[Coral-List] Tunicate-killing coral spreading all across Caribbeanregion

Robert Miller rjmiller1 at gmail.com
Tue Jan 22 20:06:14 EST 2008

I think that post-settlement mortality by competition and other factors, eg
predation and sedimentation, while settlers are still very small, probably
accounts for most mortality of sessile invertebrates like this ascidian.
Therefore, one need not look for a predator of adult ascidians that
previously controlled  this species, but rather a predator, competitor, or
disturbance that killed the very small ones.  Urchins could be one factor,
through bulldozing as well as predation.  In the North Atlantic there are a
couple of invasive species of colonial ascidian that are able to dominate
large areas on horizontal surfaces because they seem to be able to overcome
competition for space with algae, sedimentation, and perhaps other factors
that limit most native species to vertical or undercut surfaces.  They seem
able to do this through rapid growth and resistance to algal competition,
although one species at least, and probably both, are resistant to urchin
grazing.  The small recruits may also be resistant to micropredators.  It
might be interesting to compare the growth rates or this species in areas
where it is and is not overgrowing coral, and to compare rates of
postsettlement mortality.
Bob Miller

On 1/21/08, Christine Schoenberg <christine.schoenberg at uni-oldenburg.de>
> Dear Tom,
> On Jan 17, 2008, at 7:03 PM, Thomas Goreau wrote:
> > Dear Andrew,
> >
> > Thanks,. I do recall a paper on Hawksbill sponge feeding preferences
> > some time ago (and not just Xestospongia muta), but have lost track
> > of the reference, and sponge and turtle people I ask don't seem to
> > know about it. Anyone out there know?
> Try:
> MEYLAN, A.B. 1988. Spongivory of hawksbill turtles: a diet of glass.
> Science 239: 393-395.
> Meylan A (1990) Nutritional characteristics of sponges in the diet of
> the bawksbill turtle, Eretmochelys imbricata. In: Rützler K (ed) New
> perspectives in sponge biology. Smithsonian Institution Press,
> Washington, pp 472–477
> Van Dam, R. & C.E. Diez. 1997a. Predation by hawksbill turtles on
> sponges at Mona Island, Puerto Rico. In: Proceedings of the 8th
> International Coral Reef Symposium 2: 1421-1426.
> Vicente, V.P. & N.M. Carballeira. 1991. Studies on the feeding
> ecology of the hawksbill turtle, Eretmochelys imbricata, in Puerto
> Rico. In: Salmon, M. and Wyneken, J. (Compliers). Proceedings of the
> 11th Annual Workshop on Sea Turtle Biology and Conservation. NOAA
> Technical Memorandum NMFS-SEFSC-302. Miami, Fl. pp. 117-120.
> Diet of East Pacific Green Turtles (Chelonia mydas) in the Central
> Gulf of California, Mexico
> Jeffrey A. Seminoff, Antonio Resendiz, Wallace J. Nichols
> Journal of Herpetology, Vol. 36, No. 3 (Sep., 2002), pp. 447-453
> College, 1998. A thesis submitted in partial fulfillment of the
> requirements  for the degree of Master of Science  in the Department
> of Biology  in the College of Arts and Science  at the University of
> Central Florida Orlando, Florida
> Troeng, S, Dutton, PH, Evans, D 2005. Migration of hawksbill
> turtles... Ecography 28: 394-402
> Bjorndal KA (1980) Nutrition and grazing behavior of the green turtle
> Chelonia mydas. Mar Biol 56: 147–154
> Bjorndal KA (1990) Digestibility of the sponge Chondrilla nucula in
> the green turtle, Chelonia mydas. Bull Mar Sci 47: 567–570
> Eckort SA, Eckort KL, Ponganis P, Kooyman GL (1989) Diving and
> foraging behavior of leatherback sea turtles (Dermochelys coriacea).
> Can J Zool 67: 2834–2840
> Hartog den JC (1980) Notes on the food of sea turtles: Eretmochelys
> imbricata (Linnaeus) and Dermochelys coriacea (Linnaeus). Neth J Zool
> 30: 595–610
> Cheers, Christine
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Robert J. Miller
Santa Barbara Coastal LTER
Marine Science Institute
University of California, Santa Barbara
Santa Barbara CA 93106-6150
(805) 893-7295

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