Using NanoSIMS to map N distribution and uptake rates in cold-water coral skeletons
EMSL Project ID
60274
Abstract
Scleractinian (“stony”) corals produce skeletons of the mineral aragonite and form biodiverse reefs in both the tropical and cold deep ocean. Despite the broad interest and appreciation for corals as ecosystem engineers, ‘posterchildren’ for anthropogenic impacts, paleoenvironmental archives, and as medical biomaterials (i.e. bone implants), we still lack a fundamental mechanistic understanding of coral biomineralization. Coral skeletons contain organic matter rich in amino acids, polysaccharides and lipids bound within the aragonite mineral lattice. The amino acids in particular are nitrogen-rich and have been recent targets of study in the field of coral biomineralization due to their likely role in providing a framework for skeletal nucleation and determining the calcium carbonate polymorph corals use to build their skeletons. The isotopic composition of N bound within the coral aragonite lattice has also recently been shown to record marine N cycle changes. Thus, understanding the role of organic matter in coral skeletons, with an emphasis on nitrogen, is of interest both for improving mechanistic models of coral biomineralization and for ground-truthing a promising new paleoenvironmental indicator of marine biogeochemical cycles. This proposal aims to use NanoSIMS to investigate the spatiotemporal relationships between organic nitrogen bound in coral skeletons (CBON) and coral skeletal growth in a set of laboratory-cultured cold-water corals. These cultured corals were fed 15N enriched zooplankton at timed intervals. They were also grown in isotopically and elementally-enhanced seawater in a scheduled sequence to ‘label’ the timing of skeletal growth. Through these NanoSIMS analyses, we specifically seek to answer the following two questions: (1) what is the spatial distribution of N in CWC skeletons relative to key mineralogical and chemical features of the skeleton? And (2) how quickly does new N in the environment get incorporated into coral skeletons relative to rates of coral skeletal growth? The proposal requests ~two weeks of instrument time with assistance from Dr. John Cliff (one week using the Cs+ source and another using the O- source).
The ability to map spatial relationships between N-rich organic components and inorganic components (i.e. trace elements) at the micron scale will help elucidate inorganic-organic relationships in coral skeletons. Additionally, NanoSIMS mapping of timed isotope labels incorporated into our cultured corals will give us a relative sense of the rates at which CBON and inorganic components of the coral skeleton are constructed, furthering our understanding of the fundamental processes and pathways that govern coral biomineralization. Finally, the results of this study will help validate coral skeletons as a marine N cycle paleoenvironmental proxy through an improved understanding of N incorporation mechanism. This outcome would pave the way for using coral fossils to reconstruct past changes in biogeochemical cycles, improving our understanding of Earth System biogeochemistry and creating a baseline against which to contextualize modern marine biogeochemical change.
Project Details
Project type
Limited Scope
Start Date
2022-01-31
End Date
2022-04-22
Status
Closed
Released Data Link
Team
Principal Investigator