Muschelschalen-Mikrostrukturen - ein neuartiger Proxy für Meerestemperaturen
Zusammenfassung der Projektergebnisse
The goal of this project was to explore the potential of bivalve shell microstructures as an emerging paleotemperature proxy. For this purpose, we analyzed the size and shape of individual biomineral units (BMUs) of field-collected and lab-raised specimens by means of SEM and semi-automated image processing methods employing artificial intelligence. Morphological data were compared to temperature, salinity and chlorophyll a data of the waters in which the bivalves lived. The main results of this project were as follows: (1) Temperature has a consistent effect on the size of shell BMUs across species and microstructure boundaries as long as the bivalves are not stressed. This was demonstrated for Arctica islandica and Glycymeris spp. (2) Microstructure properties change during ontogeny, likely as the result of variations in overall growth rate and/or energy allocation. To employ shell microstructure properties as a proxy for temperature, ontogenetic effects need to be mathematically eliminated. Alternatively, only BMUs of the same stage of life from specimens with similar growth rates should be used. (3) The shell microstructure is not exclusively influenced by temperature. Stressful environmental conditions negatively affect biomineralization processes and cause the formation of smaller BMUs and disturbance lines (with different microstructure types). (4) Each microstructure possesses unique BMU size ranges. Comparison between different microstructure types can likely be accomplished by applying correction factors. BMUs of the same microstructure formed at the same time (i.e., under the same environmental conditions) have similar size ranges regardless of shell portion or shell growth rate. (5) Preparation of shells for microstructure morphometry can be easily accomplished by ultra-high polishing and etching. Semi-automated image processing methods can confidently extract quantitative morphological data of microstructural components from SEM images, thus providing a cost-efficient new analytical method. Our study laid the foundation for temperature reconstructions based on the shell microstructure. Additional species and microstructure types should be investigated to identify taxa with microstructures that vary less strongly through lifetime and are less affected by other environmental parameters than temperature. Future studies should conduct experiments on specimens reared under constant temperature while varying other environmental parameters such as salinity, food availability and dissolved oxygen content, in order to identify the effect of each parameter on the shell microstructure. Such studies could further unravel the interplay of environment, shell microstructure and chemistry, provide new insights into bivalve biomineralization processes, and refine microstructure-based temperature reconstructions.
Projektbezogene Publikationen (Auswahl)
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Morphological variations of crossed-lamellar ultrastructures of Glycymeris bimaculata (Bivalvia) serve as a marine temperature proxy. Estuarine, Coastal and Shelf Science, 237, 106658.
Höche, Nils; Peharda, Melita; Walliser, Eric O. & Schöne, Bernd R.
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Multi-isotopic and trace element evidence against different formation pathways for oyster microstructures. Geochimica et Cosmochimica Acta, 308, 326-352.
de Winter, Niels J.; Dämmer, Linda K.; Falkenroth, Michaela; Reichart, Gert-Jan; Moretti, Simone; Martínez-García, Alfredo; Höche, Nils; Schöne, Bernd R.; Rodiouchkina, Katerina; Goderis, Steven; Vanhaecke, Frank; van Leeuwen, Sonja M. & Ziegler, Martin
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Temperature-induced microstructural changes in shells of laboratory-grown Arctica islandica (Bivalvia). PLOS ONE, 16(2), e0247968.
Höche, Nils; Walliser, Eric O.; de Winter Niels, J.; Witbaard, Rob & Schöne, Bernd R.
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Microstructural Mapping of Arctica islandica Shells Reveals Environmental and Physiological Controls on Biomineral Size. Frontiers in Earth Science, 9.
Höche, Nils; Walliser, Eric O. & Schöne, Bernd R.
