Fossil Corals With Various Degrees of Preservation Can Retain Information About Biomineralization-Related Organic Material

Abstract

Scleractinian corals typically form a robust calcium carbonate skeleton beneath their living tissue. This skeleton, through its trace element composition and isotope ratios, may record environmental conditions of water surrounding the coral animal. While bulk unrecrystallized aragonite coral skeletons can be used to reconstruct past ocean conditions, corals that have undergone significant diagenesis have altered geochemical signatures and are typically assumed to retain insufficient meaningful information for bulk or macrostructural analysis. However, partially recrystallized skeletons may retain organic molecular components of the skeletal organic matrix (SOM), which is secreted by the animal and directs aspects of the biomineralization process. Some SOM proteins can be retained in fossil corals and can potentially provide past oceanographic, ecological, and indirect genetic information. Here, we describe a dataset of scleractinian coral skeletons, aged from modern to Cretaceous plus a Carboniferous rugosan, characterized for their crystallography, trace element composition, and amino acid compositions. We show that some specimens that are partially recrystallized to calcite yield potentially useful biochemical information whereas complete recrystalization or silicification leads to significant alteration or loss of the SOM fraction. Our analysis is informative to biochemical-paleoceanographers as it suggests that previously discounted partially recrystallized coral skeletons may indeed still be useful at the microstructural level.

Glacial-aged development of the Tunisian Coral Mound Province controlled by glacio-eustatic oscillations and changes in surface productivity

“…In addition, our Mn/Ca ratios are within the range observed in benthic calcitic/aragonitic foraminifera and aragonitic corals after chemical cleaning (e.g. Glock et al, 2012;Fhlaithearta et al, 2010;Drake et al, 2021). Therefore, our low levels of Mn/Ca ratios allow to rule out the presence of significant secondary (i.e.…”

Zooplankton as the primary diet for cold-water scleractinian corals (CWCs): implications for the CWC marine N cycle proxy and trophic ecology

“…A robust coldwater coral archive of δ 15 N-PON can complement the existing suite of nitrogen proxies by reducing the potential biases almost inevitable for each individual proxy, allowing for a broader geographic and temporal reconstruction, and increasing resolution of the proxy record. Foremost, as with foraminifera and diatom shells, organic material trapped within the coral's original aragonite mineral lattice is presumably protected from diagenetic alteration (Drake et al 2021); coral skeletons can be inspected for contamination and recrystallization (e.g., borings) using microscopic techniques to avoid compromised areas (Gothmann et al 2015). CWCs have a broad geographic distribution, being present in all ocean basins from the surface to 5000 m (Freiwald, 2002).…”