Satellite Maps of Phytoplankton Health
| The MODIS sensor on NASA’s Aqua satellite is demonstrating its capacity to detect phytoplankton chlorophyll fluorescence for globally monitoring climate-phytoplankton physiology interactions.
Phytoplankton Chl a fluorescence is a remotely retrievable property registering a variety of physiological characteristics with a long history of research and application, but satellite observations have been limited to date and mainly focused on near-shore areas and harmful algal blooms. In an article in the open access journal Biogeosciences, Behrenfeld et al. (2009) demonstrate the global patterns of Chl a fluorescence quantum yields, with generally high values found in Fe-low waters and low fluorescence where nutrient or other factors control growth. |
 Global map of phytoplankton fruorescence quantum yield (nonphotochemical quenching-normalised) for spring 2004 (March–May). Except for high latitudes, high Chl a fluorescence values from satellites (red) correlate with Fe-stressed zones, and low (blue) with nuttrient-stress zones. |
| "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." (NASA Press Release).
The study demonstrates a surprising seasonal phytoplankton stress from iron deficiency in the Indian Ocean, and highlight the short-timescales potential of the satellite sensor to monitor phytoplankton response to iron input via dust storms, as well as the potential of the global fluorescence dataset as a validation method for model predicted iron- and nutrient-stressed waters. Although the authors acknowledge limitations of the technique at high latitudes, where light plays an additional important stressor-role, the new data set is an important step forward toward global phytoplankton physiology monitoring under increased climate and anthropogenic stress, as well as offering a potential independent data set for evaluating satellite Chl a retrieval algorithms. Review for MEECE Research Highlights by Ivo Grigorov, IUEM, France. REFERENCE: M. J. Behrenfeld, T. K. Westberry, E. S. Boss, R. T. O'Malley, D. A. Siegel, J. D. Wiggert, B. A. Franz, C. R. McClain, G. C. Feldman, S. C. Doney, J. K. Moore, G. Dall'Olmo, A. J. Milligan, I. Lima, and N. Mahowald, 2009. Satellite-detected fluorescence reveals global physiology of ocean phytoplankton, Biogeosciences, 6, 779-794. DATA ACCESS and instructions: http://oceancolor.gsfc.nasa.gov/cgi/file_search.cgi |
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