Articles | Volume 12, issue 19
Biogeosciences, 12, 5677–5687, 2015
Biogeosciences, 12, 5677–5687, 2015

Research article 08 Oct 2015

Research article | 08 Oct 2015

A novel paleo-bleaching proxy using boron isotopes and high-resolution laser ablation to reconstruct coral bleaching events

G. Dishon1, J. Fisch2, I. Horn3, K. Kaczmarek4, J. Bijma4, D. F. Gruber5, O. Nir1, Y. Popovich1, and D. Tchernov1 G. Dishon et al.
  • 1The Leon H. Charney School of Marine Sciences, University of Haifa, Mount Carmel, Haifa 31905, Israel
  • 2Rosenstiel School for Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA
  • 3Leibniz-University of Hanover, Institute for Mineralogy, Callinstr. 3, 30167 Hanover, Germany
  • 4Alfred Wegner Institute Helmholtz center for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
  • 5Department of Natural Sciences, City University of New York, Baruch College, P.O. Box A-0506, 17 Lexington Avenue, New York, New York 10010, USA

Abstract. Coral reefs occupy only ~ 0.1 percent of the ocean's habitat, but are the most biologically diverse marine ecosystem. In recent decades, coral reefs have experienced a significant global decline due to a variety of causes, one of the major causes being widespread coral bleaching events. During bleaching, the coral expels its symbiotic algae, thereby losing its main source of nutrition generally obtained through photosynthesis. While recent coral bleaching events have been extensively investigated, there is no scientific data on historical coral bleaching prior to 1979. In this study, we employ high-resolution femtosecond Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) to demonstrate a distinct biologically induced decline of boron (B) isotopic composition (δ11B) as a result of coral bleaching. These findings and methodology offer a new use for a previously developed isotopic proxy to reconstruct paleo-coral bleaching events. Based on a literature review of published δ11B data and our recorded vital effect of coral bleaching on the δ11B signal, we also describe at least two possible coral bleaching events since the Last Glacial Maximum. The implementation of this bleaching proxy holds the potential of identifying occurrences of coral bleaching throughout the geological record. A deeper temporal view of coral bleaching will enable scientists to determine if it occurred in the past during times of environmental change and what outcome it may have had on coral population structure. Understanding the frequency of bleaching events is also critical for determining the relationship between natural and anthropogenic causes of these events.

Short summary
This paper offers a new methodology to study paleo-coral bleaching events using high-resolution femtosecond Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry. Coral bleaching records only go back several decades, but this new proxy allows the study of bleaching events that occurred tens of thousands of years ago. Unlike other methods, the high-resolution of the method can detect bleaching events that occur over very short time periods, just a few weeks.
Final-revised paper