[Coral-List] Parrotfish loss drives reef decline
riskmj at mcmaster.ca
Wed Feb 15 10:23:25 EST 2017
I hesitate to weigh in here, but I thought I would offer some random
The Kramer et al. paper is a very nice piece of work, using up-to-date
techniques (some of which are beyond my limited comprehension). My
compliments to the authors.
None of us should be surprised by verification of the importance of grazing
in reef systems. Personally, I think that ever since Stephenson and Searles,
Odum and Odum, Gerry Bakus and Kaneohe Bay, the vast majority of coral reef
research has simply been fine-tuning what we already know.
There are some aspects of the paper that are worth considering further.
First of all, few people in this world have looked at more well core than
have Gene, and he notes that abundance estimates from teeth must be taken
with a grain of sand (forgive me). I note that cores were taken by "a
combination of push-coring and vibra-coring", which produces large,
relatively undisturbed samples but means that you cannot core reef
framework. Authors are to be commended on their good dating techniques (age
reversals can be used as a proxy for storm transport, which might have been
worth noting), and one of their three sites records information of the time
scale of most interest to us: post-1900 (but there the resolution tails off
This new (to me) CCM technique for teasing out causality seems to be a
powerful tool, but I note it works if you only consider two variables: as in
this case. Of course, nutrient proxies would have been difficult to
obtain-but nonetheless possible.
Personally, I am not surprised at the lack of correlation with Diadema. If
we look closely at Gardner et al., we see that the precipitous decline in
Caribbean reefs began prior to 1960. The dieoff in populations of Diadema is
in no way reflected in that decline-the line continues its sad progress
without a blip.
My concern here is that there may be a tendency to apply these results to
rehabilitation efforts, and concentrate on bringing back the fish. It is my
impression that people with a mostly biological focus tend to believe that
reefs will recover if the grazers come back, whereas those with a more
varied background in chemistry and geology take a more nuanced approach.
As far as I know, there is only one example from the Caribbean of the
response to an increase in water quality. No one should be surprised to
learn that the reef came back. Equally, no one should believe the reefs will
come back if only the grazers come back.
riskmj at mcmaster.ca
1. mailto:riskmj at mcmaster.ca
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