[Coral-List] Coral on the Great Barrier Reef was 'cooked' during 2016 marine heatwave. REALLY? REALLY? REALLY? #2

Risk, Michael riskmj at mcmaster.ca
Fri Apr 27 10:01:08 EDT 2018

Hello John.

Thank you for that post. We need to keep discussing the science, and we need to keep doing so in a supportive, collegial manner. This is an extremely important matter, not only for the future of reefs, but also-for us humans. So let’s keep it polite.

Data are always good to have. It’s not so long ago that someone posted on this list the bald assertion that coral decline in the Caribbean was due to recent heating. No data were provided, and the post ignored the fact that Caribbean decline began almost certainly in the 1950’s and was well under way by the 70’s; loss was most pronounced near centres of human habitation, and decline has been linked, in several/many papers, to LBSP.

I know you have a paper asserting that coral loss on remote areas is just as fast as near centres of habitation. Personally, I would soft-pedal this self-citation until more people agree with you. In the meantime, I suggest you try to find the beautiful reefs of Nyamuk Besar on any map of modern reefs…you won’t, it’s gone, see the seminal work of Tom Tomascik. 

The concept of “remote” reefs is a difficult one. Thirty years ago, Paul Sammarco and I were able to establish that corals on the GBR, at  the edge of the shelf 100km from a sparsely-populated coastline, still obtained a significant fraction of their food from terrestrial sources. If remote reefs are just as badly hit, then…Scripps has wasted all that money working on them??? (You should let them know.)

I think Scott has some excellent, if depressing, points. I would go a bit further. Present rates of sea-level rise are accelerating, and are already past the critical levels at which reef growth can keep pace. (And recall, those levels were suggested for the Holocene Transgression, when the transgressing ocean was a lot cleaner than the next one will be.) Present rates of coral loss are unsustainable. There is no sign humans are prepared to undertake cleaning up the oceans, and there is no sign we will limit CO2 production. Your country is a noted outlier here, and even in better-educated, kindly Canada, we are still debating whether we should build a pipeline to the west coast to carry tarsands bitumen to the East. Present efforts to “save” reefs by breeding super-corals, selecting for heat resistance, pumping water, moving corals, shading reefs…these are all a waste of time and effort.

We would be far better off maintaining coral tissue banks for some far off, better time, and putting the money and talent to better use. We will need  somehow to replace the protein that reefs currently provide for coastal communities, and we will need to feed and house the 100’s of millions about to be displaced. We have more important research priorities.


> On Apr 23, 2018, at 8:36 AM, Bruno, John <jbruno at unc.edu> wrote:
> Dear Scott,
> Thank you for sharing your idea about the real cause of mass bleaching on the GBR. As your’e probably aware http://www.co2science.org (a fossil fuel industry funded website) has been pushing this idea for a while. Arguing that pollution, fishing, seaweed etc are the real reason corals are bleaching and dying. Despite that, I’m open to the hypothesis. But based on past experiences on the coral-list, it seems to me the more vocal and confident people are about the role of nutrients, the less data / science they have in support of their explanations.
> In your case, what makes you think thermal stress was low or lower in 2016? You claimed DHW was only 3-4, but that contradicts the evidence: Hughes et al 2081 report that across the northern GBR, DHW was ~ 8-14 preceding the event and that severe bleaching occurred on reefs with DHW values of ~6-10. The NOAA Coral Reef Watch portal indicates the same:  https://coralreefwatch.noaa.gov/vs/gauges/gbr_far_northern.php
> Moreover, 2016 was the warmest year on earth in recorded history (NOAA ranks 2009 as the 8th warmest). The ABM confirms this for the GBR: 2016 was the warmest ever, and far warmer than 2009: https://www.dropbox.com/s/2q9uk1xewedtp58/Feb-2016-sea-surface-temperature.png?dl=0
> So your’e wrong about the thermal stress. And you don’t provide any values on nutrient concentration. While chlorophyll conc. is often generally indicative of nutrient conc., the relationship is very messy and chlorophyll can’t be used to make precise predictions about DIN. For one, other factors influence chlorophyll, including temperature, predation, other nutrients, etc. And to make such a comparison, you’d have to control for other factors demonstrated to have strong effects on community thermal sensitivity, eg coral composition and cover.
> Again I’m open to the idea and anything we can do to meaningfully reduce bleaching. But wouldn’t you think that if local N pollution increased bleaching sensitivity by ~2C (Wooldridge<https://www.researchgate.net/profile/Scott_Wooldridge> 2009) we’d be able to detect that in nature? Why would reefs in pristine locations ever bleach? We've seen so many highly isolated, “pristine” reefs bleach w mass coral mortality over the last decade (not only the N GBR), I’ve become suspicious of claims about local drivers of bleaching sensitivity. Moreover, we’re losing coral as rapidly on isolated atolls as we are on reefs adjacent to inhabited, industrialized coastlines (https://www.nature.com/articles/srep29778).
> Regardless, I appreciate you sharing your passion and ideas. But maybe next time come armed with some evidence.
> John Bruno
> Professor, Dept of Biology
> UNC Chapel Hill
> www.johnfbruno.com<http://www.johnfbruno.com>
> 🐠🐋🧜‍♂️🐟🦐 🦈🦑
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