[Coral-List] fish and algae

Dennis Hubbard dennis.hubbard at oberlin.edu
Tue Feb 18 10:07:44 EST 2014

Thanks Bill:

I am familiar with Peter's excellent work and he was one of the folks I
referred to in my email.I will, however, go back over this paper. If you
have anything else that discusses the interesting relationship with post
COTS and bleaching/disease outbreaks, I'd love to read these articles. In
particular, if someone has published a more recent review that either
embraces or refutes the "Damselfishes are thugs" idea, I'd love to assign
in as a class reading.

I will be very interested to see what folks have to say on this as I teach
a class to mostly non-majors. My job is to take some of the complex
scientific discussions that are nuanced by elements that only those close
to the field might understand. So, if there has ben a paradigm shift
regarding the relative role of algal turfs as primary producers versus
coralline algae as binders versus macro-algae as a nuisance that nobody
eats - and the fish who eat/control them in various ways, I'd like to
understand this so I don't pass on bad information (my post was a real
question with no other agenda). So, anyone who has information on whether
our ideas on these interactions plus the roles of nutrients, sediment and
grazing - please chime in. I'm looking to be educated if the landscape has
changed on this issue. Hopefully folks who do know something about this
will recognize that this is the audience we talk about all the time on this
site - so we should be worried about getting this right.



On Tue, Feb 18, 2014 at 8:07 AM, Bill Allison <allison.billiam at gmail.com>wrote:

> Hi Dennis,
> No doubt damsels kill coral. As you suggest, it is most likely that
> underlying causes such as bleaching, pollution, and overfishing tilt the
> playing field too allow more coral destruction, or less construction, or
> both, but it's much more satisfying spiritually and economically to have a
> critter to blame and kill, non?
> On several reefs that I have surveyed over time corals survived only in
> Stegastes nigricans territories after repeat COT outbreaks (I also noticed
> coral survival in damsel territories after the 1998 bleaching). During the
> second COT outbreak all the preferred COT prey were gone and the COT were
> eating whatever was left. Some coral colonies within but near the periphery
> of S. nigricans territories were damaged along their outer edges but apart
> from that, corals in S. nigricans territories survived these invasions
> unscathed. I am not the first to have noticed this (e.g., Glynn and Colgan,
> 1988)
> Glynn, P. W. and M. W. Colgan (1988). "Defense of corals and enhancement
> of coral diversity by territorial damselfish." Proc. 6th ICRS, Townsville
> 2: 157-164.
> On Sun, Feb 16, 2014 at 5:56 PM, Dennis Hubbard <
> dennis.hubbard at oberlin.edu> wrote:
>> When I was a young reef geologist, I was told by most biologists visiting
>> West Indies Lab that Damselfish "farm" the algal turfs and actually crop
>> them for maximum yield. As such, they help maintain this autotrophic
>> system
>> which transforms organic carbon and nutrient into a form (algal tissue)
>> that can work its way up the food chain. Walter Adey used turfs to
>> maintain
>> balance in his "microcosms" at the Smithsonian, has been a valued
>> consultant to aquaria (including the large GBR tank) and has received
>> patents for "algal scrubbers". So my sense was that the service provided
>> by
>> both the turfs and the fish that regulated them is still recognized.
>> I was just looking for photos to shamelessly use for class and came across
>> an NPR piece (*Tiny Damselfish May Destroy a Ree*f) dated August 11 in
>> which Richard Harris (who regularly appears on *Morning Edition* and *All
>> Things Considered*) described a "war going on between corals and 'a
>> creeping menace'.... algae". This crux of the story is that parrotfish are
>> the "allies of coral" and 'damselfish promote algal growth by killing
>> coral
>> to create new space for algal colonization'. Enter the fishermen who have
>> taken out the predators who used to "keep the damselfish in check". The
>> result is that damselfish are disproportionately opening up more space by
>> killing corals while scaring off the "coral-friendly" parrots by shear
>> tenacity.
>> Might anyone put this into perspective for me so I don't tell a story that
>> is no longer true? Each of these points has a ring of truth... overfishing
>> is real and algae can inhibit coral recruitment. However, the
>> transformation of damsels from fish "tending their gardens" to "the
>> primary
>> ally of the creeping manace" seems a bit dramatic. It also seems to
>> conflate algal turfs (which I understand the damsels are cultivating) and
>> macroalgae (which can be equally damaging to both corals and turfs by
>> shading and a host of other pathways).
>> As I hope to get to this in about a week in class, I'd appreciate it if
>> folks who are closer to this can give me a sense of whether eradicating
>> algal turfs and the scurrilous damselfish that encourage them is the new
>> reef paradigm. If there is a place I can send a smart undergraduate (not
>> necessarily a NS student) to read about this new balance, that would be
>> even better. What I have read has argued that there are ties between
>> macro-algal proliferation and both overfishing and increased nutrient
>> input. While there have been numerous thoughtful discussions about the
>> details of these interactions, I have understood that both of these
>> possible linkages are are still considered to act at some level. I can
>> also
>> imagine a delicate balance between the benefits of encouraging turfs and
>> clearing space by chomping on live coral.... and that fishing has impacted
>> this. My question is whether situation portrayed in this NPR interview is
>> correct and that the damselfish/turf ralationship shas gon awry to the
>> point that we need to stop worrying about lionfish and focus on what I
>> agree is, "pound-for-pound", the meanest fish on the reef.
>> Dennis
>> --
>> Dennis Hubbard
>> Chair, Dept of Geology-Oberlin College Oberlin OH 44074
>> (440) 775-8346
>> * "When you get on the wrong train.... every stop is the wrong stop"*
>>  Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"
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> --
> "... the earth is, always has been, and always will be more beautiful than
> it is useful." - Ophuls, 1977

Dennis Hubbard
Chair, Dept of Geology-Oberlin College Oberlin OH 44074
(440) 775-8346

* "When you get on the wrong train.... every stop is the wrong stop"*
 Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"

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