Investigating marine bio-calcification mechanisms in a changing ocean with in vivo and high-resolution ex vivo Raman spectroscopy.

Thomas M Decarlo,Paul Guagliardo,Steeve Comeau,Aleksey Sadekov,Malcolm T Mcculloch,Julie Trotter,Christopher E Cornwall,Laura Gajdzik,Emma C Thillainath

doi:10.1111/gcb.14579

Thomas M Decarlo, Paul Guagliardo + Show 7 more

Open Access

https://doi.org/10.1111/gcb.14579

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Abstract

Ocean acidification poses a serious threat to marine calcifying organisms, yet experimental and field studies have found highly diverse responses among species and environments. Our understanding of the underlying drivers of differential responses to ocean acidification is currently limited by difficulties in directly observing and quantifying the mechanisms of bio‐calcification. Here, we present Raman spectroscopy techniques for characterizing the skeletal mineralogy and calcifying fluid chemistry of marine calcifying organisms such as corals, coralline algae, foraminifera, and fish (carbonate otoliths). First, our in vivo Raman technique is the ideal tool for investigating non‐classical mineralization pathways. This includes calcification by amorphous particle attachment, which has recently been controversially suggested as a mechanism by which corals resist the negative effects of ocean acidification. Second, high‐resolution ex vivo Raman mapping reveals complex banding structures in the mineralogy of marine calcifiers, and provides a tool to quantify calcification responses to environmental variability on various timescales from days to years. We describe the new insights into marine bio‐calcification that our techniques have already uncovered, and we consider the wide range of questions regarding calcifier responses to global change that can now be proposed and addressed with these new Raman spectroscopy tools.

Highlights

The production of calcium carbonate (CaCO3) by marine calcifying organisms plays a key role in the global carbon cycle and influences the chemistry of the ocean (Berelson et al, 2007)
Recent studies have speculated that corals build their aragonitic skeletons from amorphous calcium carbonate (ACC) particles (Von Euw et al, 2017; Mass et al, 2017), that planktonic foraminifera form vaterite as a pre‐ cursor to calcite (Jacob, Wirth, Agbaje, Branson, & Eggins, 2017), and that some coralline algae stabilize their skeletons with dolomite and magnesite (Nash et al, 2011, 2013)
We present Raman spectroscopy techniques for investigating marine bio‐calcification mechanisms

Summary

| INTRODUCTION

The production of calcium carbonate (CaCO3) by marine calcifying organisms plays a key role in the global carbon cycle and influences the chemistry of the ocean (Berelson et al, 2007). Recent studies have speculated that corals build their aragonitic skeletons from amorphous calcium carbonate (ACC) particles (Von Euw et al, 2017; Mass et al, 2017), that planktonic foraminifera form vaterite as a pre‐ cursor to calcite (Jacob, Wirth, Agbaje, Branson, & Eggins, 2017), and that some coralline algae stabilize their skeletons with dolomite and magnesite (Nash et al, 2011, 2013). These unexpected findings imply greater complexities in marine bio‐calcification and underscore the need for further investigations into the mechanisms by which calcifi‐ cation occurs. We create high‐resolution (micron‐scale) ex vivo Raman maps of the calcium carbonate structures of a tropical coral, a deep‐ sea coral, a fish otolith, a foraminifer, and a coralline alga

| MATERIALS AND METHODS

| DISCUSSION

CONFLICT OF INTEREST