- 1School of Ocean and Earth Science, University of Southampton, Southampton, UK
- 2Climate Geochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
- 3Department of Earth and Planetary Sciences, ETH Zurich, Zurich, Switzerland
Nitrogen isotopic composition (δ¹⁵N) measured on organic matter within biominerals (fossil-bound) is an emerging proxy for reconstructing marine trophic conditions in deep time. While previously applied to foraminifera, diatoms, corals, shark teeth, and fish otoliths, the application of δ¹⁵N to other shallow-water marine taxa has been relatively limited. To evaluate the potential of sea urchins as a new model for paleoenvironmental and paleoecological reconstructions, we herein investigate fossil-bound δ¹⁵N in modern and fossil sea urchin biominerals and, for extant samples, its relationship to tissue δ¹⁵N.
Our findings indicate a δ¹⁵N difference of up to 3 ‰ between plates and spines within an individual sea urchin, with an observed nitrogen isotope gradient from the aboral surface to oral surface in both test plates and spines. In addition, we directly compare the δ¹⁵N signature of the gonads, gut content and body wall tissue with the biomineral-bound δ¹⁵N of the teeth, hemipyramids, rotulae, compasses, perignathic girdle, plates and spines. We suggest that biomineral-bound δ¹⁵N preserves trophic signals while also capturing internal isotopic gradients.
Extending this method, we analysed δ¹⁵N in various echinoid genera from the Carboniferous (Mississippian and Pennsylvanian) across multiple localities spanning the globe as a means of understanding their, previously poorly-defined, role in Paleozoic ecosystems. This study is a first step towards the application of fossil-bound nitrogen isotopes to this diverse group, providing new insights into trophic conditions and ecological structures in Paleozoic marine benthic ecosystems.
How to cite: Auderset, A., Bieler, A. L., Martínez-García, A., and Thompson, J. R.: Exploring Fossil-Bound Nitrogen Isotopes in Modern and Paleozoic Sea Urchins: A New Window into Benthic Ecosystems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15935, https://doi.org/10.5194/egusphere-egu25-15935, 2025.