NASA satellite detects red glow to map global ocean plant health

May 29th, 2009 - 1:34 pm ICT by ANI  

Washington, May 29 (ANI): Scientists have conducted the first global analysis of the health and productivity of ocean plants using a unique red glow detected by NASA’s Aqua satellite.

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.

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 (CO2) 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,” he added.

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.

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

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.

“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,” said co-author Scott Doney, a marine chemist from the Woods Hole Oceanographic Institution in Woods Hole, Massachusetts.

“Over years to decades, we also can detect long-term trends in climate change and other human perturbations to the ocean,” he added. (ANI)

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