Rosado Torres, Marcos A.

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    Evaluation and development of bio-optical algorithms for chlorophyll retrieval in western Puerto Rico
    (2008) Rosado Torres, Marcos A.; Armstrong, Roy A.; College of Arts and Sciences - Sciences; García Sais, Jorge R.; Gilbes Santaella, Fernando; Ramírez Beltrán, Nazario D.; Aponte, Nilda E.; Department of Marine Sciences; Macchiavelli, Raúl
    A series of cruises were carried out in Mayagüez Bay from January, 1997, to January, 2004, with the purpose of studying phytoplankton dynamics, optically active water components and ultimately developing bio-optical algorithms for the estimation of chlorophyll a (Chl a). Fourth derivative spectroscopic analyses were applied to phytoplankton absorption spectra in order to determine phytoplankton pigments that could be identified as chemotaxonomic markers and to quantify Chl a. The spectral maxima found in the fourth derivative spectra were associated with chlorophylls a, c and carotenoid pigments, probably fucoxanthin. Good correlation was found between in situ Chl a concentration and the fourth derivative peaks associated to photosynthetic pigments. These results suggest that diatoms are the dominant phytoplankton group in Mayagüez Bay. Surface Rrs spectra were modeled with Hydrolight using a four component case 2 model with in situ data for input. The moderate agreement of the model for some of the data was attributed to the error associated with using TSS as a proxy for mineral concentrations. The effect of the bio-optical components concentration on the Rrs curve was then evaluated using Hydrolight. It was determined that for the range of Chl a values normally observed in Mayaguez Bay (0.1 to 1 μg l-1), mineral values over 5 mg l-1 were sufficient to mask the Chl a signal. These results were used to tentatively set a TSS threshold of 5 mg l-1 over which Chl a concentrations cannot be derived from the Rrs spectra. Three empirical algorithms were developed for Mayagüez Bay. When tested with a data set different that the one used for their development, the fourth order polynomial and the red band ratio algorithms produced a 120.15 and 79.00 mean percent error in Chl a estimation respectively. The quasi-analytical algorithm (QAA) from Lee et al. (2002) was also evaluated with Mayagüez Bay data. The QAA performed poorly when the derived inherent optical properties were compared to measured data. The poor performance of the QAA was attributed to its inadequacy in the modeling of the spectral particle backscattering coefficients for Mayagüez Bay.