[Coral-List] Let's not forget the bigger ecosystem
dennis.hubbard at oberlin.edu
Wed Feb 15 18:29:46 EST 2017
Excellent points. My recollection for the Caribbean 'model" was that, as
the parrotfish were eaten off the reefs, *Diadema* was picking up the
slack, but the Queen Triggerfish was keeping them in check. While not a
favored food fish, once other options were removed, the QT declined
rapidly, allowing the *Diadema* to go wild. Again only a recollection, but
some had even postulated that this was a boom-and-bust scenario for
*Diadema* - except for that pesky microbe that appears to have come through
the Panama Canal. Certainly this is not at the large scale you are
advocating. However, it was a start. The fact that folks went from the
fish/urchin vs algae relationship to a paradigm in which fish/urchins and
coral abundances were intimately tied together illustrates how little we
probably do understand all of this. Fortunately, as a geologist, I only
have to think about how much they scrape, bore and grind from the reef
edifice and don't have to understand the subtext behind the main play.
On Wed, Feb 15, 2017 at 1:29 PM, Tim McClanahan <tmcclanahan at wcs.org> wrote:
> I often find the sea urchin - parrotfish - nutrient focus of many coral
> reefs studies to lack the bigger ecosystem-environment picture. We each
> measure and bring in our own interests and interpretations based on our
> disciplinary foci. One of my main foci has been top-down controls and the
> larger food web interactions within environmental contexts. Sea urchins
> and parrotfish exist in a larger food web and so it is always challenging
> to conclude about their ability to control the ecosystem without looking at
> their position in the larger food web-environment.
> I think the work in the Caribbean suffers from this limited foci problem
> too often. I rarely hear Caribbean coral reef scientists on this list who
> study and quote any work on the predators who control parrotfish and sea
> urchins apart from humans. Certainly these functional groups are part of
> the larger food web, so they must have their own influences and not be
> isolated or controlling independently of impacts on their own populations.
> Is this ecosystem-view just too complicated and difficult to study and
> understand? Regardless, I hope reef scientists might make a better effort
> to study the larger system when possible.
> In case readers are interested, the paper published open access in the link
> below looked at many possible controls on calcifiers in the Indian Ocean
> and concluded the extreme temperatures and the red-lined triggerfish were
> probably having strong and equal effects on the calcifying community.
> There were no effects of Diadema or parrotfish but a role of Echinometra
> via it's interactions with it's main predator - Balistapus undulatus.
> Can these regional difference be explained away as another region or
> system? Or could work in other systems lack this larger ecosystem
> perspective and therefore coming to parochial conclusions? We won't know
> until the larger ecosystems are studied in all regions and compared. I
> think much critical work needs to be done..
> Tim McClanahan, PhD
> Senior Conservation Zoologist
> Wildlife Conservation Society
> Coral Reef Conservation
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