Trace metal composition and growth habit of cultured cold-water coral aragonite: proxy calibration experiments

5th Past Global Changes (PAGES) Ocean Sciences Meeting, 9-13 May 2017, ZaragozaWith life-spans of decades to more than 1000 years and skeletons suitable for precise U/Th dating, cold-water corals have the potential to provide climate and environmental information with a temporal resolution that can rarely be achieved in sediment cores. We have embarked on long-term culturing experiments using Desmophyllum dianthus (a solitary deep coral, typical lifespan 100 yr) in order to calibrate geochemical proxies for dissolved nutrients and the carbonate system (poster by Pelejero et al., this meeting), controlling seawater composition and pH in a flow-through aquarium. An early goal is to better understand and quantify skeletal extension patterns and growth rates on time scales of months-years, currently poorly known for this species. To locate regions of new skeletal growth for subsequent chemical analysis, we tested the suitability of Alizarin and Calcein dyes as a fluorescent markers of the growing surface of D. dianthus septa, both upon initiation and at critical time points during culturing experiments. This approach results in stained skeletal sections that are quickly and easily analyzed in 3D by confocal microscopy. Results showed that growth over several months was localized, and extension rates among and even within individual septa varied greatly. Calcein staining lines were particularly useful in selecting regions for analysis by laser ablation ICP-MS. Spiking aquarium seawater with periodically varied enriched Pb isotopes proved to be a relatively inexpensive way to verify growth intervals and confirm complex growth patterns interpreted from stain distribution. We will discuss initial results of analysis of new aragonite grown under tightly controlled seawater conditions with the aim of refining calibrations of the proxies P/Ca, Ba/Ca, U/Ca, and Li/Mg as proxies of dissolved nutrients, the carbonate system, and calcification temperaturePeer Reviewe