[Coral-List] Giant barrel sponges taking over Florida's reefs!

Vassil Zlatarski vzlatarski at gmail.com
Wed Sep 2 04:25:15 EDT 2015

Dear Coral-Listers,

Prof. Pawlik offered interesting paper “Population dynamics of giant barrel
sponges on Florida coral reefs” and video adding to the growing evidence
that reef-building corals are declining and sponges are becoming the
dominant inhabitants of modern Caribbean benthic communities.  For the
fortunate researchers of coral reefs 4-5 decades ago is strange the usage
of “coral reefs” for the documented now-existing situation.  Is it not in
reality a case of “sponge gardens”?



Vassil N. Zlatarski

D.Sc. (Biology), Ph.D. (Geology)

On Tue, Sep 1, 2015 at 10:45 AM, Pawlik, Joseph <pawlikj at uncw.edu> wrote:

> Greetings, Colleagues,
> In a 12-year study just published in the Journal of Experimental Marine
> Biology and Ecology, we report that populations of giant barrel sponges
> have increased by 122% since 2000 on Conch Reef, off the coast of Key
> Largo, Florida. This adds to the growing evidence that sponges are becoming
> the dominant inhabitants of modern Caribbean reefs.  The article can be
> downloaded for free:
> http://authors.elsevier.com/a/1RcjD51aUK0hE
> Giant barrel sponges (Xestospongia muta) are found throughout the
> Caribbean, and commonly grow to the size of an oil drum or larger. Called
> the "redwoods of the reef," these sponges can live to be hundreds, even
> thousands of years old, based on earlier growth studies conducted by the
> same first author, Dr. Steven McMurray.
> A video tour of the plots on Conch Reef can be seen here:
> https://youtu.be/qdjhm7ojGJk
> You can see how large these sponges get in this video from the Bahamas:
> https://youtu.be/8WaWVuGE-LM
> Not only are the numbers of giant barrel sponges increasing, so is their
> volume, with a 39% increase since 2000. On average, each square meter of
> Conch Reef now has about 2 liters of barrel sponge tissue on its surface,
> more than any other organism on the reef.  And the giant barrel sponge is
> only one of many species of sponges that populate Caribbean coral reefs.
> Much of the increase in the numbers of giant barrel sponges was due to
> recruitment - the successful establishment of baby sponges. On some plots,
> the increase in the smallest-sized barrel sponges was over 600% for the
> period 2000-2012. And while the survival of larger barrel sponges was
> stable for the first half of this period, it increased during the second
> half, perhaps because of the absence of hurricanes over that time period.
> When hurricanes pass over reefs, large sponges can be damaged and
> dislodged, often resulting in mortality.
> Regards,
> **************************************************************
> Joseph R. Pawlik, Professor,
> Dept. of Biology and Marine Biology
> UNCW Center for Marine Science
> 5600 Marvin K Moss Lane
> Wilmington, NC  28409
> Office:(910)962-2377; Cell:(910)232-3579
> Website: http://people.uncw.edu/pawlikj/index.html
> PDFs: http://people.uncw.edu/pawlikj/pubs2.html
> Video Channel: https://www.youtube.com/user/skndiver011
> **************************************************************
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