[Coral-List] fish and algae

[Steve Gittings - NOAA Federal]

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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>



-- 
Dr. Steve Gittings, Science Coordinator
NOAA Office of National Marine Sanctuaries
1305 East West Hwy., N/ORM62
Silver Spring, MD  20910
(301) 713-7274 (w), (301) 529-1854 (c)