THE
COLORS OF LIFE
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numerous images and animations contained on this page, which
may result in longer downloads. All SeaWiFS visualization
courtesy: NASA/GSFC and ORBIMAGE
INTRODUCTION:
Everything
about life on Earth depends on life in the ocean. After all,
this is a blue planet, with about 70 percent of the total
surface awash with one of the most common molecular compounds
known: water.
The oceans regulate
the planet’s biological well being. But water alone is not
enough. Life in its most common forms demands a ready supply
of a particular element if it’s to thrive: carbon.
It’s the same stuff
that composes lowly coal, and it’s the core of proud tree
trunks. Carbon is the root of all life on Earth, and as its
complex dance carries it through the biosphere, the Earth’s
state of health responds.
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THE
COLORS OF LIFE, THE COLORS OF THE WORLD
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COLORFUL
SHADOWS: INFERRING CARBON’S CYCLE
By
monitoring the color of reflected light via satellite, scientists
can determine how successfully plant life is photosynthesizing.
A measurement of photosynthesis is essentially a measurement
of successful growth, and growth means successful use of ambient
carbon.
Until
now, scientists have only had a continuous record of photosynthesis
on land. But following three years of continual data collected
by the SeaWiFS instrument, NASA has gathered the first record
of photosynthetic productivity in the oceans. The process
begins with a measurement of surface chlorophyll concentration.
Chlorophyll
is the material that allows plant cells to convert sunlight
into energy, thus enabling them to grow. It’s a green substance,
and thus a good indicator of overall plant health: robust
forests and lush lawns and vibrant phytoplankton blooms
appear green. By measuring chlorophyll concentration, scientists
can determine the health and growth of plants in a given area.
By extension, healthy color signatures indicate the successful
use of carbon, the fundamental building block for life. In
other words, lots of green indicates lots of chlorophyll;
lots of chlorophyll implies healthy photosynthesis; strong
photosynthesis indicates growth, and growth indicates successful
use of carbon.
Over the past
twenty years, researchers have amassed a repository of chlorophyll
concentration data about the land. That measurement is called
NDVI, for the Normalized Difference Vegetation Index. But
chlorophyll concentration measurements regarding the ocean
have remained elusive.
This
release from the SeaWiFS research team marks the first continuous
record of surface chlorophyll concentration in the ocean.
The power of these three years of collected data can be summed
up by a single word: continuity. By taking three years of
continuous data as a whole, experts have been able to map
trends and anomalies in the global circulation of carbon to
a degree of detail than has never been done before. It is
a baseline measurement to by which all future measurements
will be compared.
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WATER
PLANET: LIVING PLANET
NASA designed
SeaWiFS to study ocean processes. But the mission has surpassed
its initial design goals. By carefully calibrating the sensor,
experts have been able to use SeaWiFS data to monitor life
on land, too.
In addition to
the release of the first validated carbon cycle data, the
project has noticed an increase in plant productivity on land
in the past three years. This is interesting because supporting
research shows that there hasn’t been any atypically fast
growth on land in that time. Scientists conclude that the
increased productivity is tied to increased rainfall averages
connected to the most recent El Nino phenomena.
As we consider
a globe painted in the color-coded data gathered by SeaWiFS
over the last three years, it’s important to note the relative
oxygen production of plant life in the ocean versus on land.
While the ocean doesn’t put out as much oxygen per square
meter as vibrant rainforest, taken as a whole the ocean does
produce roughly the same amount as the Earth’s total land
surface. This is due to the vastly larger area of ocean on
the surface, essentially making up for the discrepancy in
square meter productivity.
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THINK
SMALL: PHYTOPLANKTON
AND THE CARBON CYCLE’S FOUNDATION
The
ocean is not simply empty space filled with water and the
occasional fish. It teems with life of myriad varieties, and
pulses like a heartbeat with the changing seasons. That rhythm
plays a fundamental role in regulating the health of all life
on Earth.
But while the familiar forms of stingrays and blue whales
and kelp beds and sea urchins are the most easily recognizable,
in terms of the biosphere, the action starts in a different
population.
