Spatiotemporal stability of trace and minor elemental signatures in early larval shell of the northern quahog (hard clam) Mercenaria mercenaria.

摘要

The potential of trace and minor elements within biominerals to track the larval dispersal of bivalves was investigated by examining elemental composition in early larval shell of the northern quahog (hard clam) Mercenaria mercenaria. Larvae were cultured in three shellfish hatcheries using the adjacent estuarine waters of the southern Delmarva Peninsula in Virginia. Spatial distinction (~1-50 km) and temporal stability (triweekly) of elemental concentrations was assessed using inductively coupled plasma mass spectrometry. Seventeen minor and trace elements were present at detectable levels in all shell samples: Ca, Mg, Ti, Co, Ni, Zn, Se, Rb, Al, V, Cr, Mn, Cu, Sr, Ba, Pb, and U. Discriminant function analyses using metal-to-Ca ratios as independent variables assigned hard clams to their hatchery of origin correctly, with 100% success. The ratio Cr:Ca proved to be the most effective discriminator, explaining 78.1% of among-group variance. Elemental concentrations within early larval shell also differed temporally. Discriminant function analysis classified individual spawning events with 100% success, with Al:Ca explaining the bulk of among-group variance (81.4%). Despite temporal variability of elements within larval shell, it was possible to resolve elemental signals spatially among hatcheries regardless of spawning date. These results demonstrate for the first time that the chemical composition of hard clam larval shell records spatial elemental signatures with the potential to trace the environment of natal origin as well as subsequent dispersal trajectories of this economically important species.