Fishes Prove To Be Big
Fans Of Corals
Hardy Red Sea Corals Forged By Hard Times
Using coral branches as
shelters and nests, the
Damselfish Dascyllus
marginatus is known to
live in symbiosis with the
coral Stylophora pistillata.
In return for shelter, the
activities of the fish indirectly
remove sediment from the
coral surfaces, but there is
a surprising and previously
unknown benefit to this
arrangement too.
Measuring oxygen levels
inside the branches of corals
kept in test tanks either
with or without fish, Nur
Garcia-Herrera at the Alfred-
Wegener Institute in Germany
and colleagues found that
photosynthesis rates were
higher during the day in tanks
containing fish. Indeed the
presence of fish increased
photosynthesis by an amazing22 per cent.
“This is the first evidence
of positive effects by a
coral-associated fish on coral
photosynthesis. Many corals
live in environments where
currents are low and the
concentration of pollutants
and ocean acidification
parameters are high,” said
Garcia-Herrer, “therefore,
through the ventilation, the
fish are helping the corals
to cope with such hard
conditions.”
The ventilation by the fish
could provide some relief
from the build-up of warm
water and excess oxygen
among the coral branches,
says Sebastian Ferse, Garcia-
Herrera’s colleague at the
Leibniz Centre for Tropical
Marine Research in Germany.
This may help to counteractthe bleaching risk associated
with global warming. “Another
important point is that fish
may spend less time among
the branches if their predators
are removed, for example if
reefs are overfished,” he said.
“In that case, the damselfish
may opt to spend moretime foraging outside the
coral. Overfishing may thus
have previously overlooked
negative side-effects on coral
physiology.”Journal reference: Journal of
Experimental Biology, DOI:
10.1242/jeb.Although global warming is
already causing devastation to
parts of the Great Barrier Reef
and many other coral reefs, the
unique evolutionary history of
corals in certain other parts of
the world means they might not
just survive, but even thrive late
into this century despite the
rising heat.
Using a new outdoor aquariaknown as the “Red Sea
simulator” at the Interuniversity
Institute for Marine Sciences in
Eilat, Israel, Thomas Krueger of
the Swiss Federal Institute of
Technology in Lausanne and
colleagues subjected the SPS
coral Stylophora pistillata, which
is common in the Northern Red
Sea, to conditions expected
from 2050 to 2100. The result...it grew even faster! “The
experimental temperatures
were quite extreme, yet the
corals survived,” explained
Terry Hughes of James Cook
University in Townsville,
Australia, who has been
documenting die-off in large
areas of the Great Barrier
Reef. Surprisingly, the coral
was also unaffected by thelevel of ocean acidification
expected in the second half of
this century, and there is the
suggestion that other coral
species in the northern Red
Sea may also prove highly
resilient. This perhaps results
from the isolation and then
reconnection of the Red Sea
during the last Ice age, the
latter part of which saw corals
recolonise harsh environments
from the South.
Although initially
encouraging, it must be said
that the study only involved
one coral species, and did not
look at reproductive success or
the effect on coral ecosystems
as a whole. Furthermore, the
Red Sea is just as sensitive to
pollution as those from other
areas.Journal reference: Royal Society
Open Science, DOI: 10.1098/
r sos .170 0 3
Image: J Clipperton06 http://www.ultramarinemagazine.co.uk
Image: J Clipperton