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Does Temperature and UV Exposure History Modulate the Effects of Temperature and UV Stress on Symbiodinium Growth Rates?
ROGERS, J. E., D. T. MARCOVICH, AND S. N. GALLAHER. Does Temperature and UV Exposure History Modulate the Effects of Temperature and UV Stress on Symbiodinium Growth Rates? BULLETIN OF MARINE SCIENCE 86(3):743-761, (2010).
Here we examine the following question "Does acclimation in the presence and absence of UV to elevated temperature reduce temperature and UV sensitivity of Symbiodinium cultures?" We report the growth rates and upper lethal thermal limits of Symbiodinium growth for cultures exposed to a series of increasing temperatures in the presence or absence of UV following their acclimation to different temperatures, at high and low level of PAR and in the presence or absence of UV.
Temperature and ultraviolet radiation (UV) alone or in combination are known to inhibit the growth of Symbiodinium isolates. This conclusion was drawn from a number of studies having widely different exposure scenarios. Here we have examined the effects of pre-exposure acclimation conditions (PAR, UV, and temperature) on the growth of four Symbiodinium isolates exposed to elevated temperature and UV radiation, alone or in combination. The sensitivity of the four isolates to elevated temperature or UV exposure as measured by growth was unaffected by the level of PAR exposure (90 or 700 μmol m-2 sec-1) during the acclimation process. Acclimation to elevated temperature led to decreased sensitivity to sub-lethal temperature exposure for one of the four isolates and for another isolate acclimation to UV exposure led to decreased sensitivity to sub-lethal effects of UV. However, for three of the isolates acclimation did not markedly reduce the impacts of either temperature or UV at temperatures near their upper lethal limit. In the context of the coral reef environment, our results suggest that thermal or UV stress history may reduce coral bleaching at sub-lethal temperatures and UV levels but may or may not increase the upper thermal limit for coral lethality.