June 02, 2009 —
New research by UBC zoologists indicates that elevated water
temperatures and heightened concentrations of carbon dioxide can
dramatically increase the growth rate of a keystone species of sea star.
study is one of the first to look at the impact of ocean acidification
on marine invertebrates that don’t have a large calcified skeleton or
external shell, and challenges current assumptions about the potential
impact of climate change on marine species.
The findings were published online this week in the Proceedings of the National Academy of Sciences.
the lab, UBC researchers led by Rebecca Gooding manipulated water
temperatures and CO2 levels in sea water tanks containing juvenile
Purple Ochre Sea Stars (Pisaster ochraceus), a species found along much
of North America’s Pacific Coast.
An increase in temperature of
just three degrees and doubling of CO2 concentrations enabled the sea
stars to grow almost twice as fast as they normally would over a period
of ten weeks.
"This means the sea stars could potentially reach
adulthood in about half the time it would typically take-and consume
more mussels, their main diet, at much higher rates," says Gooding, a
PhD student in the Department of Zoology working under the supervision
of UBC Assistant Professor Christopher Harley.
At the end of the
period, sea stars reared in warmer, more acidic waters weighed 17
grams, compared to control sea stars that weighed an average of only 11
grams. In contrast, existing studies suggest that an increase in
temperature and CO2 levels hinder growth in most species studied so
far-usually more calcified species.
"This complicates current
assumptions. It looks like increased CO2 may not have negative effects
on all marine invertebrates, suggesting that predicting the impact of
climate change should consider how different organisms respond to
changing climatic variables."
The Purple Ochre Sea Star is a
cold-water species of sea star that can be found anywhere from Alaska
to Baja California. It is most commonly found in the North Eastern
Pacific. They can actually range in color from purple to orange to
brown and have five rays that can range in length from 10 to 25cm.
are considered a keystone species-a species that exerts a
disproportionate effect on their ecosystem by preying on other animals.
Source : The University of British Columbia