Confocal Raman microscopy in sclerochronology: A powerful tool to visualize environmental information in recent and fossil biogenic archives

Abstract

Biological hard parts and skeletons of aquatic organisms often archive information of past environmental conditions. Deciphering such information forms an essential contribution to our understanding of past climate conditions and thus our ability to mitigate the climatic, ecological, and social impacts of a rapidly changing environment. Several established techniques enable the visualization and reliable use of the information stored in anatomical features of such biogenic archives, i.e., its growth patterns. Here, we test whether confocal Raman microscopy (CRM) is a suitable method to reliably identify growth patterns in the commonly used archive Arctica islandica and the extinct species Pygocardia rustica (both Bivalvia). A modern A. islandica specimen from Norway has been investigated to verify the general feasibility of CRM, resulting in highly correlated standardized growth indices (r > 0.96; p < 0.0001) between CRM-derived measurements and measurements derived from the established methods of fluorescence microscopy and Mutvei's solution staining. This demonstrates the general suitability of CRM as a method for growth pattern evaluation and cross-dating applications. Moreover, CRM may be of particular interest for paleoenvironmental reconstructions, as it yielded superior results in the analysis of fossil shell specimens (A. islandica and P. rustica) compared to both Mutvei staining and fluorescence microscopy. CRM is a reliable and valuable tool to visualize internal growth patterns in both modern and fossil calcium carbonate shells that notably also facilitates the assessment of possible diagenetic alteration prior to geochemical analysis without geochemically compromising the sample. We strongly recommend the CRM approach for the visualization of growth patterns in fossil biogenic archives, where conventional methods fail to produce useful results.

The Prismatic Layer of Pinna: A Showcase of Methodological Problems and Preconceived Hypotheses

“…These results are in accordance with the SEM observations of the inner structure of the tablets [31], showing that the central region of the tablets of gastropods and cephalopods are mainly organic. In situ maps (infrared and Raman spectrometries) also provide information on the nature of the mineral and organic components, as well as their respective location [32,33]. As for infrared and Raman spectrometry, and TOF-SIMS, both spectra and maps are available in XANES studies.…”

The Origin and Role of Organic Matrix in Coral Calcification: Insights From Comparing Coral Skeleton and Abiogenic Aragonite

“…Two main approaches to characterize organics from Raman spectra have been used in the literature: quantifying the background fluorescence in the 2,400-2,700 cm −1 region (Nehrke et al, 2011;Wall and Nehrke, 2012;Beierlein et al, 2015) and anomalies in the 2,850-3,000 cm −1 region attributed to C-H bonds (Lin-Vien et al, 1991;Perrin and Smith, 2007;Jolivet et al, 2008;Nehrke et al, 2011;Von Euw et al, 2017). Here, we evaluated the organic matter content in a variety of ways based on the data in these two regions of the spectra.…”

The effects of environment on &lt;i&gt;Arctica islandica&lt;/i&gt; shell formation and architecture

“…Electron backscatter diffraction (EBSD) has been previously used to determine the crystallographic orientation of gastropod (Fryda et al, 2009;Pérez-Huerta et al, 2011) and bivalve microstructural units (Checa et al, 2006;Frenzel et al, 2012;Karney et al, 2012). Whereas, CRM on mollusk shells is generally applied within studies on taphonomic mineralogical alteration and pigment identification (Stemmer and Nehrke, 2014;Beierlein et al, 2015). Both techniques provide considerably high spatially resolved analysis up to 250 nm, allowing for the identification of individual structural units at micrometer and nanometer scale (Cusack et al, 2008;Karney et al, 2012).…”