Bivalve shell-based, high-resolution multi-proxy reconstruction of marine primary production – Pecten maximus, Bay of Brest

• Applicant: Professor Dr. Bernd R. Schöne
• Subject Area: Palaeontology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions ; Oceanography
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 406350147

• Final Report Year: 2024

Final Report Abstract

This German-French cooperation project HIPPO (HIgh-resolution Primary Production multi-prOxy archives) aimed to develop and refine geochemical proxies to reconstruct changes of marine primary production from bivalve shells. Primary production proxies provide valuable tools for marine scientists, paleoecologists and paleoclimatologists. The Bay of Brest in NW France was chosen because of its well-studied ecosystem. The main focus was placed on element chemical impurities (Ba, Mo, Li) in the shell of Pecten maximus, measured by Laser Ablation – Inductively Coupled Plasma – mass spectrometry (LA-ICP-MS). By comparison with a comprehensive environmental monitoring data set of the biological and physicochemical properties of the water (= French part), Ba/Cashell, Mo/Cashell and Li/Cashell were assessed as phytoplankton proxies. The main findings of this project were as follows: 1) Ba/Cashell is indicative of specific phytoplankton species, in particular diatoms, but does not serve as a surrogate for the abundance of phytoplankton at large. 2) Species-specific differences in the amount of Ba within phytoplankton cells need to be considered when interpreting Ba/Cashell profiles. 3) Mo/Cashell is associated with blooms of specific dinoflagellates and diatom aggregation events. 4) Large diatom blooms and the abundance of a specific genus of toxin-producing diatom induce the formation of Li/Cashell peaks. 5) A time lag of a few days exists between the phytoplankton bloom and the element/Ca increase in the shell. 6) Ba/Cashell, Mo/Cashell and Li/Cashell ratios record changes in primary production in the water column rather than processes at the sediment-water interface (SWI). 7) Ba/Cashell, Mo/Cashell and Li/Cashell profiles can serve as qualitative and quantitative proxies to reconstruct phytoplankton dynamics, but the latter requires normalization because specimen-specific physiological parameters (shell height, growth rates and filtration rates) influence the trace element uptake and incorporation into the shell. 8) Analyses of archaeological P. maximus shells revealed that environmental signals of the last ca. 4500 years are reliably recorded and preserved within the shell carbonate allowing to reconstruct past phytoplankton dynamics. 9) Nitrogen isotopes of the carbonate-bound organic matrix (CBOM) measured via BSIA (bulk stable isotope analysis) as well as CSIA (compound-specific stable isotope analysis, CSIA; specifically: amino acids) suggest that scallop shells serve as highresolution archives of food web dynamics. The results and hypotheses obtained and developed in this project lay the foundation for future studies. (1) Controlled feeding experiments using specific phytoplankton species as food sources would be extremely useful to validate the proposed uptake mechanisms of P. maximus and to fine-tune such proxies. (2) To reveal the full potential of Ba/Cashell Mo/Cashell and Li/Cashell as high-resolution proxies for primary production, sclerochronologists should test these geochemical tracers in other scallop taxa and other bivalve species. (3) Subsequent work should continue examining (sub)fossil shells using the geochemical tools developed herein, in order to study the anthropogenic influence on phytoplankton dynamics and facilitate predictions of future primary production.

Publications

• Scallop shells as geochemical archives of phytoplankton‐related ecological processes in a temperate coastal ecosystem. Limnology and Oceanography, 67(1), 187-202.
  Thébault, Julien; Jolivet, Aurélie; Waeles, Matthieu; Tabouret, Hélène; Sabarot, Sophie; Pécheyran, Christophe; Leynaert, Aude; Jochum, Klaus Peter; Schöne, Bernd R.; Fröhlich, Lukas; Siebert, Valentin; Amice, Erwan & Chauvaud, Laurent
  
• Ba/Ca profiles in shells of Pecten maximus – A proxy for specific primary producers rather than bulk phytoplankton. Chemical Geology, 593, 120743.
  Fröhlich, Lukas; Siebert, Valentin; Walliser, Eric O.; Thébault, Julien; Jochum, Klaus Peter; Chauvaud, Laurent & Schöne, Bernd R.
  
• Deciphering the potential of Ba/Ca, Mo/Ca and Li/Ca profiles in the bivalve shell Pecten maximus as proxies for the reconstruction of phytoplankton dynamics. Ecological Indicators, 141, 109121.
  Fröhlich, Lukas; Siebert, Valentin; Huang, Qian; Thébault, Julien; Jochum, Klaus Peter & Schöne, Bernd R.
  
• HIPPO environmental monitoring: Impact of phytoplankton dynamics on water column chemistry and the sclerochronology of the king scallop (Pecten maximus) as a biogenic archive for past primary production reconstructions.
  Siebert, Valentin; Moriceau, Brivaëla; Fröhlich, Lukas; Schöne, Bernd R.; Amice, Erwan; Beker, Beatriz; Bihannic, Kevin; Bihannic, Isabelle; Delebecq, Gaspard; Devesa, Jérémy; Gallinari, Morgane; Germain, Yoan; Grossteffan, Émilie; Jochum, Klaus Peter; Le Bec, Thierry; Le Goff, Manon; Liorzou, Céline; Leynaert, Aude; Marec, Claudie ... & Thébault, Julien
  
• Uptake of barium, molybdenum, and lithium and incorporation into scallop shells: Refining proxies for primary production dynamics. Limnology and Oceanography, 68(11), 2544-2561.
  Fröhlich, Lukas; Siebert, Valentin; Huang, Qian; Thébault, Julien; Moriceau, Brivaëla; Jochum, Klaus Peter & Schöne, Bernd R.