Habitat Specific Growth Rate Adaptation in Oysters During Early Bartonian: Effects of High Temperature and Low Seasonality in the Indian Palaeotropics
Mitra, A.; de Winter, N.J.; Miloikovitch, T.; Halder, K.; Ledesert, B.A.; Claeys, P.; Mueller, I.A. (2025). Habitat Specific Growth Rate Adaptation in Oysters During Early Bartonian: Effects of High Temperature and Low Seasonality in the Indian Palaeotropics. Paleoceanography and Paleoclimatology 40(10): e2025PA005129. https://dx.doi.org/10.1029/2025PA005129
In: Paleoceanography and Paleoclimatology. American Geophysical Union: Washington DC. ISSN 2572-4525; e-ISSN 2572-4525, more
|  |
| Author keywords |
Eocene;palaeoseasonality during MECO;palaeotropics of India;clumped isotope thermometry;palaeoclimate reconstruction;fossil oyster;eocene climatic optimum;low-mg calcite;isotope analysis;carbon-cycle;sr/ca ratios;shells;oxygen;mg/ca;kutch;paleogene |
| Authors | | Top |
- Mitra, A.
- de Winter, N.J., more
- Miloikovitch, T.
- Halder, K.
|
- Ledesert, B.A.
- Claeys, P., more
- Mueller, I.A.
|
|
| Abstract |
Seasonally resolved palaeoclimate reconstructions of extreme climatic events, coupled with responses of contemporaneous organisms, offer valuable information for mitigating the future. The tropical position of the Indian subcontinent during the Middle Eocene Climatic Optimum (MECO similar to 41 Ma), interrupting a general cooling trend, provides an ideal setting to investigate low-latitude seasonality under hot climate conditions, considering the modern minimal seasonality in the tropics. To better understand the seasonality and its impact on shallow marine fauna, a high-resolution multiproxy study is conducted on oyster specimens of the species Flemingostrea pseudoflemingi from the early Bartonian palaeo-tropical Kutch Basin. Clumped isotope (Delta(47)) thermometry combined with delta O-18 analyses from excellently preserved shell specimens suggest low seasonal temperature fluctuations (similar to 3 degrees C) with a mean temperature of 34.4 +/- 2.0 degrees C (95% CI) in the warmer season and 31.4 +/- 2.4 degrees C in the months of highest rainfall. Oyster populations from distinct regions within the basin display varying sizes. Smaller variants, inhabiting a zone influenced by marine conditions (delta O-18(w): -0.2 +/- 0.5 parts per thousand to 0.4 +/- 1.0 parts per thousand) experienced slower growth rates (similar to 18 mu m/day) only during the warmer months. In contrast, larger variants, probably residing in a shallower environment prone to larger impact of evaporation and fluvial influence (delta O-18(w): -1.0 +/- 0.8 parts per thousand to 1.0 +/- 0.7 parts per thousand), maintained a steady growth rate (similar to 58 mu m/day) throughout the year. Although the observed low seasonality is similar to modern tropical settings of the Indian and Pacific Oceans, the significantly warmer temperature range necessitated growth adaptations in oyster populations, as nutrient availability in diverse habitats were critical to their growth. |
|
