[Coral-List] fish and algae

[Dennis Hubbard]

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*"