Looks like we may lose more of the world's corals than most scientists
currently predict, if the ocean continues to warm:

NewScientist.com news service:
http://www.newscientist.com/article/dn10068-most-corals-unable-to-adapt-to-warming-oceans.html

# Roxanne Khamsi
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* Tamar Goulet, University of Mississippi
* Marine Ecology Progress Series

Three-quarters of the world’s coral reefs may lack the ability to cope
with climate change, despite previous optimistic predictions, according
to a new review of coral research.

Earlier studies had demonstrated that some corals are able adapt to
warmer water temperatures by forming new, additional symbiotic
relationships with algae. But a new analysis of more than 400 coral
species suggests that only one-quarter of them would be able to adapt in
this way.

These latest findings add to already bleak predictions for the world’s
coral reefs, which are also threatened by coastal pollution and
acidifying oceans. Stressors such as these cause coral to lose the algae
that keep it alive by supplying it with nutrients. Even a 1 degree rise
in temperature can cause the death of this fragile animal. Some experts
have predicted that Australia’s Great Barrier Reef will lose 95% of its
living coral by 2050.

However, two studies published in 2004 offered hope that some corals had
coped with changing water temperatures by hosting new types of algae.
For example, the corals along the Panama coast that were able to switch
from one type of Symbiodinium algae, known as clade C, to another one
called clade D.

These corals survived the particularly devastating 1997-1998 El Niño
event – a recurring climate occurrence that causes elevated sea
temperatures of up to 5°C on the longitude line that crosses Peru and
Ecuador (see Corals adapt to cope with global warming).
One at a time

Tamar Goulet at the University of Mississippi in the US carried out a
review of these two research papers and 41 others to try to understand
what proportion of all coral species might possess an ability to switch
algae.

She found the only corals documented to be able make this swap are those
that can host multiple algae. And those that can host only one clade, or
type, of algae at a time have no such switching ability.

Only 23% of the 442 coral species included in Goulet's research review
were able to host more than one clade of algae. As a result, she
suggests that less than one-quarter of coral species may have the
ability to adapt to climate change by swapping symbiotic algae. Without
adaptation, coral becomes bleached and dies.

However, Goulet says she does not know the division of species among the
world’s coral reefs: it is possible that adaptable species of coral are
more prevalent. The studies included in Goulet’s review only covered a
small fraction of the 93,000 coral species known to exist.

Journal reference: Marine Ecology Progress Series (vol 321, p 1, 2006)

-Ross Mayhew.

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