[Coral-List] Coral-List Digest, Vol 114, Issue 3

[Warner, Mark E.]

Scott,
Your statement recently posted to the coralist is simply not correct or supported by the existing data. You make the same erroneous statement in your 2013 Biogeosciences paper (which you cite on the list and link to) in which you provide two citations to back up this statement (Ralph et al. 2001 and Bhagooli and Hidaka 2004). Two citations do not make a trend or warrant such a blanket statement.

The reality is that the thermal response of many cnidarians is complicated by many things, including the rate of thermal heating and the susceptibility of the animal and the resident Symbiodinium. While it is true that there are some cases of thermal stress resulting in the rapid expulsion of Symbiodinium that are photochemically unaltered (I've measured this myself), there are many many other examples of photochemically damaged Symbiodinium released from heated corals as well as many studies with cultured Symbiodinium showing their thermal sensitivity with no host interaction and well within the range of temperatures known to cause natural bleaching.

Kind regards,
Mark Warner

Message: 3
Date: Mon, 5 Feb 2018 12:58:24 +1000
From: Scott Wooldridge <swooldri23 at gmail.com<mailto:swooldri23 at gmail.com>>
Subject: Re: [Coral-List] Warming makes Symbiodinium selfish
To: Coral -List <coral-list at coral.aoml.noaa.gov<mailto:coral-list at coral.aoml.noaa.gov>>


 Indeed,
it is already known that most expelled symbiodium remain photosynthetically
competent, and can handle temperatures well beyond thermal bleaching
thresholds. However, this presents a problem for the coral. An ideal candidate
symbiont would have a low growth rate during warming. But if such a
symbiont existed, it would also be a very poor candidate during ?normal?
conditions or back through the cooler seasons. I have previously discussed
these issues:


https://www.researchgate.net/publication/307695433_Breakdown_of_the_coral-algae_symbiosis_Towards_formalizing_a_linkage_between_warm-water_bleaching_thresholds_and_the_growth_rate_of_the_intracellular_zooxanthellae



______________________________
Mark E. Warner, Ph.D.
Professor
Associate Director,
Marine Biosciences

University of Delaware,
College of Earth, Ocean, and Environment
School of Marine Science and Policy
______________________________