New Killer Disease Attacks Giant Barrel Sponge

Submitted by Mito Paz

"A new killer is ravaging sponges on the Belize Barrier Reef. This mysterious disease decimates the giant barrel sponges (Xestospongia muta), which grows on the fore-reef and drop-off and can reach a width of six feet. A giant barrel sponge can grow to be 100 years old.

The disease was first found by Changa Paz of Amigos del Mar, a member of the San Pedro based organization Green Reef, in the late summer at Vicent Point, Turneffe Islands. 'We might have another disease on our hands. Remember the coral bleaching from last year? Now we have a disease that is killing the barrel sponges,' Changa said. Paz is also credited with the discovery of the coral bleaching on the reef off Turneffe Islands.

Not much is known about the disease. We have no idea what causes this disease, whether it is a bacteria, fungus or virus, but the effects are clear: the sponge starts to bleach from the base up until the whole sponge is completely white and then it just crumbles apart. It takes about two weeks for the disease to completely kill a giant barrel sponge. Under strong current conditions, the sponge breaks from the base and collapses. What is left behind is a large bare rock with no growth where the sponge was previously attached to the substrate.

With all these new diseases popping up, one must ask if there is there a general increase of marine pathogenic organisms (bacteria, fungus or viruses) that are impacting the reef environment? What caused the sea urchin wipe-out? Why are coral diseases on the rise? What is ripping through the sea fans? Are sponges being affected by these pathogens?

These are a lot of unanswered questions. Until we learn to be good citizens of the earth and stop taking the reef for granted, Belize might lose one of its most important natural resources."

Mito Paz has also been corresponding via email with interested individuals and groups and has received reports of similar sponge problems at Key West, Florida.

Mr. Paz also provided the following article on coral bleaching:. (Editor's note: When coral polyps eject, or vomit the algae they feed on, they lose the nutrients contained in the algae that feed the polyps and give them their vibrant clours. This nutrient loss starves the coral, leaving it white and lifeless, a phenomenon known as bleaching.)

The 1995 coral bleaching event in the western Caribbean was the first that significantly affected the Belize Barrier Reef. The bleaching was attributed to a two month period of warm water temperatures between 32 and 34 degrees in shallow back reef areas. Near Ambergris Caye, barrier and patch reefs along the coast experienced up to 50% bleaching. At Mexico Rocks Patch Reef Complex (MRPRC), important changes in reef health, community and physical structure occurred, probably owing to the 1995 bleaching event.

During the years 1988-1993, 23 patch reefs of the MRPRC were mapped, geologically analyzed, and ecologically surveyed. The zone was characterized ecologically and taxonomically as a stony, head coral complex. MRPRC consisted of 83% healthy, well-colored, framework-building head corals. Other reef-building taxa and reef dwelling, invertebrate taxa were of secondary importance. During this interval, the MRPRC exhibited 24% degradation of reef surfaces and 5.3% cavity development.

22 of the MRPRC patches were resurveyed in March 1996, after the bleaching event. Less than 1% of the complex is currently experiencing bleaching. Comparison of the pre- and post-bleaching degradation values indicates that degradation increased and coral cover decreased 13%, indicating high coral mortality. The secondary disturbances that can follow coral mortality associated with a bleaching event are present in the complex, including an increase in algal cover and subsequent herbivory that erodes the reef framework. The full impact of this bleaching event may not be concluded for years, and may have implications for interpretation of reefs in the fossil record.




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