Climate Change Having Major Impacts on Oceans

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“Phytoplankton are of tremendous human importance because their
photosynthesis yields oxygen for us to breathe and they are the base
of the ocean food webs that support our global fisheries,” Behrenfeld
said

“Unfortunately,” he added, “it is at this very time when we need
satellites most that we are facing the end of NASA ocean biology
satellites because of budget cutbacks or new priorities. This is a
serious issue that needs to be addressed.”
——————————————

Oregon State University
Public release date: 17-Feb-2008

Contact: Jane Lubchenco
lubchenco@oregonstate.edu
541-740-1247

Climate change has major impact on oceans

BOSTON, Mass. – Climate change is rapidly transforming the world’s
oceans by increasing the temperature and acidity of seawater, and
altering atmospheric and oceanic circulation, reported a panel of
scientists this week at the American Association for the Advancement
of Science (AAAS) annual meeting in Boston.

“The vastness of our oceans may have engendered a sense of
complacency about potential impacts from global climate change,” said
Jane Lubchenco, the Wayne and Gladys Valley Chair of Marine Biology
at Oregon State University, who moderated the panel. “The world’s
oceans are undergoing profound physical, chemical and biological
changes whose impacts are just beginning to be felt.”

Panelist Gretchen Hofmann, a molecular physiologist at the University
of California, Santa Barbara, describes the situation as “multiple
jeopardy.”

“Ocean ecosystems are facing new stresses and new combinations of
stress,” Hofmann said. “The water is warmer, circulation patterns are
changing in unpredictable ways, and oceans are becoming acidic.”

Rising greenhouse gas emissions are warming the world’s oceans and
providing yet a new threat to coral reefs, which already are among
the most threatened of all marine ecosystems, the panelists say. Even
modest warming of a degree or two above normal maximum temperatures
can cause a breakdown in the relationship between corals and their
symbiotic algae, zooxanthellae, said Nancy Knowlton, a marine
biologist with the Smithsonian Institution.

Without zooxanthellae corals appear white, or “bleached,” and grow
more slowly. They also are more susceptible to disease and may not
reproduce. In 1998 there were worldwide mass bleaching events,
Knowlton pointed out, affecting 80 percent of the corals in the
Indian Ocean, 20 percent of which died. In 2005, severe bleaching
occurred over much of the Caribbean as a result of overly warm water
temperatures.

“We have already lost some 80 percent of the reef corals in the
Caribbean over the last three decades, and losses in the Pacific
Ocean also are widespread and severe,” Knowlton said. “Reefs are like
cities, with some parts growing and some parts being destroyed, and
only when net growth is positive can reefs persist. These reefs
already are under threat to overfishing and local pollution and
unless drastic action to reduce greenhouse gas emissions is taken
soon, these reefs will cease to exist as we know them.”

These same greenhouse gas emissions also are creating dramatic
buildup of atmospheric carbon dioxide, which is rapidly making the
world’s oceans more acidic, said panelist Scott Doney of the Woods
Hole Oceanographic Institution. Current CO2 levels of 380 parts per
million already are 30 percent higher than pre-industrial values and
many scientific models predict that those rates will triple by the
end of the century under “business as usual” scenarios.

While much of the scientific attention on ocean acidification has
looked at the impact of coral reefs, the potential danger to other
marine ecosystems is equally severe, Doney said.

“Ocean acidification harms plants and animals that form shells from
calcium carbonate,” he said. “Calcifying organisms include not just
corals, but many plankton, pteropods (marine snails), clams and
oysters, and lobsters. Many of these organisms provide critical food
sources or habitats for other organisms and the impact of
acidification on food webs and higher trophic levels is not well
understood.

“Newly emerging evidence suggests that larval and juvenile fish may
also be susceptible to changes in ocean pH levels,” Doney added.
“Ocean acidification is rapidly becoming a real problem.”

Michael Behrenfeld, an oceanographer from Oregon State University, is
studying relationships between climate and the global activity of
ocean plants called phytoplankton.

“Phytoplankton are of tremendous human importance because their
photosynthesis yields oxygen for us to breathe and they are the base
of the ocean food webs that support our global fisheries,” Behrenfeld
said. “Using NASA satellites, we can track changes in phytoplankton
on a global basis and what we find is that warming ocean temperatures
are linked to decreasing photosynthesis. Satellites are one of the
most important tools we have for understanding the link between
climate and ocean biology because they provide measurements of the
whole planet on a daily basis, which could never be accomplished by
ship.

“Unfortunately,” he added, “it is at this very time when we need
satellites most that we are facing the end of NASA ocean biology
satellites because of budget cutbacks or new priorities. This is a
serious issue that needs to be addressed.

“Instead of facing the end of these critical missions and becoming
blind to the changes occurring in our oceans,” Behrenfeld said, “we
should be building even better ones to see more clearly than we have
in the past, and to gauge the potential consequences of climate
change on ocean productivity.”

The panelists also called for greater investment in ocean observing
systems that would allow scientists to better measure changing in the
ocean ecosystem, including large-scale circulation and coastal
upwelling systems around the world. Klaus Keller of Penn State
University reported on the economic costs and benefits of effective
ocean observing systems to detect changes in the north Atlantic
Meridional Overturning Circulation.

Jack Barth, an oceanographer at Oregon State University, reported on
the hypoxia events that have plagued the Pacific Northwest coast
since 2000. These low-oxygen zones in the near-shore are
unprecedented over the last five decades of scientific observation
and likely linked to stronger, more persistent winds that are
expected to occur with global warming. The California Current System
provides a case study for similar changes in coastal upwelling zones
off South America, southern Africa and northern Africa, Barth said.

“One of the things we’ve observed is how wind patterns have changed
and greatly affected upwelling,” Barth said. “Two decades ago, the
winds would last for three or four days, and then subside. Now they
persist for 20 to 40 days before settling down. This creates
significant impacts on upwelling and biological productivity, but
these impacts can swing wildly from one extreme to another and have
been difficult to predict.”

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The AAAS symposium was organized by the Partnership for
Interdisciplinary Studies of Coastal Oceans, a multi-university
research effort headquartered at Oregon State University and funded
by the David and Lucile Packard Foundation, the Gordon and Betty
Moore Foundation, the National Science Foundation and other sources.

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