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Affect of Global Warming on Climate Change and
Phytoplankton
LiveScience Staff Writer Sara Goudarzi
- Dec 6, 2006
Satellite data revealed for the first
time that global warming could devastate
key
marine life,
scientists announced today. The
decade-long analysis showed that as the
surface water of the oceans warmed up,
phytoplankton
biomass declined.
Tiny marine plants, called
phytoplankton, impact the network of
organisms that directly or indirectly
depend on them for food. Changes in
ocean color—a measure of phytoplankton
mass—detected from space allowed
researchers to calculate their
photosynthetic rates and correlate these
changes to the climate.
As rising air temperatures heat up the
ocean’s surface, this water becomes less
dense and separates from the cold dense
layer below, which is full of nutrients.
Since phytoplankton need light for photosynthesis,
these floating plants are restricted to
the surface layer—now separated from
nutrients needed for growth.
When phytoplankton is abundant, the
color of the water shifts from blue to
green. These marine plants remove carbon
dioxide and convert it to organic
carbon, accounting for almost half of
the Earth’s photosynthesis. During periods of cooler temperatures,
there is a flowering of these marine
plants. Such was the case in late 1999
when the oceans were recovering from a
strong El Nino and the globe was
cooling.
But between 2000 and the present,
researchers found that as the oceans
warmed and became more stratified,
phytoplankton productivity declined by
190 million tons of carbon each year. “This clearly showed that overall ocean
productivity decreases when the climate
warms,” said lead author Michael Behrenfeld of Oregon State University.
Unlike terrestrial plants that can stick
around for hundreds of years, these tiny
greens have quick turnover rates. Every
two to six days, predators munch down
the entire global phytoplankton mass.
“This very fast turnover, along with the
fact that phytoplankton are limited to
just a thin veneer of the ocean surface
where there is enough sunlight to
sustain photosynthesis, makes them very
responsive to changes in climate,” Behrenfeld said. “This was why we could relate
productivity changes to climate
variability in only a 10-year record.
Such connections would be much harder to
detect from space for terrestrial plant
biomass.”
The problem could create a vicious
cycle. As the carbon dioxide levels rise,
phytoplankton production is reduced.
This means that there will be less ocean
plants to uptake this greenhouse gas,
which worsens the overall problem, Behrenfeld said. The study is detailed in the Dec. 7
issue of the journal Nature.
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