[Coral-List] Bleaching in Venezuela

[Sebastian Rodriguez]

Hollow listers,

In Cayo Sombrero (Morrocoy National Park, MNP Venezuela) we observed that
bleaching did not occur at the maximum SST of July-September, but a month
later, similarly to the report made to the coral list by G. Díaz et al. for
Santa Marta, Colombia (fecha). In this case, however, we have not identified a
mechanism such as upwelling, that helps to explain this delay between maximum
temperature and bleaching.

Between the 23rd of september and the 4th of october of 2005, during the annual
surveys of the GCRMN and CARICOMP, we examined five reefs, two oceanics, at Los
Roques Archipelago National Park and three continental reefs at MNP. We surveyed
more than 500 colonies between 5 and 12 m depth, and only two colonies were
partially bleached (< 5% of their surface).  Sea surface temperature (SST) was
30 °C.

By the end of october, SST was also 30 °C but we found that 21 ± 4% of the
colonies (n = 5 transects) had bleached in Cayo Sombrero (CS) at MNP. Most
affected species were: M. franksi (50%), M. faveolata (31%), C. natans (15%),
M. meandrites (100%), A. agaricites (67%) and hydrocorals Millepora spp (38%).
Of the bleached colonies, 19% were afected in < 10% of their surface, 5% were
afected in 10-25% of their surface, 19% in 25-50% of their surface and 60% of
the colonies were bleached in 75-100% of their surface. We also observed
bleached.colonies of  D. strigosa, M. cavernosa, P. astreoides, C. natans, D.
laberyntiformis outside those transects.

By the 13th of november, the SST had dropped to 28.7 °C but qualitatively we
observed more colonies bleached than the previous two weeks and it seemed more
intense in terms of colony whiteness.  Thus, in CS bleaching did not occur at
the maximum SST in july-september, but a month later.
We will keep monitoring this event and hope to report the recovery of the
colonies in the next weeks.

Best wishes,

Sebastián Rodriguez
Denise Debrot
Adriana García
Carolina Bastidas

-- 
Sebastian Rodriguez
Lab. Comunidades Marinas,
Ecotoxicologia y Contaminacion.
Maestria en Ciencias Biologicas
Universidad Simon Bolivar
Tel: +58.212.9063415
Fax: +58.212.9063416