It’s
called phytoplankton. They’re tiny, single celled plant organisms
that form the root of the oceanic food chain. Little more
than bits of greenish implications of life, immense and uncountable
clouds of these plants appear like floating carbon signatures
around the globe, offering evidence about the planet’s health
for those who can read the signs.
The
word "phytoplankton" comes from the Greek. Phyto-,
meaning "plant", and –plankton meaning "free
floating". The most common species of phytoplankton is
a tiny specimen called prochlorococcus. Each individual in
a colony of prochlorococcus measures less than one micron
across. In fact, it’s largely due to the extremely small size
of this humble life form that its existence wasn’t even known
until the middle of the 1980s. The same goes for a sibling
species of phytoplankton called synococcus. Although less
common than prochlorococcus and slightly larger, by itself
it composes one of the most populous photosynthetic life forms
on the Earth.
For
years, researchers have only been able to study phytoplankton
in discrete areas and synthesize a variety of suppositions
about how it interacts with the natural world. But a global
look at these humble plants has not been possible. Until
now.
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SPRING
BLOOM in the NORTH ATLANTIC
The annual bloom
of phytoplankton in the North Atlantic is one of the biggest
regular blooms in the world. As seen here, the area covered
by the bloom is larger than the territory covered by the Amazon
rainforest in South America. In the open waters of North Atlantic,
it’s believed that lots of carbon initially taken up by phytoplankton
ultimately settles to the ocean floor, as the region is not
densely populated by zooplankyton, the next logical rung on
the food chain. Although still inconclusive, studies of this
area suggest strong evidentiary clues as to the process of
carbon uptake and long duration carbon sequestration.
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WESTERN
CENTRAL AMERICA
Along the West
Coast of Central America we see extraordinary levels of phytoplankton
growth, due largely to cold water upwellings along the eastern
basin of the Pacific Ocean. This area rich in life supports
a healthy and vibrant diversity of species, each with unique
strategies for survival, but all ultimately dependent on the
first link in the food chain. In human terms this has direct
relevance to fishermen in the region, as the area is world
famous for its significant tuna stocks.
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EQUATORIAL
ATLANTIC
– RIVER OUTLETS SUPPORT LIFE
Deep ocean waters
are not the only sources of nutrients for phytoplankton. The
mouths of rivers often wash tons of nutrient rich water into
the sea, providing abundant resources for all sorts of life.
Much of the nutrients
that wash downstream are themselves functions of the carbon
cycle as played out on land. Decomposing plant and animal
matter that might have otherwise been sequestered on land
can find their way into rivers and streams, feeding into the
ocean.
South America
presents two excellent examples of river outlets where phytoplankton
tend to thrive. Along the northern part of the continent the
mouth of the Orinoco River opens into the Caribbean. Along
the Eastern side of South America, the mighty Amazon exits
its thousand mile journey. At the end of each, notice the
bright red tails waving against the largely blue-green background
of surrounding Atlantic ocean. That’s the signature of intense
photosynthesis happening—billions of phytoplankton making
their home in those currents, feeding off carbon saturated
foodstuffs and turning sunlight into energy for life.
Also captured
in this frame is a strong signal of phytoplankton growth coming
off the western coast of Africa.
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WESTERN
AFRICA
Along
the western coast of Africa, intense phytoplankton blooms
wave back and forth in Atlantic currents like fern fronds
in a breeze. These gigantic fields of phytoplankton are the
products of several factors, including coastal cold water
upwellings and nutrient rich outflows from central African
rivers. The middle parts of the African continent support
extraordinarily dense networks of life, and the natural runoff
from the region has a nourishing effect on life off shore.
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A
SPLASH OF COLOR IN THE PACIFIC
The
bloom associated with the 1997 to 1998 El Nino to La Nina
transition event splashed across the Pacific Ocean like pigment
thrown across empty canvas. Jetting from west to east, the
explosive, yet short lived growth spurt there coincided with
significant upwellings of cold water corresponding with the
onset of La Nina. During the powerful 1997 El Nino event,
SeaWiFS recorded little or no significant growth of phytoplankton
in the equatorial Pacific.
Although
this visualizations features an intense bloom in the Pacific,
it’s interesting to note that the El Nino/La Nina phenomena
as its cause also contributed to simultaneous decreases in
phytoplankton growth in the western Pacific and large increases
in growth just east of Argentina.
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