[Coral-List] Coral Bleaching in Thailand

Bill Allison allison.billiam at gmail.com
Wed May 19 08:35:10 EDT 2010

Hello James,
The situation is paralleled in Maldives including the contrast to 1998, but
to date temperatures have not been so high, there has there been as much
bleaching as you describe, and unsettled weather gives reason for optimism,
but I watch with concern.


On Tue, May 18, 2010 at 11:25 PM, james true <jaydeetee1 at gmail.com> wrote:

> Dear Listers
> Over the past month, bleaching of hard and soft corals has been observed on
> both sides of the Thai peninsula (i.e., Andaman Sea and Gulf of Thailand).
> The bleaching is the worst that has been reported since the 1998 bleaching,
> but differs significantly in that, during the 1998 event, the Andaman Sea
> reefs were essentially unaffected. The bleaching corresponds to an
> unusually protracted period of calm weather, significantly elevated sea
> surface temperatures around offshore islands and a slight tardiness in the
> onset of normal monsoon rainfall and wind conditions.  Bleaching appears to
> be less severe in those localities where rainfall has occurred.
> On the Andaman side, extensive bleaching has been reported at offshore
> locations in the northern Surin Islands (which are the southernmost of the
> Mergui chain extending into Myanmar) and in the Tarutao/ Adung-Rawi complex
> in the far south (adjacent to northwest Sumatra).  Bleaching has not been
> reported in the Similan Islands, which are subject to seasonal upwelling
> from the current SW monsoon.  The bleaching in the Andaman reefs includes
> all major families, although faviids, agariciids and pocilloporids appear
> to
> be strongly affected; acroporids, poritids and mussids appear slightly less
> vulnerable to bleaching under current conditions. Acroporas appear not to
> be
> the most severely affected group, except for table and corymbose species;
> branching Acroporas are frequently bleached only on their upper surface.
> On the Gulf side, bleaching has been reported at Koh Tao (offshore), and at
> inshore islands in Chumphon and Prachuap provinces.  Shallow reefs around
> Koh Tao are 40-60% bleached; affected groups include pocilloporids,
> agariciids, poritids and other symbiotic orgainsms such as giant clams.
> Acroporas are affected as for the Andaman description.  Correspondents on
> Koh Tao also report a significant surge in diseases affecting corals,
> especially a "patch lesion" affecting Porites.  Bleaching in Prachuap
> varies
> strongly with location: shallow reefs (such as Koh Singha) are 60-70%
> bleached, mostly in shallow (<2m) locations; slightly deeper reefs
> (4-6m) around Koh Talu are only ~10% bleached - mostly amongst the
> agariciids and fungiids.
> Bleaching in the east coast reefs of the Gulf of Thailand (towards
> Cambodia)
> is variable, but appear to average ~40% bleached.  Affected corals in
> Rayong
> Province are as described for Prachuap.  Reefs in Chantaburi Province
> (further east from Rayong) are reported to also exhibit extensive bleaching
> in soft corals, with 100% bleaching of Sarcophyton reported.
> No bleaching has been reported for the Inner Gulf region (Chonburi
> Province).
> Data loggers record that water temperatures at Koh Tao were elevated for
> most of April, peaking at ~34 degrees C in early May.  Some minor bleaching
> of the upper surfaces of branching Acropora was noticed during the faviid
> spawning event in early April, when water temperatures were ~32 degrees C.
> No significant rainfall has occurred there this calendar year, and
> conditions have been generally very calm.  Sea surface temperatures did not
> exhibit the usual "winter" low this year, and seem to have peaked much
> earlier than "normal" years ... by way of contrast, the 1998 SST peak did
> not occur until the end of May at Koh Tao.  Water temperatures recorded by
> loggers around Koh Mun (Rayong province) were likewise elevated, with
> temperatures above 33 degrees C for a large proportion of April and early
> May.
> - James
> --
> Dr James True
> Center for Biodiversity in Peninsular Thailand
> Faculty of Science, Prince of Songkla University
> Hat Yai, Thailand
> Tel: (+66) 2235 3062
> Mob: (+66) 89 002 4490
> Email: jaydeetee1 at gmail.com
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"reality leaves a lot to the imagination..."  John Lennon

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