Bleaching & dissolved oxygen

Simon Wilson 106422.2221 at
Mon May 21 09:12:04 EDT 2001

Dear Peter

Corals in Oman also experience low oxygen concentrations periodically, not
caused by respiration at night but because of upwelling of water that
contains very little oxygen.  So far oxygen concentrations can only be
inferred from open water oceanographic measurements, but I would expect
values of less than 0.2mg/l at times.  I saw the effect on the benthos of a
strong upwelling in the Gulf of Oman last year that killed several hundred
tons of fish.  Mortality to invertebrates in reef areas was also high,
particularly for worms, sipunculids, gastropods and echinoderms. Hard
corals were more resiliant than soft corals, but they were also killed. The
tissue of hard coral became necrotic and then sloughed off revealing white
skeleton underneath, but I didn't see any signs of bleaching then or on
subsequent days.

Any references on the tolerance of coral to low oxygen concentrations would
be welcome.

All the best

Simon Wilson
PO Box 2531
CPO 111
Sultanate of OMAN

Tel & Fax:              00 968 736260
Mobile:                 00 968 9358053
E-mail:                 106422.2221 at

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