4.7 Article

Coherent tracer correlations in deep-sea corals and implications for biomineralization mechanisms underlying vital effects

Journal

GEOCHIMICA ET COSMOCHIMICA ACTA
Volume 343, Issue -, Pages 304-322

Publisher

PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2022.12.006

Keywords

Deep-sea Corals; Oxygen and Carbon Isotopes; Minor; Trace Elements; Vital Effects; Internal pH Elevation; Growth Rate Dependence

Ask authors/readers for more resources

Deep-sea corals serve as an important record of past oceans and studying their vital effects is crucial for paleoceanographic applications. By analyzing stable isotopes, minor and trace metals, we observed spatially coherent tracer correlations in individual corals. Our findings provide insights into the biomineralization mechanisms and the response of marine calcification to environmental stress. Understanding these mechanisms is essential for accurate use of deep-sea coral tracers and predicting the impact of ocean acidification.
Deep-sea corals are a useful archive of thermocline, intermediate, and deep waters in past oceans. However, application of traditional oceanographic tracers to deep-sea corals remains a challenge due to our insufficient understanding of their vital effects. Deep-sea corals are ideal test organisms to study the mechanism underlying vital effects generally, due to the large tracer gradients in individual corals living under relatively constant environmental conditions. Lessons learned from these corals might apply to other scleractinia and to marine calcifiers more generally. Here we present stable isotope, minor and trace metal (Me/Ca ratios) data in a suite of modern Desmophyllum dianthus specimens, collected over multiple spatial scales in individual corals (bulk, micromill, SIMS, NanoSIMS), with multi-proxy analyses made on the same material whenever possible. Spatially coherent Me/Ca correlations are observed in the fibrous aragonite of individual corals, including positive correlations between Mg/Ca, Li/Ca and B/Ca, as well as negative correlations between Mg/Ca and Sr/Ca, consistent with previous studies. We also for the first time document strong correlations between the isotopic (818O and 813C) and elemental compo-sitions of the skeletons, most notably a negative correlation between 818O and Mg/Ca. The centers of cal-cification (COCs) in the coral skeletons show distinct tracer correlations from the aragonite fibers that possibly reflect a more complicated formation mechanism. We interpret the spatially coherent tracer cor-relations in deep-sea corals with a numerical model of coral calcification previously developed for stable isotopes that considers the role of the enzyme carbonic anhydrase in the calcification processs. With the carbonate chemistry in the model constrained by the stable isotope data, we are able to explain the observed Me/Ca correlations as well as their range of variability, as a result of internal pH elevation in the extracellular calcifying fluid (ECF) of the corals with limited Ca-pumping through the calicoblastic membrane. In particular, the positive Mg/Ca-B/Ca correlation in the fibrous aragonite suggests a borate (B(OH)4-) substitution for carbonate ion (CO32-) incorporation mechanism in biogenic aragonite. We also suggest the growth rate dependence of the incorporation of minor and trace elements based conceptually on an ion-by-ion growth model may help explain the absolute Me/Ca values in biogenic aragonites. Finally, we generally find more limited tracer variability in corals from undersaturated seawater com-pared to their counterparts from supersaturated conditions, suggesting a limit to their internal pH eleva-tion in response to this environmental stress. Understanding the biomineralization mechanisms underlying the vital effects is important for better use of these tracers for paleoceanographic applications, and may shed light on the response of marine calcification to future ocean acidification.(c) 2022 Elsevier Ltd. All rights reserved.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.7
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available