BUFFALO, N.Y. -- Hopes that coral reefs might be able to
survive, and recover from, bleaching caused by climate change may
have grown dimmer for certain coral species, according to new
research by University at Buffalo marine biologists published
online this week in PLoS One.
The research shows, for the first time, that while hard corals
can take up from the environment new stress-tolerant algae that
provide critical nutrients, the coral may not be able to sustain
the relationship with these algae over a long period, a process
known as symbiosis.
The findings may mean that certain types of coral will not be
able to adapt rapidly enough to survive global warming, says the
study's lead author, Mary Alice Coffroth, PhD, UB professor of
geological sciences in the College of Arts and Sciences.
"Our findings suggest that not all corals can maintain a
long-term symbiosis with these stress-tolerant strains of algae,"
"That's the problem," Coffroth continues, "if they can't take up
the stress-tolerant symbionts, or if they take them up but can't
maintain the symbiosis with them, as we found, then they likely
won't be able to adapt rapidly enough to survive global
The demise of coral reefs will deprive fish of food and shelter,
severely threatening reef fish populations and marine
Co-authors on the paper include Eleni L. Petrou, a recent UB
Honors College undergraduate who worked in Coffroth's lab, as well
as Daniel M. Poland, a recent PhD graduate, and Jennie C. Holmberg,
a former graduate student, both of whom worked in Coffroth's lab,
and Daniel A. Brazeau, research associate professor in UB's
Department of Pharmaceutical Sciences.
During the past two decades, Coffroth explains, coral reefs,
known as the rain forests of the sea for their incredible
biological diversity, have suffered bleaching events due to high
water temperatures and light levels that cause them to literally
"spit out" their algal symbionts, which provide their sustenance.
Severe bleaching can lead to coral death.
In recent years, though, it has been reported that some corals
appear to respond to rising sea temperatures by acquiring new
stress-tolerant symbionts from the environment, which could allow
them to survive the warmer oceans caused by climate change.
Coffroth says that the UB research shows that while the corals
they studied were able to acquire new stress-tolerant symbiont
strains from the water, they were unable to maintain that symbiosis
for very long.
After about five weeks, the proportion of new symbionts within
the coral had declined dramatically and after 14 weeks was no
longer detectable in the corals.
"While it's true that coral can be flexible in the kinds of
symbionts they take up, that will only work within limits," she
says. "It's possible that the new symbionts were either unable to
multiply in the host or to compete with the existing residual
populations of symbionts in the coral.
"Our findings suggest that if a coral doesn't naturally host
this kind of stress-tolerant symbiont, it cannot acquire it from
She noted that the outlook may be more promising for corals that
naturally harbor the stress-resistant symbionts. These symbionts
appear to be able to protect corals from sea temperatures that are
one-to-two degrees higher than normal; however, Coffroth cautions
that most estimates predict that by the year 2100, global warming
will cause sea temperatures to rise by as much as two-to
six-degrees above current temperatures.
The UB researchers studied Porites divaricata, a common
shallow-water scleractinian coral found throughout the
The coral samples were retrieved from a site within the Florida
Keys National Marine Sanctuary; in the laboratory, the scientists
induced bleaching by exposing the coral to incremental increases in
water temperatures until it reached 33 degrees C, about 91 degrees
The research was funded by the National Science Foundation and a
grant from the UB Honors College Research and Creative Activities
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