World's Oceans Get an Acid Bath: Increasing acidity in the world’s oceans could pose a greater threat to marine life than warming waters
VANCOUVER, British Columbia -
Among
the repercussions of global climate change, the effect of ocean
acidification on marine life is one of the least-understood variables.
The oceans have already absorbed about one-third of the 500 billion
tons of carbon dioxide that human activity has added to the atmosphere
since the industrial revolution.
Absorbing carbon dioxide reduces the pH
of seawater, indicating an increase in its acidity.
While more attention has been focused on the ecological fragility of
coral reefs, cold-water life in other regions -- from urchins and
sea-stars to tiny plankton-like copepods -- may be more at risk than
their warmer-water counterparts, according to information presented at
the American Association for the Advancement of Science annual meeting
in Vancouver.
Like many effects of climate change, the impacts of acidification can vary from place to place.
"Ocean warming-related issues that have economic punch will not be
evenly spread around the globe," said Gretchen Hofmann , a professor of
marine biology at the University of California, Santa Barbara. "They
will be local, focal, and intense."
The physical mechanisms are clear: because cold water tends to hold more
gas, the Arctic and Antarctic oceans already contain more carbon
dioxide than other areas. In a world with oceans even more acidic than
they are today, marine creatures that form shells or body structure from
calcium carbonate may struggle to create their structures. Losing those
species will negatively affect species that are higher up on the food
chain, like herring.
Already, some oyster hatcheries in the Pacific Northwest recently failed
to produce oysters because the water had become too acidic for the
larvae to form shells, Hofmann said.
Scientists are just beginning to predict what will happen in the future
with more acidic waters. Jason Hall-Spencer, of Plymouth University in
the U.K., studies life at sites where natural carbon dioxide bubbles
like a Jacuzzi from the ocean floor. He chooses places along the
carbon-rich sea floor vents that mimic the effects of high acidity in
the rest of the ocean’s future -- a time machine for looking at hundreds
of species in conditions that will exist 10 or 50 years down the road.
Hall-Spencer has studied volcanic vents in Italy, California and Papua
New Guinea. All of them show similar effects. "What we see are dramatic
shifts in ecosystems, with a tipping point predicted at end of this
century," he said. That tipping point would spell out a 30% drop in
biodiversity in everything from corals to fish, he added.
Hall-Spencer said that some organisms strain attempt to keep up with
changing conditions. "It's like us panting for oxygen at high altitude -
they're struggling," he said.
Hall-Spencer called the combination of warming and acidification "a
deadly noxious cocktail." He said that worst-case scenarios predict
that acidity will increase another 150 percent by 2050 -- and warming
and acidification are a double-whammy.
Other researchers are studying the ability of microorganisms to adjust
to new environmental conditions. Sinead Collins, a research fellow at
the University of Edinburgh in the U.K., studies microevolution in
phytoplankton -- the tiny ocean floaters who are responsible for half
the photosynthesis on Earth.
Collins takes micro-algae and subjects them to a high-carbon-dioxide
environment for hundreds of generations, watching how they evolve. She
has seen them change.
"Some of them began to photosynthesize really quickly, but just spit
carbon back out. Current algae are much more efficient at capturing
carbon dioxide," said Collins.
Collins has found that the organisms are able to adapt, but their rate
of change slows as the speed of environmental change speeds up.
"If you take an antibiotic and introduce it slowly, antibiotic
resistance happens readily. But if you take it at a high dose, suddenly,
resistance takes longer to evolve," explained Collins.
The studies are not meant to be an oracle to predict the exact future.
"Experimental evolution is not a crystal ball. It can’t replicate the
glorious real world, but it lets you know the rules the real world plays
by," said Collins.
Katharine Gammon is a freelance science writer based in Santa
Monica, Calif., and writes for a wide range of magazines covering
technology, society, and animal science
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