[Coral-List] fish and algae

Martin Moe martin_moe at yahoo.com
Wed Feb 19 09:46:13 EST 2014

Pertinent to this discussion I think it is important to
point out that the basic ecology of the coral reefs in the western tropical
Atlantic changed rapidly and dramatically with the demise of the Diadema sea
urchins. These herbivorous urchins were critically important in maintaining the
balance between the growth of coral and macro algae. Before 1983, I doubt that
damselfish could maintain lawns in areas accessible to the grazing activity of
Diadema. The return of Diadema to the coral reefs of this vast area is
essential to the ecological restoration of these reefs. This might happen
naturally over time spans measured in numerous human lifetimes, or more rapidly
if we can enhance Diadema populations on these reefs though breeding and
replacement programs. The work of Tom Capo, Alina Szmant, Margaret Miller, Dave
Vaughan, and myself in this effort demonstrates that this is not an impossible
dream, difficult, yes, but not impossible.. With proper funding, personnel, and
facilities it can be done.

Martin Moe

On Wednesday, February 19, 2014 7:54 AM, 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.


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
nicrane at cabrillo.edu

Oceanic Society
Senior Conservation Scientist

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