SEMINAR: MBF602 Ross Cunning Friday 3-11-11, 1pm S/A 103

[Ross Cunning <rcunning@rsmas.miami.edu>]

Community dynamics of Symbiodinium in individual coral colonies during a natural warming and bleaching event

            The symbiotic algal community present within a single coral colony can include multiple Symbiodinium taxa that differ in aspects of their physiology such as growth rates, photosynthetic efficiency, amount of nutrient translocation, and stress tolerance. As environmental conditions fluctuate, the relative fitness and performance of different symbiont taxa may be altered, leading to changes in symbiont community composition. However, the drivers, magnitude, and patterns of Symbiodinium community dynamics are poorly understood. To begin filling these knowledge gaps, we tracked the densities of clade C and clade D Symbiodinium within individual colonies of Pocillopora damicornis held under natural conditions over a 6-month period of warming that culminated in a bleaching event. New multiplex real time PCR (rtPCR) assays were developed targeting the actin gene region of Symbiodinium clades C and D and P. damicornis in order to estimate symbiont to host cell ratios for both symbiont taxa. Results indicate that during a 4-month period of gradual warming with no observed bleaching, significant changes in symbiont to host cell ratios occurred, characterized primarily by increases in clade D relative to clade C. When visual bleaching began, corals hosting mostly clade C bleached severely and corals hosting mostly clade D did not, suggesting a quantitative relationship between symbiont community composition and bleaching severity. Variable patterns of Symbiodinium community changes throughout the warming and bleaching events among different coral colonies may be related to differences in initial symbiont community composition (i.e. incumbent taxa), relative proportions of clade C and clade D, host genotype, or stochastic effects. This study indicates that Symbiodinium communities can be highly dynamic during natural environmental fluctuations and under stress, and may play a role in coral acclimatization to environmental change.

Ross Cunning

Marine Biology and Fisheries

Entered PhD Program: Fall 2008

Advisor: Andrew Baker