[Coral-List] So you think you understand coral bleaching?

[sealab at earthlink.net]

Hi Scott,

I think most all agree that “beyond the global imperative to mitigate future atmospheric CO2 emissions there still remains the need for effective local management actions that enhance the resistance and resilience of coral reef communities to the impacts of climate change”. Few would challenge that assumption or the idea that “we need to keep pressing for a more comprehensive understanding of the coral bleaching mechanism”, but in “extending your comments to their thought-provoking extreme”, could you have gone a bit too far?

If coral reef scientists devote virtually all their best thinking (99.9% is what you suggested) to finding “a cure” for coral bleaching, I fear that would have a devastating impact on efforts already underway to address the root causes of the problem. It seems to me that this way of thinking is consistent with the practice of traditional Western medicine which focuses on treating symptoms rather than taking a system-wide approach. Please excuse me if my interpretation seems naive - I’m not a scientist, but I’ve read a number of your papers and your latest hypothesis is most interesting in that it presents a novel way of looking at coral-algae symbiosis.

My question to you would be that although your thesis, if widely accepted , would alter some central restoration strategies, isn’t the ultimate success of any such efforts still dependent on local water quality improvements in combination with global CO2 reductions? And if so, wouldn’t the majority of the best thinking of coral reef scientists be put to better use if applied to those two goals rather than the development of bleach-resistant corals? If we can restore the natural ecological balance, wouldn’t the corals be able take care of the rest without the need for potentially contentious genetic modifications?

Finally, I don’t know why there is cause to characterize another scientist’s efforts as “light-weight, unjustified and damaging” especially considering that I can think of very few, if any in this field who have been more willing to put their reputations on the line by speaking truth to power. I had heard that the coral science community can be ruthless, even viscous at times. I was told that “they’ll eat their own”, but I’ve never really seen it played out. Seems to me that COVID-19 provides more than ample foreshadowing for the value of unity and cooperation in times of crisis. Your enthusiasm for seeking a better understanding of the dynamics involved in coral bleaching and for saving coral reefs from extinction is commendable, but perhaps your appeal would be more effectual if it did not so harshly discredit the work of others who are tirelessly in pursuit of similar goals.

Sincere regards,

Steve

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On 3/28/20, 7:09 AM, Scott Wooldridge <swooldri23 at gmail.com> wrote:

Hi Steve,

As you may have picked up, I was extending my comments to their thought-provoking extremes. Obviously, many scientists are doing innovative work on trying to better understand the inner working of the coral bleaching process. Indeed, I read a great summary report in a recent issue of PNAS, which is well worth a read.

https://www.pnas.org/content/117/5/2232.short

You are also correct that many scientists, managers and policy makers have been striving to improve reef water quality as an important conservation measure.

What I will say, however, is that what I am advocating is not the idea that poor water quality is just one (of many) additive stresses that impact on coral reefs, i.e. a contributing straw that helps breaks the camel’s back. Instead, I envisage inorganic nutrient enrichment as an intrinsic, co-determining driver of thermal coral bleaching. That is, excess nutrient enrichment increases the likelihood of coral bleaching (per unit thermal anomaly). To understand this better, and how it interacts with our efforts to reduce future rates of global warming, check out:

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

Abstract

The threats of wide-scale coral bleaching and reef demise associated with anthropogenic (global) climate change are widely known. Less well considered is the contributing role of conditions local to the reef, in particular reef water quality, in co-determining the physiological tolerance of corals to increasing sea temperatures and declining pH. Here, the modelled benefit of reduced exposure to dissolved inorganic nitrogen (DIN) in terrestrial runoff, which raises the thermal tolerance of coastal coral communities on the central Great Barrier Reef (Australia), is considered alongside alternative future warming scenarios. The simulations highlight that an 80% reduction in DIN ‘buys’ an additional ~50–60 years of reef-building capacity for No Mitigation (‘business-as-usual’) bleaching projections. Moreover, the integrated management benefits provided by: (i) local reductions of ~50% in DIN contained in river loads, and (ii) global stabilisation of atmospheric CO2 below 450 ppm can help ensure the persistence of hard-coral-dominated reefscapes beyond 2100. The simulations reinforce the message that beyond the global imperative to mitigate future atmospheric CO2 emissions there still remains the need for effective local management actions that enhance the resistance and resilience of coral reef communities to the impacts of climate change.

I hope this clears up some misconceptions, and assures people that beyond water quality improvements I DO also advocate strongly of the importance of reducing our carbon footprints.

But the central tenet of my previous post remains. We need to keep pressing for a more comprehensive understanding of the coral bleaching mechanism. It is not perfectly understood. Lots still remains to be discovered. And we should be excited by the challenges that presents, and the hope that remains for finding solutions to help save coral reefs from extinction.

For your consideration,

Scott