[Coral-List] Bleaching and sponge disease in Tobago.

marie smedley marie_smedley at hotmail.com
Sun Oct 3 14:36:30 EDT 2010

Volunteers at the Coral Cay project site in
Tobago have been surveying the Atlantic and Caribbean sides of the northern end
of Tobago and over the past month we have been monitoring the current mass-bleaching
event. Coral Cay initially came to Tobago in 2005 to monitor the recovery
process of the mass-bleaching event at the time. Results from 2005 till now indicated  that many of the popular dive sites on
the Caribbean side of Tobago such as Buccoo Reef and Mt. Irvine saw a significant
drop in coral cover (±50%) as a consequence of the bleaching event and the
disease outbreaks that followed. Speyside is one of the most biodiverse and
popular dive sites currently in Tobago and is located on the Atlantic side. It is
considered one of the most robust coral reef sites in Tobago and was only marginally
affected by the 2005 bleaching event. What is of concern is that now Speyside
appears to have been heavily impacted by the current bleaching event with some
sites approaching near to 100% bleaching according to our surveys, whilst the
Caribbean side appears to be relatively less impacted. The associated
temperatures have been around 30-31 degrees in heavily impacted survey sites in
Speyside whereas on the Caribbean side associated temperatures have been 27-29
degrees Celsius. A high variety of corals, gorgonians and zoanthids were found
to be bleached at all survey depths including 16, 12, 7 and 2m and have been
seen to be bleaching deeper than this.

What is also of concern is that the bleached
sites are impacted by an outbreak of an unknown sponge disease. Coral Cay surveyors
have witnessed countless barrel (Xetospongia
muta) and yellow tube sponges (Aplysina
fistularis) at Black Jack Hole, one of the more popular dive sites in
Speyside, degrade to mush in less than a month. 


It would be greatly appreciated if fellow
coral-listers communicate if they have noticed other sponge species being
affected. It is unknown if the disease is the same between species. Barrel
sponges seem to exhibit a gradual bleaching like process from the inside that
breaks down to the base. Yellow tube sponges have been in various stages
including being covered in regular 'bite mark' shapes that may be progressing
into general degradation. 


Attempts are currently being made to take
samples to establish the cause and to also compile a photo library to look at
the different stages of the sponge disease. Other details and images would
therefore be appreciated.  The
worst hit areas for bleaching are also experiencing the highest level of sponge
disease and degradation suggesting an associated cause. It is important that
efforts are made to establish the cause as currently no predictions can be made
as to the prospective spread and future occurrence of the disease. 


So far, no sign of recovery has been noted
in the Speyside region, which is to be expected with the consistently high
water temperature. Recent surveys have shown extensive mortality of white
encrusting zoanthids, encrusting gorgonians and common sea fans.


If you’re interested, you can find updates
in our monthly project updates on the website (www.coralcay.org) 


Any more information regarding the presence
of sponge disease and bleaching within the Caribbean would be appreciated to
assist in the monitoring of this event. Additionally, we call on volunteers to
assist us with the monitoring project.


Kind regards


Marie Smedley

(Project Scientist)
TRCP at coralcay.org+1868 304 1802

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