Optical Complexity of Coastal and Offshore Oceanic Waters: Implications for Shipboard, Airborne and Satellite Retrievals
Alexander
M
Chekalyuk, LDEO of Columbia University, chekaluk@ldeo.columbia.edu
(Presenting)
An extensive series of hyperspectral measurements of laser-stimulated emission (LSE) with multiple excitation wavelengths was conducted in the Middle Atlantic and Southern California Bights, California Current, Chesapeake, Delaware and Monterey Bay in 2005-2008. The data revealed significant optical complexity and variability of the LSE signatures in both coastal and offshore waters. The spectral deconvolution (SDC) analysis, which involves 15 spectral components, was developed to assess the key fluorescence constituents, including chlorophyll-a (Chl-a), phycobiliproteins (PBPs) and chromophoric dissolved organic matter (CDOM). It provides for discriminating 3 spectral types of phycoerythrin and assaying spectral variability in Chl-a fluorescence associated with photo-physiological and structural changes in phytoplankton populations. Potential for in vivo discrimination between cryptophytes and cyanobacteria, and assessment of their abundance in the mixed algal populations was demonstrated. The blue spectral shift in Chl-a fluorescence may allow detection and assessment of dinoflagellates in the phytoplankton communities. Three spectral bands peaking at 625, 644 and 662 nm detected in the field may be interpreted as fluorescence from partially dysfunctional photosynthetic apparatus of phytoplankton. The measurements suggest necessity (i) of hyperspectral LSE measurements and SDC analysis in various settings, including in situ, shipboard and airborne instruments, and (ii) of spectral correction of variable fluorescence measurements used for phytoplankton photo-physiological assessments. The use of the advanced laser fluorescence (ALF) measurements onboard airplanes and fast-moving vessels for improved calibration/validation of the satellite retrievals in coastal waters is discussed. The field observations that show potential for assessment of the PBP pigments from ocean color measurements are presented.
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