Determination of the fluorescence quantum yield by oceanic phytoplankton in their natural habitat.

Sun-stimulated chlorophyll a fluorescence has been measured in situ, within the upward and downward light fields, in oceanic waters with chlorophyll concentrations of 0.04-3 mg m(-3). We combined these signals with phytoplankton absorption spectra to derive the fluorescence quantum yield, phi (number of photons emitted by fluorescence/number of absorbed photons). phi was derived separately from hyperspectral (upward and downward) irradiance measurements (with a LI-COR Instruments spectroradiometer) and from nadir radiance near 683 nm (with a Biospherical Instruments profiler). The contribution of inelastic Raman scattering to the signal in the red band was assessed and subtracted. Raman-corrected phi values derived from the two instruments compared well. Vertical phi profiles were strongly structured, with maximal (5-6%) values at depth, whereas phi was approximately =1% in near-surface waters (measurements made approximately at solar noon). These near-surface values are needed for interpretation of remotely sensed fluorescence signals. This optical study shows that the fluorescence yield of algae in their natural environment can be accurately derived in a nonintrusive way with available instrumentation and adequate protocols.

[1]  T. Platt,et al.  Passive fluorescence and photosynthesis in the ocean: implications for remote sensing , 1986 .

[2]  Y. Dandonneau.  Introduction to special section: Biogeochemical conditions in the equatorial Pacific in late 1994 , 1999 .

[3]  L. Prieur,et al.  Analysis of variations in ocean color1 , 1977 .

[4]  E. Fry,et al.  Absorption spectrum (380-700 nm) of pure water. II. Integrating cavity measurements. , 1997, Applied optics.

[5]  J. Kirk.  The upwelling light stream in natural waters , 1989 .

[6]  D. Collins,et al.  The role of reabsorption in the spectral distribution of phytoplankton fluorescence emission , 1985 .

[7]  Ricardo M. Letelier,et al.  Algorithm Theoretical Basis Document Chlorophyll Fluorescence ( MODIS Product Number 20 ) , 1999 .

[8]  A. Morel.  Optical modeling of the upper ocean in relation to its biogenous matter content (case I waters) , 1988 .

[9]  Dale A. Kiefer,et al.  Natural fluorescence of chlorophyll a: Relationship to photosynthesis and chlorophyll concentration in the western South Pacific gyre , 1989 .

[10]  J. H. Morrow,et al.  Evidence for a simple relationship between natural fluorescence, photosynthesis and chlorophyll in the sea , 1990 .

[11]  Motoaki Kishino,et al.  Estimation of the spectral absorption coefficients of phytoplankton in the sea , 1985 .

[12]  R. A. Neville,et al.  Passive remote sensing of phytoplankton via chlorophyll α fluorescence , 1977 .

[13]  J. Gower,et al.  Use of the In Vivo Fluorescence Line at 685 nm for Remote Sensing Surveys of Surface Chlorophyll a , 1981 .

[14]  John Marra,et al.  Analysis of diel variability in chlorophyll fluorescence , 1997 .

[15]  H. Claustre,et al.  Variability in the chlorophyll‐specific absorption coefficients of natural phytoplankton: Analysis and parameterization , 1995 .

[16]  Marcel Babin,et al.  Variability in particle attenuation and chlorophyll fluorescence in the tropical Pacific: Scales, patterns, and biogeochemical implications , 1999 .

[17]  R. Reynolds,et al.  Advances in Understanding Phytoplankton Fluorescence and Photosynthesis , 1992 .

[18]  R C Smith,et al.  Raman scattering and in-water ocean optical properties. , 1990, Applied optics.

[19]  Dale A. Kiefer,et al.  Chlorophyll a fluorescence in phytoplankton: relationship to photosynthesis and biomass , 1985 .

[20]  André Morel,et al.  Diffuse reflectance of oceanic shallow waters: influence of water depth and bottom albedo , 1994 .

[21]  Raymond C. Smith,et al.  Measurements of spectral irradiance underwater , 1970 .

[22]  G. Kattawar,et al.  Exact 1-D solution to the problem of chlorophyll fluorescence from the ocean. , 1982, Applied optics.

[23]  H. Loisel,et al.  Apparent optical properties of oceanic water: dependence on the molecular scattering contribution. , 1998, Applied optics.

[24]  B. Gentili,et al.  Remote sensing of sea surface Sun-induced chlorophyll fluorescence: consequences of natural variations in the optical characteristics of phytoplankton and the quantum yield of chlorophyll a fluorescence , 1996 .

[25]  A. Bricaud,et al.  Spectral absorption coefficients of living phytoplankton and nonalgal biogenous matter: A comparison between the Peru upwelling areaand the Sargasso Sea , 1990 .

[26]  Annick Bricaud,et al.  Spatial variations in the chlorophyll‐specific absorption coefficients of phytoplankton and photosynthetically active pigments in the equatorial Pacific , 1997 .

[27]  Charles S. Yentsch,et al.  A bridge between ocean optics and microbial ecology , 1989 .

[28]  T. G. Owens.  Energy Transformation and Fluorescence in Photosynthesis , 1991 .

[29]  H. Gordon,et al.  Diffuse reflectance of the ocean: the theory of its augmentation by chlorophyll a fluorescence at 685 nm. , 1979, Applied optics.

[30]  G. Krause,et al.  Chlorophyll Fluorescence and Photosynthesis: The Basics , 1991 .

[31]  Marcel Babin,et al.  Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters: Analysis and implications for bio-optical models , 1998 .