Morphological variations of crossed-lamellar ultrastructures of Glycymeris bimaculata (Bivalvia) serve as a marine temperature proxy
| Autor: | Nils Höche, Eric Otto Walliser, Melita Peharda, Bernd R. Schöne |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
0106 biological sciences
Glycymeris 010504 meteorology & atmospheric sciences biology Brackish water δ18O 010604 marine biology & hydrobiology Glycymeris bimaculata Aquatic Science Oceanography biology.organism_classification Bivalvia 01 natural sciences Isotopes of oxygen 13. Climate action Sclerochronology Paleoclimatology 14. Life underwater Geology 0105 earth and related environmental sciences temperature proxy bivalve sclerochronology paleoclimatology ultrastructure nearshore environment Adriatic Sea |
| Popis: | Bivalve shells are among the most promising archives for high-resolution seawater temperature reconstructions. However, despite major research advances in bivalve sclerochronology over the past decades, estimating water temperature from shells remains a challenging task. This is largely because the most frequently used and widely accepted temperature proxy in bivalves, i.e., the shell oxygen isotope (δ18Oshell) value, also requires knowledge of changes in δ18O of the water (δ18Owater) in which the bivalve lived, which is rarely available for ancient environments. According to a few recent studies, the size and shape of individual biomineral units (BMUs) of the shell ultrastructure may serve as an independent temperature proxy that is also less vulnerable to diagenetic changes than isotope chemical proxies. However, the crossed-lamellar ultrastructure, which occurs in ca. 90% of all mollusk species, has hitherto not been investigated. Here, we evaluate the potential use of morphological properties of the BMUs in Glycymeris bimaculata as a proxy for water temperature. For this purpose we introduce a suitable preparation technique (immersion for 2 m in 0.001 vol% formic acid followed by 20–30 m in 3.5 vol% H2O2) and an automated image processing technique that tremendously speed up ultrastructure analysis (5 s versus one to 2 h image processing time with automated and manual methods, respectively) and increase the robustness of BMU measurements. Glycymeris is a particularly useful target taxon, because it is a cosmopolitan genus with evolutionary roots in the Upper Cretaceous, and some species of Glycymeris can attain a lifespan of more than two hundred years, which allows for long-term, high-resolution paleoclimate reconstructions. As in other previously studied ultrastructures, larger and more elongated BMUs formed in warmer water permitting temperature estimates with an error of 2.3 °C (1 σ). Since the new temperature proxy is unaffected by other environmental variables, including salinity, it can potentially be applied to (modern and fossil) specimens from brackish environments. |
| Databáze: | OpenAIRE |
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