bleaching-more food for thought

[Precht, Bill]

Happy New Years...

In a recent posting... Judy Lang wrote the following:

	"The confusion between freshly-exposed white skeletons and bleached
corals
	(particularly acute when observers have poor eyesight and lack
corrective,
	underwater lenses).
	---My experience at dive shops in the wider Caribbean is that the
mass
	bleaching events, especially during 1998, were such large-scale
phenomena
	that many amateurs have learned to tell the difference between
bleached
	(live but colourless soft tissues, through which the white of the
underlying
	skeleton is clearly visible) and parts of corals that are very
recently dead
	(for any reason), particularly the divemasters who watched some
bleached
	corals die whilst others gradually regained their symbionts.

	Divers in general tend not to understand that coral polyps are also
killed
	by predators, competitors and parasites, in addition to severe
bleaching and	
	biotic diseases."

Although the 1998 bleaching was dramatic... in reading this passage I am
reminded of going down to Belize in 1992 (a non-bleaching year in Belize).
I ran into a prominent reef scientist who knew of my work on the rhomboid
shoals there... he told me that I needed to take a look at the dramatic
bleaching event that seemed to be Acropora cervicornis specific on these
reefs.  Well these corals were not "bleached" in the scientific context, but
had recently died due to white-band disease.  The moral to this story is
even trained observers miss or confuse even the most obvious
signals...relying on observations by non-scientists only confounds and often
hinders our understanding of even the most dramatic events.  The Caribbean
wide impact of white-band disease and the demise of the acroporids being the
most obvious case in point...

Better observations... not just more of them is what we need if we are to
effectively manage these ecosystems into the next millennium.

Cheers,

Bill

William F. Precht
EcoSciences Program Manager
PBS&J
Miami