Using Stable Isotopic Data to Resolve Rate and Duration of Growth throughout Ontogeny: An Example from the Surf Clam, Spisula solidissima

摘要

Examination of ontogenetic variation in the stable isotopic composition of accretionary biogenic hard parts is becoming a commonplace technique for gaining insights into organism age, changes in growth rate through ontogeny, and environmental conditions under which organisms lived. However, the application of isotopic data to life-history studies often is impeded by the noisy nature of environmental signals, as well as by seasonal cessation of hardpart accretion. A computational approach is presented that quantitatively resolves secular (seasonal) change in environmental parameters such as temperature and salinity with spatial (hard part) variation in isotopic composition. Output consists of determinations of mean annual isotopic composition, seasonal range in isotopic composition, and variation in hard-part growth rate for any interval of data in an accretionary transect. Quantitative estimates of absolute growth rates, as well as the proportion of each season represented by hard-part accretion, are derived for every season of the organism's life recorded in their hard parts.