A new Li/Mg paleothermometer from pteropod shells

Scientific Reports, vol. 16

Abstract

Pteropods are promising proxy archives for paleoceanographic reconstructions but remain underexplored. Previous oxygen isotope analyses indicated that Heliconoides inflatus calcifies at shallow depths (50-75 m), suggesting its potential to record surface-ocean conditions. Here, we evaluate for the first time the applicability of Li/Mg thermometry in pteropod shells, a temperature proxy widely used in coral studies. We show that, in addition to recording environmental variability through shell carbon and oxygen isotopic composition, H. inflatus shells record upper-water temperature conditions, with Li/Mg ratios showing a robust relationship with ambient temperatures at sampling locations. Li/Mg ratios decrease exponentially with increasing temperature, enabling temperature reconstructions with an average precision of ± 1-2 °C. Pteropod shells (species H. inflatus, formerly known as Limacina inflata) were collected along a latitudinal transect in the Atlantic Ocean (31° N to 38° S), spanning a surface-water temperature gradient of approximately 15 °C. The global distribution and abundance of this annual species in sediments makes it a suitable alternative for paleo-surface temperature reconstruction. The utility of pteropod shells extends further to seasonal paleotemperature reconstruction, as seasonal temperature variability is captured in the elemental ratios from the embryonic to later (adult) sections of the shell. These results, in combination with a basin-scale distribution, make the Li/Mg thermometer in pteropods an exciting new tool in paleoceanography and further cement this group as new proxy archives.

Authors 5

1. N. Keul

   Christian-Albrechts-Universität zu Kiel

   Affiliation as printed

   Institute of Geosciences, Christian-Albrechts-Universität zu Kiel, Ludewig-Meyn-Str.10, 24118, Kiel, Germany. nina.keul@ifg.uni-kiel.de

2. D. Garbe-Schönberg

   Christian-Albrechts-Universität zu Kiel

   Affiliation as printed

   Institute of Geosciences, Christian-Albrechts-Universität zu Kiel, Ludewig-Meyn-Str.10, 24118, Kiel, Germany

3. V. Kitidis

   Plymouth Marine Laboratory

   Affiliation as printed

   Plymouth Marine Laboratory, Plymouth, UK

4. Gerald Langer

   Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

   Affiliation as printed

   Alfred Wegener Institute, Am Handelshafen 12, 27570, Bremerhaven, Germany

5. K.T.C.A.; id_orcid 0000-0001-7544-1079 Peijnenburg Aachen Naturalis Biodiversity Center

   Naturalis Biodiversity Center · University of Amsterdam

   Affiliation as printed

   Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, P.O. Box 94248, 1090 GE, Amsterdam, The Netherlands

   Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA, Leiden, The Netherlands