[Coral-List] Bleaching Surveys

[Jim Hendee]

  [I am forwarding this for Dr. Ernesto Weil, who was apparently having 
problems sending this because the address he sent it from was not his 
subscribed address <eweil at caribe.net>.]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

From:  Ernesto Weil <reefpal at gmail.com>
 
Dear Colleagues, I have sent this note four times in the last weeks but 
it does not get to the list somehow. It has been rejected three times by 
the administrator, I believe tjhis has to be a system problem, so I send 
it directly to Jim so he can post it.   

We just finished our disease-bleaching surveys in Bermuda and Grand 
Cayman. No bleaching was observed in Bermuda. GCayman still had a few 
totally bleached colonies of /Montastraea franksi/ and /Agaricia 
lamarcki / down to 140 feet. All bleached colonies were still alive and 
no mortality was observed. In shallower habitats, colonies of several 
species are recovering their coloration.
 
 From our travel and information gathered this summer and up to early 
December, the only areas not affected by an intensive bleaching were 
in the south-central Caribbean including the Netherland antilles 
(Curacao, Bonaire, Aruba) and northern coast of Venezuela. Fortunately, 
these are some of the best and most diverse reefs in the Caribbean. 
Recently however, Steve Piontec from the Aquarium in Curacao and 
colleagues from the Universidad Simon Bolivar in Venezuela, reported 
that minor bleaching, with mostly paling colonies, in reefs off Curacao 
and the northern coast of Venezuela was observed. Grenada, Barbados and 
Tobago on the the south-east had substantial bleaching from our 
observations and reports in the list. Near shore reef areas in the 
northern coast of Colombia seem to have experienced minor bleaching 
also. From Panama to Mexico bleaching was intensive and extensive as in 
the northern Caribbean as you all know from the reports in the coral 
list. Corals are now recovering their coloration in most areas. 

Here in La Parguera, Puerto Rico, observations from the last two weeks 
indicate that most large colonies of /Montastraea, Diploria, 
Colpophyllia/, /Dendrogyra,/ and /Siderastrea /are showing coloration 
recovery starting from colony edges with some large colonies with 
colored patches all over. Many colonies still remain white. Some groups 
had curious bleaching patterns ( /Porites astreoides/ bleached in 
shallow and deep areas mostly but not at intermediate depths). 
Most colonies of species that rerely bleach, bleached this year and are 
still pretty much white or pale (/Mycetophyllia, Mussa, Scolymia, 
Isphyllastrea /, etc).   

The sad news, is that high mortalities of /Acropora palmata, //A. 
cervicornis and Millepora spp. / have been observed in shallow areas of 
three reefs. Partial mortality is common but many colonies are totally 
dead. Some /A. palmata/ are showing signs of white band disease 
underneath the colony branches, but most of them are bleached or showing 
signs of necrosis and tissue "sloughing off" or "dislodging" from the 
skeleton in most branches (shut down reaction??), even tissue that is 
still colored is sloughing off. These colonies were doing great for 
several years, surviving bouts of patchy necrosis and three 
other bleaching events since 1998 until tgis year. In most 
shallow habitats, all large stands and individual colonies of /Millepora 
complanata/ and /M. alcicornis/ are dead and already covered by fine 
filamentous turf algae. In the deeper reef habitats of inner and 
mid-shelf reefs, high mortality of the platy /Undaria humilis /and /U. 
purpurea/ was also observed. 

As to exactly what caused the mortalities, there is no doubt that the 
bleaching was part of it, but there are confounding factors that might 
have exacerbated the impact. We had many days of heavy rains in the last 
months (unusual for this area) which have lowered salinity levels in the 
first 1-2 meters of the water column, lots of sediments coming from the 
run-off waters and rivers upstream have also washed out to the reefs. In 
late November, trade wind activity was high and even though the water 
temperatures are coming down, heavy seas and surge are resuspending fine 
sediments from the bottom. Visibility has been down to a couple of 
meters in most reefs up to 3-4 km. offshore for two weeks now. TD 
27 produced more surge and rain. We'll keep monitoring these reefs and 
individually tagged colonies. . 

Saludos!

EWeil