[Coral-List] Warming makes Symbiodinium selfish

Scott Wooldridge swooldri23 at gmail.com
Sun Feb 4 21:58:24 EST 2018

Just drawing young coral scientists and coral reef managers attention to
this excellent paper by David Baker and colleagues.


It is essential reading for developing your thoughts around how to design
strategies/approaches to help the coral symbiosis mitigate future ocean
warming and acidification. The paper experimentally demonstrates that far
from being the weak-link in the coral bleaching sequence, the algal
symbiodinium thrive and proliferate under warming conditions (esp. if
nutrient replete). However, far from being beneficial for the symbiosis,
the enlarged symbiont population becomes a metabolic burden to the coral
host – thereby reducing the capacity of the host to maintain essential
(energy-dependent) symbiotic relations during period of anomalous summer
heat/light stress. See:


Thus, the desire by many research groups to selective breed “heat tolerant”
symbiodinium is fundamentally flawed. This is because the attribute of
is not heat tolerance (per se) but the thermal-specific growth rate. 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:



The manuscript by David Baker and colleagues also challenges the notion
that assisted evolution strategies could potentially be used to breed
a superior
(thermally tolerant) coral host. This is because the coral host is not
thermally stressed per se. The only adaptive trait of benefit for the coral
host is to gain enhanced plasticity in its ability to obtain energy for
heterotrophic carbon sources. See:



The manuscript by David Baker and colleagues does however provide excellent
experimental proof (and mechanistic insight) for previous claims that a
significant benefit of nutrient pollution mitigation schemes will be
manifest as higher coral bleaching thresholds: See.



Moreover, the manuscript by David Baker and colleagues confirms that this
information can already to used to guide the process of spatially
ranking bleaching-resistant
reef areas for enhanced protection. For example, see Fig. 6 in the below
manuscript which identifies the most bleaching resistant sites on the Great
Barrier Reef. See:


I trust that these observations will assist your thoughts in these areas,
whether you primary interest lies in coral physiology or coral reef
management. My hope is that someone can use these observations to come up
with a novel "salvation" strategy.

My personal feeling is that geological history suggests this will not
occur. By this i mean that not all corals will go extinct, but that coral
reefs will go extinct - at least until suitable environmental conditions
return - principally pCO2 <260ppm. See:




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