[Coral-List] Fwd: CO2-limitation of algal endosymbionts in hospite is common

[Scott Wooldridge]

The increasing evidence-base indicating that intracellular CO2-limitation
underpins thermal coral bleaching has fundamental implications for the
premise that we may be able to lab-engineer a "super coral" by (eternally)
evolving heat-resistant strains of algae and transplanting them back into
coral hosts (so-called assisted evolution).

If CO2-limitation is the underpinning mechanism, then a heat-resistance
strain (per se) offers no real benefits, since it is the heat-dependent
growth (division) rate that is ultimately the parameter defining thermal
bleaching limits. I have previously written on this:

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

The conundrum is, that in establishing the symbiosis, a low algae growth
rate is disadvantageous - providing a selective advantage to faster growing
strains/clades. Also, slower growing (lower metabolism/respiration) strains
are unlikely to generate the same amount of photosynthate for the coral
host. The desired outcome for a slow dividing algal strain at higher
temperature is thus at odds with the requirement of the coral during
'normal' conditions. And perhaps explains why thermal bleaching thresholds
are so distinct, and why no super strains have ever evolved naturally.

All of which again leads to my thesis that strongly autotrophic symbiotic
corals are "the living dead" in the Anthropocene ocean:


https://www.researchgate.net/publication/317100418_
Instability_and_breakdown_of_the_coral-algae_symbiosis_
upon_exceedence_of_the_interglacial_pCO2_threshold_
260_ppmv_the_%27%27missing%27%27_Earth-System_feedback_mechanism

The best we can do, is to assist the coral host by ensuring that reef
environments remain strongly oligotrophic - thereby limiting the
'potential' temperature-dependent growth rates of the intracellular algae.

https://www.researchgate.net/publication/235762816_Safeguarding_coastal_coral_communities_on_the_central_Great_Barrier_Reef_Australia_against_climate_change_Realizable_local_and_global_actions


scott

https://www.researchgate.net/profile/Scott_Wooldridge


---------- Forwarded message ----------
From: Scott Wooldridge <swooldri23 at gmail.com>
Date: Thu, Aug 17, 2017 at 9:11 AM
Subject: CO2-limitation of algal endosymbionts in hospite is common
To: coral-list at coral.aoml.noaa.gov


Dear Fellow Coral Reef Researchers,

Just drawing attention to this excellent new manuscript by Radecker et al.
which highlights well that, "CO2 limitation of Symbiodinium is a common
feature of stable cnidarian holobionts".

http://journal.frontiersin.org/article/10.3389/fmars.2017.00267/full


Results such as these provide strong support for the role of light- adn
temperature driven CO2-limitation as the primary driver of mass coral
bleaching events:

https://www.researchgate.net/publication/240506685_A_new_
conceptual_model_for_the_warm-water_breakdown_of_the_coral-
algae_endosymbiosis

And explains why strongly autotrophic symbiotic corals are "the living
dead" in the Anthropocene ocean:


https://www.researchgate.net/publication/317100418_
Instability_and_breakdown_of_the_coral-algae_symbiosis_
upon_exceedence_of_the_interglacial_pCO2_threshold_
260_ppmv_the_%27%27missing%27%27_Earth-System_feedback_mechanism


The results also infer the crucial importance of getting the
experimental/laboratory light requirements correct for testing bleaching
mechanism, and making inference from the lab to ecosystem scale. I will
write further on this in a separate listing.

scott

https://www.researchgate.net/profile/Scott_Wooldridge