SEMINAR: MBF602 9/23/11 S/A 103, 1:00pm Jay Fisch: Boron Isotopic Analysis as a paleo-tracer for coral bleaching

["Maxine Williams" <mwilliams@rsmas.miami.edu>]

MBF602 9/23/11 S/A 103, 1:00pm Student Speaker Jay Fisch

 

Boron Isotopic Analysis as a paleo-tracer for coral bleaching

 

The increasing occurrence of coral bleaching events is mainly attributed to the rise in sea surface temperature resulting from increased anthropogenic CO₂ emissions.  The question arises if bleaching has occurred in the past during previous interglacial maximums or if it is now evident as a consequence of human perturbation.  Boron isotopes may serve as a proxy for coral bleaching and the key to answering this question.

Boron isotopic fractionation(d¹¹B) in scleractinian skeletons is shown to decrease with decreasing seawater pH.  The majority of these studies discount the biological effect the coral holobiont may play in altering seawater chemistry.  During bleaching events, the loss of the coral’s symbiotic algae leads to a severe reduction in photosynthesis and a subsequent buildup of CO₂.  This results in a reduction in pH in the coral’s diffusive boundary layer which was measured to drop ~0.3 pH units during the bleached period.  The hypothesis was that this drop in pH should be evident in the d¹¹B values incorporated in the skeleton during calcification. With a new technique utilizing femtosecond laser ablation, d¹¹B values were measured in coral skeletons deposited during an experimental bleaching event. A depletion of up to 4.5‰ was observed.  These results support the potential use of d¹¹B as a paleo-tracer for coral bleaching.

 

Jay Fisch

Entered PhD Program: Fall 2011

B.A. in Biological Sciences (Rutgers University, 2007)

M.Sc. in Evolution, Systematics and Ecology (The Hebrew University of Jerusalem, 2009)

Advisor: Dr. Chris Langdon