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Micro-Raman spectroscopy has been used on adult bivalve shells to investigate organic and inorganic shell components but has not yet been applied to bivalve larvae. It is known that the organic matrix of larval shells contains pigments, but less is known about the presence or source of these molecules in larvae. We investigated Raman spectra of seven species of bivalve larvae to assess the types of pigments present in shells of each species and how the ratio of inorganic : organic material changes in a dorso-ventral direction. In laboratory experiments, we reared larvae of three clam species in waters containing different organic signatures to determine if larvae incorporated compounds from source waters into their shells. We found differences in spectra and pigments between most species but found less intraspecific differences. A neural network classifier for Raman spectra classified five out of seven species with greater than 85% accuracy. There were slight differences between the amount and type of pigment present along the shell, with the prodissoconch I and shell margin areas being the most variable. Raman spectra of 1-day-old larvae were found to be differentiable when larvae were reared in waters with different organic signatures. With micro-Raman spectroscopy, it may be possible to identify some unknown species in the wild and trace their natal origins, which could enhance identification accuracy of bivalve larvae and ultimately aid management and restoration efforts.

The land–sea interface, or Coastal Transition Zone (CTZ), is the area that links terrestrial and marine habitats. We use here the definition of [Schaefer, 1972]: “the sea and the land adjacent to the interface, encompassing that region where terrestrial activities importantly impinge on the marine environment, marine resources and marine activities, and where marine activities importantly impinge on the environment, resources, and activities of the land”. The precise spatial scale and extent of the interface in this definition is (appropriately, we feel) ambiguous, as it depends on both the attributes of the interface at any given location, as well as the processes or features being examined. Like many ecotones, the CTZ is an area of intense interactions and enhanced productivity and biodiversity ([Levin et al., 2001]). The coastal zone is also a “keystone” habitat, providing human and ecosystem services out of proportion to its areal extent (e.g., [Costanza et al., 1997]). The coastal zone represents only 8% of the earth, but provides 20% of the oceanic production ( [Liu et al., 2000. K.K. Liu, K. Iseki and S.Y. Chao, Continental margin carbon fluxes. In: R.B. Hanson, H.W. Ducklow and J.G. Field, Editors, The Changing Ocean Carbon Cycle, Cambridge (2000), pp. 187–239.Liu et al., 2000]). Further, 60% of humans, 3.8 billion people, live within 100 kilometers of the sea ( [Vitousek et al., 1997]). This region is a nexus for transportation, production of energy, and food resources for humans. The importance of this region, both to humans and to terrestrial and aquatic ecosystems, makes it crucial that we understand the processes and interactions in this habitat. The coastal transition zone, however, presents a number of difficult research challenges. While these challenges are qualitatively similar to those faced by scientists in other habitats, they are magnified in the coastal transition zone. The goal of this paper is to describe the difficulties that confront the r