Research Papers

High spatial resolution spectrometry of rafting macroalgae (Sargassum)

[+] Author Affiliations
Karl H. Szekielda

NRL/ASEE Summer Senior Faculty Fellow, Washington, D.C. 20036

George O. Marmorino, Jeffrey H. Bowles, David Gillis

Naval Research Laboratory, Remote Sensing Division, 4555 Overlook Avenue, S.W., Washington, D.C. 20375

J. Appl. Remote Sens. 4(1), 043529 (April 28, 2010). doi:10.1117/1.3431044
History: Received October 5, 2009; Revised April 13, 2010; Accepted April 19, 2010; April 28, 2010
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Abstract

Data with 0.4-m spatial resolution acquired ~2 km off the southeast Florida coast using the airborne Portable Hyperspectral Imager for Low-Light Spectroscopy (PHILLS) have been analyzed with the objective of identifying drifting surface macroalgae (Sargassum) through its spectral signature in at-sensor radiance. The observed spectral features of Sargassum include a peak at a wavelength of ~0.570 μm and a photosynthetic 'red edge' between 0.673 and 0.699 μm. Sargassum also exhibits high radiance in the reflected near-infrared but is impacted by the atmospheric absorption bands of water vapor at 0.720 μm and oxygen at 0.756 μm. The spectral signature is clearest and largest in amplitude where the Sargassum occurs as small surface aggregations, or rafts, which tend to lie at the downwind ends of narrow Sargassum windrows. The quantity of floating Sargassum was estimated within a single pixel by linearly mixing a spectrum of Sargassum-free water with varying percentages of a spectrum from a pixel assumed completely filled with floating plants. For our study site about 2.3% of the ocean area is classified as having some Sargassum coverage, with pixels completely filled with Sargassum being rare (only 0.2% of the classified Sargassum pixels) and pixels with the least-resolvable amount of Sargassum (~10% filled) being the most common.

© 2010 Society of Photo-Optical Instrumentation Engineers

Topics

Spectroscopy

Citation

Karl H. Szekielda ; George O. Marmorino ; Jeffrey H. Bowles and David Gillis
"High spatial resolution spectrometry of rafting macroalgae (Sargassum)", J. Appl. Remote Sens. 4(1), 043529 (April 28, 2010). ; http://dx.doi.org/10.1117/1.3431044


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