Bivalve dispersal as indicated by shell trace element composition

Lauren S. Mullineaux

For decades, researchers have been searching for a marker that will help identify the source habitat of larvae settling into a benthic population. Bivalve larvae spend up to 60 days in the planktonic state. During that time, the larvae can be transported great distances by coastal currents, making it difficult to determine the geographic origin of the larvae. Ultimately, these dispersal processes have an important impact on the magnitude and variation of recruitment.

Our laboratory is developing a marker for bivalves by focusing on trace-element incorporation by the larval shell, and by utilizing highly sensitive analytical facilities (ICP/MS and ion microprobe) available at WHOI. We are conducting laboratory experiments on bivalve larvae to determine whether the initial larval shell incorporates trace elements from its environment, and to evaluate whether the suite of elements in the larval shell provides a unique fingerprint that can be used as a marker of its source habitat.

Juvenile (approximately 2 mm) soft-shell clams, Mya arenaria. Photo by Lara Gulmann, WHOI.

Bivalve larvae incorporate distinctly elevated amounts of trace elements into their shells when they are spawned in water with elevated concentrations of those elements. Because the larval shell is retained as part of the juvenile shell, each bivalve carries a record of the trace element composition of its larval environment: a unique, location-specific fingerprint, of sorts. The trace element composition of water, and overlying sediments of coastal habitats, varies geographically along the coast.

To determine whether this variation translates into a useful marker in the bivalve shell, we are comparing field-collected individuals with those spawned in the laboratory under controlled trace element conditions. The resultant marker will give us a powerful and direct tool for tracking larval dispersal in coastal waters, and for understanding the interaction of hydrodynamics and behavior in the dispersal process.

This research was supported by the Rinehart Coastal Research Center at WHOI, the Office of Naval Research, and WHOI Sea Grant.

Previous Project | Next Project