Stresses on Global Phytoplankton

Researchers have conducted the first global analysis of
the health and productivity of ocean plants using a unique signal
detected by NASA's Aqua satellite.




Ocean scientists can now remotely measure the amount of fluorescent
red light emitted by phytoplankton and assess how efficiently these
microscopic plants turn sunlight and nutrients into food through
photosynthesis. Researchers also can study how changes in the global
environment alter these processes at the center of the ocean food
web.

Single-celled phytoplankton fuel nearly all ocean ecosystems, serving
as the most basic food source for marine animals. Phytoplankton
account for half of all photosynthetic activity on Earth and play a
key role in the balance of carbon dioxide in the atmosphere. The
health of these marine plants affects the amount of carbon dioxide
the ocean can absorb from the atmosphere and how the ocean responds
to a changing climate.

"This is the first direct measurement of the health of the
phytoplankton in the ocean," said Michael Behrenfeld, a biologist who
specializes in marine plants at Oregon State University. "We have an
important new tool for observing changes in phytoplankton every week,
all over the planet."

All plants absorb energy from the sun, typically more than they can
consume through photosynthesis. A small fraction of this extra energy
is re-emitted as fluorescent light in red wavelengths.

Using the Moderate Resolution Imaging Spectroradiometer (MODIS) on
NASA's Aqua satellite, scientists have now observed "red-light
fluorescence" over the open ocean. MODIS is the first instrument to
observe this signal on a global scale.

"The amount of fluorescent light emitted is not constant; it changes
with the health of the plant life in the ocean," said Behrenfeld.

Scientists previously used satellite sensors to track the amount of
plant life in the ocean by measuring the amount and distribution of
chlorophyll.

"Chlorophyll gives us a picture of how much phytoplankton is present,"
said co-author Scott Doney, a marine chemist from the Woods Hole
Oceanographic Institution in Woods Hole, Mass. "Fluorescence provides
insight into how well they are functioning in the ecosystem."

With this new measurement, the scientists discovered large areas of
the Indian Ocean where phytoplankton were under stress from iron
deficiency. They were surprised to see large portions of the ocean
"light up" seasonally as phytoplankton responded to a lack of iron in
their diet. The amount of fluorescence increases when phytoplankton
have too little iron, a nutrient in seawater. Iron reaches the sea
surface on winds blowing dust from deserts and other arid areas, and
from upwelling currents.

The research team detected new regions of the ocean affected by iron
deposition and depletion. In the fall and winter and especially the
summer, significant southwesterly winds over the Indian Ocean stir up
ocean currents and bring more nutrients up from the depths for the
phytoplankton to feed on. At the same time, the amount of iron-rich
dust delivered by winds is reduced.

Climate change could mean stronger winds pick up more dust and blow it
to the sea, or less intense winds leave waters dust-free. Some
regions will become drier and others wetter, changing the regions
where dusty soils accumulate and get swept up into the air.
Phytoplankton will reflect and react to these global changes.

"On time-scales of weeks to months, we can use this data to track
plankton responses to iron inputs from dust storms and the transport
of iron-rich water from islands and continents," Doney said. "Over
years to decades, we also can detect long-term trends in climate
change and other human perturbations to the ocean."

These findings appeared in the May edition of the journal
Biogeosciences.

Category:

Science & Technology

Tags:

• Stress
• Global
• Phytoplankton

[2bsirius]

Really interesting, as are most of your postings...even when they're scary -- as this one is.

[BrunoTheQuestionable]

Thanks 2bsirius. I don't really see this as scary. Our understanding of a small part of a very complicated system has changed. However, it does mean that there are more opportunities for iron seeding of the oceans than we thought.

[donnie2164]

very cool even though it seems a little incomplete in data..thank yo . I wonder can we use this satelite to caculate the damedge from the golf?

[sidewaysjsideways]

i am an adamu not of this earth but a hybrid like everyone else part Anunnaki and part Neanderthal

[2bsirius]

Great optimism

[kurtilein3]

the plant, when it absorbs a photon for photosynthesis and somehow the reaction doesnt work properly, so that the energy gets lost somewhere along the way instead of being used productively by the plant, you might get a photon leaving the plant.

so those emissions are a very direct sign of plants in trouble, when the emitted photons directly result from failed photosynthesis reactions.

[Aiden057]

Is it the plants that are giving off the light, or is it bacteria that are fluorescing due to quorum sensing?

[timegrinder]

fascinating as always, thanks bruno.