HR: 0800h
AN: B31D-0610    [Abstracts]
TI: Growth patterns of an intertidal gastropod as revealed by oxygen isotope analysis
AU: * Bean, J R
EM: bean@geology.ucdavis.edu
AF: Department of Geology, University of California at Davis, One Shields Avenue, Davis, CA 95616, United States
AU: * Bean, J R
EM: bean@geology.ucdavis.edu
AF: Center for Population Biology, University of California at Davis, One Shields Avenue, Davis, CA 95616, United States
AU: Hill, T M
EM: tmhill@ucdavis.edu
AF: Department of Geology, University of California at Davis, One Shields Avenue, Davis, CA 95616, United States
AU: Hill, T M
EM: tmhill@ucdavis.edu
AF: Bodega Marine Laboratory, University of California at Davis, P.O. Box 247, Bodega Bay, CA 94923, United States
AU: Guerra, C
AF: Department of Earth and Environment, Mount Holyoke College, 50 College Street, South Hadley, MA 01075, United States
AB: The size and morphology of mollusk shells are affected by environmental conditions. As a result, it is difficult to assess growth rate, population age structure, shell morphologies associated with ontogenetic stages, and to compare life history patterns across various environments. Oxygen isotope analysis is a useful tool for estimating minimum ages and growth rates of calcium carbonate secreting organisms. Calcite shell material from members of two northern California populations of the intertidal muricid gastropod Acanthinucella spirata was sampled for isotopic analysis. Individual shells were sampled from apex to margin, thus providing a sequential record of juvenile and adult growth. A. spirata were collected from a sheltered habitat in Tomales Bay and from an exposed reef in Bolinas. Abiotic factors, such as temperature, wave exposure, and substrate consistency, and biotic composition differ significantly between these sites, possibly resulting in local adaptations and variation in life history and growth patterns. Shell morphology of A. spirata changes with age as internal shell margin thickenings of denticle rows associated with external growth bands are irregularly accreted. It is not known when, either seasonally and/or ontogentically, these thickenings and bands form or whether inter or intra-populational variation exists. Preliminary results demonstrate the seasonal oxygen isotopic variability present at the two coastal sites, indicating 5-6 degC changes from winter to summertime temperatures; these data are consistent with local intertidal temperature records. Analysis of the seasonal patterns indicate that: 1) differences in growth rate and seasonal growth patterns at different ontogenetic stages within populations, and 2) differences in growth patterns and possibly age structure between the two A. spirata populations. These findings indicate that isotopic analyses, in addition to field observations and morphological measurements, are necessary to assess life history strategies and compare population dynamics under varying environmental conditions.
DE: 0419 Biomineralization
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0459 Macro- and micropaleontology (3030, 4944)
DE: 4858 Population dynamics and ecology
DE: 4870 Stable isotopes (0454, 1041)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting