Estimated
surface ocean
pH in 1751
Surface
ocean pH
in 2004
Forecast
surface ocean
pH in 2100
Be more afraid,
young clownfish
In acidifying oceans, fish are
oblivious to alarming sounds
By Susan Milius
Greenhouse gases dissolving in the
world’s oceans may disrupt young
fishes’ natural reluctance to swim
toward scary noises.
When raised in water mimicking the
predicted acidifying chemistry of future
oceans, juvenile clownfish appeared perfectly willing to swim toward a speaker
broadcasting the recorded daytime
sounds of a reef teeming with predators,
says fish ecologist Steve Simpson of the
University of Bristol in England. “When
you’re a centimeter long as a fish, anything is a predator,” he says.
Juvenile orange clownfish (Amphi-
prion percula) looking for a home on
the reef normally spend minimal time
near such noises, Simpson explains. Yet
youngsters raised in water with condi-
tions predicted for midcentury oceans
spent at least half their time in the
alarming-noise end of an aquarium,
Simpson and his colleagues report online
June 1 in Biology Letters.
Corals that stay cool beat the heat
Species that overreact to loss of algae are more likely to die
By Tina Hesman Saey
Some corals seem to have a suicide pact
with the symbiotic algae living inside
them. But others are able to survive the
demise of their photosynthetic friends,
and now scientists think a suicide protein may explain the difference between
the two groups.
When waters warm, some corals over-
react to distress signals sent by resident
algae, researchers report online June 2
in the Proceedings of the National
Academy of Sciences. The overreactors
ramp up production of an executioner
protein called caspase and eventually
commit cellular suicide. Corals that are
able to survive warming start out with
high levels of caspase but then quickly
decrease the amount of the protein, the
researchers found.
Dan Tchernov of the University of Haifa
in Israel found. In contrast, another Red
Sea coral called Stylophora pistillata had
a meltdown and died after only a week in
the heat. Levels of caspase protein made
by the dying coral shot up to six times
normal levels, while levels of the protein
dropped in the heat-resistant coral.
Using two other wilting coral species,
the researchers found that adding a chemical that inhibits caspase activity could
stop the corals from committing suicide.
“Potentially, a single gene might
control the fate of a coral,” Falkowski
says. The coral’s survival depends upon
whether its cells initiate a self-destruct
program in response to its algae’s stress
signals. Species that can stand the heat
will probably be those that populate coral
reefs in the future. “We’ll certainly lose
the rest in the short term,” Falkowski
says, “and lose them in abundance.”
MATTHEW WITTENRICH
www.sciencenews.org
