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An improved understanding of coral skeletons as environmental proxies and biomaterials by mapping organics and water at the nanoscale

EMSL Project ID


Scleractinian coral skeletons are highly sensitive to environmental change, can record environmental transformations through their geochemistry, and are of economic importance due to the habitat and protection their reefs provide to coastlines. While coral skeletons are mostly composed of the mineral aragonite, it has been known for decades that up to 3% by weight of the coral skeleton is composed of non-mineral phases: specifically, water and organic matter. Water and organic matter in coral skeletons have been investigated for their environmental proxy potential (i.e. ability to record biogeochemical processes) and linked to important material properties of coral skeletons. However, almost all of the information that currently exists on these phases in corals comes from bulk analyses. We still lack a nanoscale understanding of the distribution and incorporation of organic matter and water in coral skeletons. Developing such knowledge is critical because coral skeletons are structurally and geochemically heterogeneous, meaning that bulk studies fail to capture critical interactions between organics, water and aragonite. The existing gaps in knowledge make it difficult to capitalize on the environmental proxy potential of organics and water in coral skeletons and to fully understand the how these phases control the material and chemical properties of coral aragonite.

This proposal seeks to address the above mentioned knowledge gaps by developing a baseline, nanoscale understanding of elemental and molecular-level chemistry of organic matter and water in an existing sample set of natural and cultured coral skeletons. In close collaboration with staff at EMSL, the proposed work will involve using two cutting edge chemical imaging techniques, nanoSIMS and nanoFTIR, to map the elemental and molecular composition of organics and water in coral skeleton samples. Elements targeted with nanoSIMS include organic-associated elements such as S, N and also trace metals like Mg and K that are known to be sensitive to environmental variability. Molecules targeted with nanoFTIR include H2O and OH-, amide bonds, sulfates, and polysaccharides so as to fingerprint the presence of phases like proteins and sulfated polysaccharides that are known to exist in the coral skeleton from bulk studies.

The fundamental results obtained from the proposed work would provide a stepping stone for understanding how nanoscale patterns in organics and water in coral skeletons vary in direct response to changing environmental conditions. The will also inform how such changes affect coral skeletal material properties such as hardness and strength. These outcomes are in line with the EMSL and DOE-BER program missions of establishing a predictive understanding of complex biological and environmental systems that can inform models and improve our understanding of national infrastructure - in this case coastal infrastructure, habitat, and ecosystems supported by coral reefs.

Project Details

Project type
Exploratory Research
Start Date
End Date


Principal Investigator

Anne Gothmann
Saint Olaf College