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Scholarly Works (2 results)

  • Article
Coastal Environmental Quality Initiative (2005)

One of the least understood and most fundamental processes in marine ecology is dispersal, or transport of larvae. To what extent are local adult population dynamics influenced by the dispersal of larvae from neighboring source populations? Do self-recruiting populations exist? How far do larvae disperse? The sources and destinations of larvae have been unknown for nearly all commercially important species, yet any model of resource management or biodiversity preservation depends on this information. We wish to understand the interdependency of commercially important California coastal populations by identifying the sources of larval recruits. To do this, we will use environmental signatures, consisting of trace metal inclusions in the hard structures of larvae (e.g., fish otoliths) that are laid down over time. Elements from the surrounding seawater become permanently incorporated into the structures, which then act as daily recorders of the environment experienced during the larval phase. Along coastal margins, concentrations of many trace elements are significantly higher than in the open ocean, and differences in trace element concentrations among coastal water masses occur as well. Recently developed high-precision mass spectrometers and laser microprobes allow a sequential analysis of past environments, down to a resolution of a few days.

We propose the following interrelated approaches to the problem of reconstructing larval paths:

• Validation: How well and how consistently is water chemistry reflected in the trace element composition of hard parts produced by organisms? Can the techniques be extended to other commercially important species?

• Documenting the temporal and spatial nature of environmental signatures: constructing an “atlas” of potential source populations.

• Tracing larval sources through microchemical analyses of new recruits by matching core signatures of hard parts to the “atlas”, and through a pilot mark-recapture study.

• Integrating the results into ongoing students of population genetics and ocean circulation models.

    Cover page: Larval Pathways and Population Connectivity in Nearshore Marine Organisms
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2009)
    Despite the interest in restoring remnant populations of the Olympia oyster, Ostrea lurida Carpenter 1864,† little is known about connectivity among populations. Identifying the sources of settling larvae could broaden our understanding of the degree to which particular populations are reliant on their neighbors for their persistence. Calcified structures such as the otoliths of fish and statoliths of invertebrates are increasingly being exploited as useful "natural tags" that help track individual movements and, when applicable to larvae, could help to pinpoint important source populations. In controlled laboratory culturing experiments, we explored the prospects for using the chemistry of larval shells (prodissoconchs) as natural tags of larval source by examining whether larval shells record shifts in seawater element chemistry, whether larval shells undergo ontogenetic shifts in element uptake, and whether the chemistry of the shell formed during brooding is compromised by subsequent shell thickening during the planktonic phase. Results from a two-way ANOVA examining the effect of seawater element concentration and ontogeny showed that element/ Ca in the shell increased in response to increasing seawater elemental concentrations for Ba, Ce, Pb, and Mn, whereas shell Cu/Ca did not change. Ostrea lurida shell chemistry also showed strong ontogenetic shifts in element/Ca for Mg, Sr, and Cu during the transition from larva to settler. Settler shell Mg/Ca strongly increased compared with planktonic shell, whereas Sr/Ca and Cu/Ca showed the opposite pattern. Further, the chemistry of the shell formed during brooding (at the birth location) did change as a function of environmental conditions experienced during the planktonic phase for the elements Ba and Ce, but that change was limited to regions of the brooded shell just adjacent to the planktonic shell. When the brooded portions of larval shells were sampled closer to the umbo, the brooded shells' chemistry remains intact. The combined results suggest that larval Ostrea lurida shells act as recorders of environmental change and show promise as tools to track larval movements.
      Cover page: A Shell of Its Former Self: Can Ostrea lurida Carpenter 1864 Larval Shells Reveal Information About a Recruit's Birth Location?
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