Perhaps you need to do a bit more reading ...

Debbie MacKenzie debimack at
Thu May 10 11:03:22 EDT 2001

Hi Ove,

Thanks for responding to my post. Glad you were amused! 

At 08:05 AM 5/10/01 +1000, you wrote:
>Dear Debbie,
>Much though I was amused by your article and proposal (that the "seas are
>starving" and this is why reefs are experiencing mass bleaching), I feel that
>you need to do a little more reading in the area of mass coral bleaching to
>correct the many errors.  My feeling is that you need to do more reading - a
>fact indicated by your reference list - I feel this probably underpins why
>came to such odd conclusions. 

The length of my reference list? Since when has that been the measure of
whether or not an idea is interesting and well thought out? I've read
umpteen things on the declining "condition"(fat content), and growth rates
of marine life overall, everything from marine mammals to all-groundfish,
large pelagics, small pelagics, etc. - and I obviously didn't list them all
there - but that's the pattern. (And it looks like the corals may be
developing the same problem.) Declining abundance and condition factor
simultaneously - contrary to "expectations" based on previous "knowledge"
(in fish, the one used to predictably go up when the other went down, now
they both go down together.) It all points to the very real likelihood that
the overall marine biomass has been depleted (and not entirely by "warm
water" ;>)

"The many errors?" - I wish you'd been more precise. Is it an error by
definition to ask new questions? - to make new observations or

What I would like to read, but have been unable to find - maybe you can
help me - is research done on the possibility of undernutrition as a
contributing factor in mass coral bleaching. Experiments that provide
supplemental feeding to test corals, to check whether or not the possession
of increased stored reserves confers any advantage in resisting "warm water
coral bleaching." Has this been done? 

And how do you explain the "patchiness" of bleaching occurring on a given
reef? Relating it to feeding success is maybe a plausible idea, since
corals are immobile and at the mercy of the random availability of the
"patchy" food that may come their way - all similar corals will therefore
not necessarily have equal feeding success or energy stores for the lean
(warm) times. 

  In contrast - extensive experimental and field
>evidence (as opposed to weakly based conjecture) exists of temperature as the
>primary factor (and light as an important secondary factor).  

Yes, believe it or not I've read a fair amount of that. The fact that
bleaching is strongly associated with warm water spells is not inconsistent
with the idea that an important factor could be low nutritional stores. The
predominance of events in warmer water would be expected. It's all in where
your suspicions lie - and there's been a lot of attention to the suspicion
of warm water as cause - but, as they say, "you'll find what you look for,"
which is true to quite an extent, and you won't find what you don't look
for. If you're going to cover all the bases in making the complete correct
diagnosis, you need to consider the possibility of food-starvation. It
should be relatively easy to rule out - no? Maybe it's an unnecessary test,
but it's in the best interest of the patient to run all the tests anyhow,
"just in case." "Unlikely" maybe, but I thnk it's best to rule it out, and
I've yet to see where it has been considered.

>I have sent you a copy of reviewed material that should help you in your
>research.  Perhaps this will help you understand the errors you have made.
>then - feel free to come back to me with any questions you might have.

Yes, thanks, I've read it already. And I have another question. Figure 10,
your long-term sea surface temp data, shows the thermal thresholds for
corals in the 3 regions of the Great BArrier Reef : south approx 28.2 C,
central approx 29.2, and north approx 30. And corals in all three areas
have been recently affected by the warm-water bleaching, the difference in
their tolerances is due to each being acclimatized to the normal temps
where they are. It looks like the mean temp in the central area has
recently risen from about 27 to almost 28, and that area is not hitting the
"30 threshold" at all, the temp limit that the northern cousins can't take.
But the northern ones lived quite comfortably in the past at a mean temp of
28. Have you tried transplanting any corals to more southerly locations,
where conditions might now match what they were used to for so long? It
would be interesting to see if the naturally more heat acclimatized ones
would have better survival these days if moved a bit south. If so, it
strengthens the "temp threshold" theory, you've spared them from the temp
peak that they cannot tolerate...if not, it might  point to the possibility
of the "starvation" theory.

Earlier you wrote:

>I find the idea pretty hard to rationalise over the extent of areas seen
in the
>1997-98 bleaching cycle.  While it may contribute to a varying threshold like
>other factors, I doubt whether it is the cause.  Warming oceans is the main

"Doubt?" "hard to rationalize?" -- OK, sure, it's hard to "get your head
around the possibility" -- but it's not something that will be particularly
hard to test for. 

The temperature-based research was probably stimulated by an observation
like "There seems to be a lot of unusually high temperatures lately, it's
getting warmer, I wonder if that's hurting these corals."  Where I'm
"coming from," however, is noting what looks like poor feeding, slowed
growth and reduced fat content and reproductive success in a very wide
range of organisms throughout the ailing ocean -- so for me, coral
bleaching prompted the question "I wonder if the sick corals are
experiencing feeding difficulties as well?"

Another question: Do you believe that the sewage, etc., that we've poured
into the rivers literally serves as an effective replacement,
nutrient-wise, for the fish that we've removed? Or, do you think that it
doesn't matter...that "there's lots of other fish in the sea?"

And one of my other "odd conclusions" - "the importance of solid vs liquid
nutrients" - what do you think about that one? I think that the reefs
cannot tolerate high levels of "liquid nutrient," but clearly tolerated
high levels of "solid nutrient" prior to fishing...and would incorporate
solid nutrients into their food web today in a non-damaging way, if such
nutrients were made available. 

Debbie MacKenzie

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