Brachiopod shell is an important biogenic carbonate archive of seawater and ocean conditions for the last five hundred million years, and its accretionary nature and capacity to incorporate isotopes (δ13C and δ18O) has the potential to disclose the seasonality of past climates. To determine, if and how, these shells are reliable archives of seasonal variation of environmental conditions, we investigated external shell growth lines, and their underlying microstructure alongside δ13C and δ18O values of the shell in a modern New Zealand brachiopod, Calloria inconspicua. We describe the morphology of shell growth lines and their hierarchical arrangement during ontogeny, and employ Shell Spiral Deviation analysis to quantify periodic and aperiodic components of growth. Ontogenetic time series of δ13C and δ18O values for the secondary fibrous shell were measured and related to growth lines and spiral deviations, as well as to concurrent seasonal seawater isotope values. For C. inconspicua, seasonal growth rate of shell length changes during ontogeny. After an early phase, when individuals (SL < 15 mm) grow during all seasons, older brachiopods preferentially grow during the warm season with marked growth halts in the colder season. As a result, full seasonal variations are not completely recorded during the adult life stage. Additionally, it is evident from the δ13C values that there is some vital effect, which is most likely related to metabolic processes. Juvenile shell growth is continuous for the first two years post-settlement and records the full variation of δ18O values associated with seasonal changes in sea temperature. The juvenile shell of C. inconspicua is thus an archive for seasonality of seawater temperature and environmental δ18O variability, suggesting that fossil brachiopod shells can be used to reconstruct seasonality in the recent and deep past, by selecting the early growth phases.
Brachiopod shells as archives of seasonality. Insights from growth lines, microstructure, δ13C and δ18O values in Calloria inconspicua / Garbelli, Claudio; Lamare, Miles D.; Harper, Elizabeth M.. - In: MARINE BIOLOGY. - ISSN 0025-3162. - 172:7(2025). [10.1007/s00227-025-04675-8]
Brachiopod shells as archives of seasonality. Insights from growth lines, microstructure, δ13C and δ18O values in Calloria inconspicua
Garbelli, Claudio
;
2025
Abstract
Brachiopod shell is an important biogenic carbonate archive of seawater and ocean conditions for the last five hundred million years, and its accretionary nature and capacity to incorporate isotopes (δ13C and δ18O) has the potential to disclose the seasonality of past climates. To determine, if and how, these shells are reliable archives of seasonal variation of environmental conditions, we investigated external shell growth lines, and their underlying microstructure alongside δ13C and δ18O values of the shell in a modern New Zealand brachiopod, Calloria inconspicua. We describe the morphology of shell growth lines and their hierarchical arrangement during ontogeny, and employ Shell Spiral Deviation analysis to quantify periodic and aperiodic components of growth. Ontogenetic time series of δ13C and δ18O values for the secondary fibrous shell were measured and related to growth lines and spiral deviations, as well as to concurrent seasonal seawater isotope values. For C. inconspicua, seasonal growth rate of shell length changes during ontogeny. After an early phase, when individuals (SL < 15 mm) grow during all seasons, older brachiopods preferentially grow during the warm season with marked growth halts in the colder season. As a result, full seasonal variations are not completely recorded during the adult life stage. Additionally, it is evident from the δ13C values that there is some vital effect, which is most likely related to metabolic processes. Juvenile shell growth is continuous for the first two years post-settlement and records the full variation of δ18O values associated with seasonal changes in sea temperature. The juvenile shell of C. inconspicua is thus an archive for seasonality of seawater temperature and environmental δ18O variability, suggesting that fossil brachiopod shells can be used to reconstruct seasonality in the recent and deep past, by selecting the early growth phases.| File | Dimensione | Formato | |
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