[Coral-List] fish and algae

Dennis Hubbard dennis.hubbard at oberlin.edu
Wed Feb 19 09:46:37 EST 2014


Wow! Great observations. Thanks so much!!

What I have learned from this back-and-forth is that we are talking about a
very nuanced relationship that changes with the relative supremacy of
ancillary players. Eventually, we will probably move onto the "what do we
do about it" phase of the discussion, but I really hope to see more
observations and ideas regardless of how robust the contributors might feel
their observations are. My reading at this point is that this relationship
is different in different places and different in individual perceptions
and observations. At this point, I have no idea where this discussion will
end up, but for me it has been one of the more satisfying discussions I've
had because I'm actually learning something about a topic that I thought
I'd figured out long ago.

Perhaps the message is that "scientific" truth changes with time. I'm not
quite sure why I'm having so much fun demonstrating how much I don't
understand something, but thanks to all who have contributed observations
to the thread. Unless I hear from someone that they'd like to remain
anonymous to my students, I'd like to share these contributions with
my *Biology,
Geology & Politics of Coral Reefs* class. I think this is a great
demonstration of how science should work.


On Tue, Feb 18, 2014 at 6:21 PM, Nicole Crane <nicrane at cabrillo.edu> wrote:

> This is a great discussion, and I felt inclined to weigh in.  We've been
> surveying reefs in Micronesia, and while we have quantitative data sets,
> we didn't look specifically at damselfish, so I'm afraid I have no
> empirical evidence for the following observation (other than having
> looked at many reefs):
> The 'healthiest' reefs we see (high coral morphology diversity, high
> cover, high biomass and diversity of fish etc.), are places where I see
> damselfish (on shallow flats) and their 'gardens'.  The more degraded
> reefs seem to have far fewer of them (I'll mention that Acropora is
> harvested from some reefs for the lime that is chewed with beetlenut).
> Not that this bolsters any specific argument, but I am reminded of how
> we need to be careful to make sensational, simplistic stories from a
> complex stage.  I am reminded of the African Elephant who has long been
> blamed for their destructive eating habits and the negative impacts on
> acacia trees (an ecosystem disservice?).  Yet, by eating the seed pods
> of certain acacias, they sterilize the seeds, protecting them from
> certain death from a parasitic grub that will otherwise kill them.  Upon
> defecation on to the fertile grassland soil, a very high percentage of
> these seeds will germinate (an ecosystem service?).
> Thus the charismatic mesofaunal damselfish (to distinguish it from the
> marine megafaunal superstars) probably has a complicated story behind
> it.  Steve said it well!
> Maybe its our responsibility in part to make sure that when these
> stories are told in a public forum, simplification and sensationalism is
> really not necessary - the whole story is really the interesting one.
> Nicole
> On 2/18/14, 10:34 PM, Steve Gittings - NOAA Federal wrote:
> > Dennis,
> >
> > Interesting observation.  Perhaps the essence of the "delicate balance"
> is
> > that, when an ecosystem has it, the natural state enables the ecosystem
> > service  - predators keeping damselfish in check, allowing those
> surviving
> > ones to tend gardens while keeping  few corals out.  It still leaves
> plenty
> > of space for other species and interactions, each of which provides its
> own
> > services.  When out of balance, the natural behaviors, which of course
> > continue, turn what had been an ecosystem service into what can only be
> > considered an "ecosystem disservice" - high damselfish populations
> > inhibiting corals and promoting algae.  In this case, the problem is
> > exacerbated not only by overfishing, but by the *Diadema *dieoff.
> >
> > sg
> >
> >
> > 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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> >>
> >
> >
> --
> Nicole L. Crane
> Cabrillo College
> Division of Natural and Applied Sciences
> 831-479-5094
> nicrane at cabrillo.edu
> www.cabrillo.edu/~ncrane
> Oceanic Society
> Senior Conservation Scientist
> www.oceanicsociety.org
> _______________________________________________
> Coral-List mailing list
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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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