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Coral Cores Reveal
Caribbean Confl icts
J u n e 2 017 05Science & Conservation
Surprising new research led
by the Scripps Institution
of Oceanography at the
University of California San
Diego, and published in
the journal Ecography, has
suggested that a species of
reef fi sh may be impeding
the recovery of Diadema
antillarum, the Caribbean
long-spined sea urchin.
Since urchins produce large
numbers of eggs throughout
the year, scientists initially
expected that they would
rebound rapidly after suff ering
a massive die-off caused by amysterious disease outbreak
over three decades ago, so
their failure to do so is a big
question among coral reef
scientists.
Analysing fossilised urchin
spines in cores of reef
sediment layers from the past
3,000 years, and then applying
a modelling approach to
detect cause-and-eff ect
relationships in ecological
systems, lead author Katie L.
Cramer of the Smithsonian
Tropical Research Institute
and her colleagues were able
to ‘paint a picture’ of life onthe reef before it was altered
by the disease outbreak and
recent human activities.
Furthermore, they were able
to deduce that, as Acropora
cervicornis (staghorn coral),
increased in abundance, long-
spined urchin populations
decreased. In light of this
surprising fi nding, they
theorised that the aggressiveterritorial activities of Stegastes
planifrons (the Threespot
Damselfi sh), a competitor of
the long-spined urchin that
takes refuge in the coral, was
at work. “These damselfi sh
pick up urchins and move
them off the coral with
their mouths,” said Cramer.
“Damselfi sh populations
appear to have grown recently
as their predators have been
overfi shed, which is one
plausible explanation as
to why long-spined urchin
populations have failed to
r e cove r ”.
“This study sheds light on
the many surprising ways
that fi shing can alter reef
ecosystems,” said Richard D.
Norris, a paleooceanographer
in the Geosciences Research
Division at Scripps and a
co-author of the study. “Our
fi ndings suggest that these
eff ects should be considered
in the future management of
Caribbean reefs.”Journal reference: Ecography,
2 017; D O I : 10 .1111/e c o g. 0 2 513
A diadem sea urchin seen in the Bahamas (image: Greg Grimes, Wikimedia Commons)Stegastes planifronsPhoto by JT Williams