[Coral-List] Evidence that ocean warming has caused most Caribbean coral loss

Risk, Michael riskmj at mcmaster.ca
Tue Apr 25 20:51:04 EDT 2017

   Hello John, colleagues.
   I hesitate to respond, because all too often these exchanges degenerate into
   two guys talking past each other. Nonetheless, I wish to make myself clear,
   and to clear up some items.
   When I referred to reefs declining before significant warming, I was taking
   temperature data from your post. I am well aware of the progress of warming
   of the Caribbean. You seem to infer that I have failed to post references to
   land-based stress going back to the 70's-but if you are publishing on the
   Caribbean, you know this literature as well as I do-or you should. To take
   but one example: Phil Dustan's work clearly shows decline well under way by
   the early 1970's-I encourage all to look at the depressing time-lapse photos
   he posts at [1]https://biospherefoundation.org/project/coral-reef-change/
   He attributes the decline to land-based pollution. In followup work in
   Florida, Craig Downs found that bleaching was accelerated by oxidative
   stress, probably from pesticides:
   In short, decline was well under way by the early 70's-but you knew this.
   One of the advantages of retrospective analyses of corals and gorgonians is
   that it allows us to generate baseline-ish data where none had existed
   before. In the case of the Florida Keys, Ward-Paige et al (2005: MEPS 296:
   155-163) relate that decline to changes in water quality. In their Fig. 5,
   the difference between 15N ratios from "clean" and "dirty" sites converge
   back in the early 70's. By the present, they differ by 2per mille (a value I
   have suggested elsewhere should trigger enforcement involvement). In short,
   the WQ started going bad in the 70's. Similarly, we were able to trace the
   decline in WQ in the Red sea off Jeddah since 1950, during which the reefs
   declined (Risk et al., 2009: MEPS 397: 219-226).
   Saying  we  have  not lost any reefs yet, just corals, is playing with
   semantics.  More  than  a decade ago, I was asked to evaluate the reef
   monitoring  programs  in  the Florida Keys. I had been away, mostly in
   Asia...and was horrified by what I learned. Coral had declined from 45%
   cover to <4% (and it's lower, now). In my report, I referred to this as a
   "regional mass extinction." This wording, although correct, was removed in
   the final copy. A substrate with a scattering of corals is not a reef. In
   fact (zowie, huge other subject!) there have been several recent papers
   pointing out that most modern reefs are in a negative balance, due to the
   nutrient-driven acceleration of bioerosion.
   You  miss  my point, about running experiments about survival rates of
   unstressed reefs. The examples you cite are not convincing. We have known
   for decades that terrestrial influence can extend >100km offshore (Sammarco
   et al., 1999: MEPS 180: 131-138, and earlier papers). I suggest another
   thought experiment: had terrestrial stresses been removed from the Florida
   Keys when Dustan first sounded the alarm, those reefs would now be healthier
   than those of Cuba, much closer to the warming centre. I can't say much
   about this Cuban MS I have, because it's under review, but they make it
   clear that yes, those reefs are generally in better nick than the Caribbean
   in general-except near sources of land-based pollution.
   There  are  a  lot  of very clever people in this field. Speaking very
   personally, I would like to see some of the smart biologists who spend their
   time mining others' papers for trends move out of their comfort zones and
   get into the chemical and geological aspects of this field. There's not a
   lot of time left.

   From: Bruno, John [jbruno at unc.edu]
   Sent: April 25, 2017 8:50 AM
   To: Risk, Michael
   Cc: coral-list at coral.aoml.noaa.gov
   Subject:  Re: [Coral-List] Evidence that ocean warming has caused most
   Caribbean coral loss
   Dear Mike, thank you for your ongoing interest in this topic and my post.
   "the  Caribbean had already lost more than half its reefs before water
   temperatures had increased by more than a fraction of a degree”
   This is a common misconception from folks unaware that global warming began
   many decades ago. Please have a look at the NOAA data plotted in this figure
   from my
   post: [3]http://theseamonster.net/2017/04/caribbean-bleaching/nclimate2915-f
   4/  Or the graphics in Kuffner et al 2014 below it. These data should sort
   you out. The Caribbean had clearly warmed significantly by the time mean
   coral  cover  had been roughly halved (around the mid-1980s). Also, we
   haven’t  lost  any reefs yet, what we’ve lost is coral cover (and fish
   Iv’e dove near Havana and I agree - its a mess and was probably locally
   impacted. And I don’t understand the logic in arguing managers should give
   up because climate change has had significant impacts on corals. I’ve said
   it a million times: local impacts need to be mitigated. We all agree on
   that.  I  think you’re underestimating managers and local conservation
   capacity. (All the managers I know acknowledge climate change but aren’t
   giving up). As the Ocean Optimism symposium highlighted over the weekend,
   local successes are realistic and very much meaningful and worthwhile.
   "and there is overwhelming evidence of land-based stress going back to the
   You have been promising this list-serv these references for years now. If
   you ever find them, please do share with us if you have the time.
   "how well could coral reefs survive ocean warming if they were not already
   stressed by [local] human impacts?”
   That experiment has been run dozens of times. On the northern GBR, on Scott
   Reef, off Southern Cuba or in the Bahamas, across the central Pacific, etc.
   The answer is not well at all..
   The reason is that local impacts do not appear to act synergistically with
   ocean warming. As Cote and Darling suggested
   0438), the interaction appears to be antagonistic, not synergistic. Either
   that or the impact of warming is so much stronger that it swamps the local
   and     synergistic     signals.    Also    see    Darling    et    al
   2010: [5]http://research.fit.edu/sealevelriselibrary/documents/doc_mgr/389/K


   1. https://biospherefoundation.org/project/coral-reef-change/
   2. http://www.haereticus-lab.org/coral-reefs-in-florida-keys-in-devastating-decline/
   3. http://theseamonster.net/2017/04/caribbean-bleaching/nclimate2915-f4/
   4. http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1000438
   5. http://research.fit.edu/sealevelriselibrary/documents/doc_mgr/389/Kenya_Coral_Reef_Stressors_Not_Synergistic_-_Darling_et_al.pdf

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