7 ng g^?1 for Zn. Differences in the elemental composition of the otoliths among the groups were significant indicating different levels of exposure to environmental conditions. Discriminant analysis yielded an overall location classification rate of 78%. Al, Bi, Cd, Mn, Ni, and V contributed most to the discriminant function. Samples collected at George Washington Bridge showed 100% discrimination from other locations, and higher levels of many transition and heavy metals, consistent with higher exposure to these metals in the most polluted region of the Hudson River estuary.