[Coral-List] Tobago Bleaching update

[Jahson B]

Dear listers

As a follow up to my pervious post on "Coral bleaching and an unknown sponge
disease in Tobago", I returned to a monitoring site, surveyed only 10 dys
earlier, and I to my dismay, within the 20-40ft depth area there is mass
mortality of the Giant Barrel Sponges (Xestospongia muta).  Some of the
other songes are also looking a bit poorly, but not to the extent of
mortality.  Samples have been retrieved for analysis both heathy and
unhealthy looking X. muta.  That said, even heathy looking sponges were
snapping off at their bases.  There is also wide spread bleaching,
especially at the 23-35ft depth at Speyside, affecting most species
(Montastrea faviolata, Siderastrea sidera, S. radians, all Diplorias, M.
anularis, Millipora, octocorals etc). Speyside's reefs are generally sponge
dominated, but the main reef building coral species are Montastrea
faveolata, Siderastrea sidera, Diploria spp. and Madracis mirabilis.  At
deeper depths, up to 60ft moderate bleaching was observed, and only of
particular species (Meandrina meandrities and Siderastrea sidera).  The
water temperature at this depth was quite warm, with temperature loggers
recording on the reefs at 30ft showing temperatures up to 31 deg C.
 Interestingly some resiliency studies/models indicate that the longer lived
and slower growing species, such as boulder corals (Montastreas and
Siderastrea) are more resilient that branching species (Porities and
Madracis), however very very little bleaching of M. mirabilis was observed.
 M. mirabilis can be found in extensive spreads in Speyside with octocorals,
sponges, boulder and brain corals inter-dispersed.

Thus far the north eastern side of the island is the only location I've been
able to follow up on, but I have received reports of increased bleaching
along the Caribbean coast and south west of the island.

Jahson Alemu I
Coral Reef Ecologist


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