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December
19, 2010
Koh Tao’s Reefs – Recovery and
Associated Dangers
2010 has been a particularly
challenging year for the corals of Koh Tao with enormous thermal
stress being experienced on the island through the middle parts
of the year. Widespread coral bleaching resulted in mortality to
many acropora (branching) species of coral and some other species
of coral experienced differing levels of damage and death.
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| Branching
coral at White Rock with the beginings
of what looks like coral disease on its upper surface |
A
close up of the affected area! |
Now December, with water
temperatures more akin to what we would expect at this time of year,
the corals that survived the barrage are on the whole exhibiting
strong, vibrant, healthy colours and going from strength to strength.
There have been additional stressors including heavy sediment loads
from ferocious monsoon rains, the likes of which haven’t been
experienced on Koh Tao for a couple of years.
A new threat presenting itself at the moment is coral disease, where
pathogens prey on weak and fragile corals to attack. We are seeing
an increase in the incidence of diseases across the island but there
are only just starting to come out.
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| The
same branching coral (pictured above) a
week later showing the spread of the disease. |
A
close up of the affected area! |
Another pressing problem
is the damage being inflicted by the corallivorous snail, druppella
cornus which preys on the coral polyps. These have been widespread
for years on Koh Tao and have always preferred the faster growing
species of corals, like branching corals.
The problem is that many
of these corals have died so the druppella snails are aggregating
to the remaining live branching corals putting them at risk. In
addition many snails are beginning to prey on slower, previously
non-target species of corals seriously threatening the continued
health of much of the reef on Koh Tao.
We have conducted many snail collection dives trying to reduce the
number of isolated corals being eaten. We are only now beginning
to try and track the incidences of disease also. This is a more
challenging affair being a very new area of scientific study, very
little is known about coral disease and even less about what we
can do.
We will continue to track changes to the ecosystem and endeavour
to protect the reefs in the New Year. If you can offer your time
and dive experience please join us.
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