Phytoplankton spectral absorption in the Southern Ocean: preliminary results from SO-GASEX
Bruce
Robert
Hargreaves, Lehigh University, brh0@lehigh.edu
(Presenting)
We will present preliminary data on phytoplankton spectral absorption (300-750nm) from the SO-GASEX cruise (28 February - 9 April, http://so-gasex.org/index.html). Comparisons will be made among separate but closely-linked projects (other PI's: Zhongping Lee, John Marra et al.). Ultimate goals include establishing the accuracy of alternative methods for measuring phytoplankton spectral absorption, modeling photosynthesis from in situ and remotely sensed data that quantify phytoplankton spectral absorption, and contributing phytoplankton productivity data to an improved model for air-sea flux of carbon dioxide.
One specific objective for which preliminary results will be presented is comparison of three methods for measuring particle and pigment absorption. Preliminary comparisons will also be presented for matched measurements of (1) water leaving radiance (Zhongping Lee), (2) quantum yield via FRRF, (3) extracted chlorophyll a (John Marra et al.), and (4) multiple fluorescence signals (CDOM and in vivo phytoplankton pigments) from an improved version of Turner Designs C6 fluorometer (Hargreaves).
Measurements of phytoplankton absorption during the cruise will primarily use a new portable instrument (pQFT-TR) to implement Tassan and Ferrari's transmittance/reflectance method of measuring particle and pigment absorption for paricles concentrated on GF/F filters. The new method uses appropriate corrections for fluoreescence artifacts and maximizes processing speed and accuracy while minimizing sample handling. Comparison with the Filter-Transfer-Freeze method (which minimizes scattering artifacts) will be made during the cruise on selected samples.
Post-cruise analysis to be presented at a later date will include additional calibration of the qQFT-TR instrument and comparisons with consortium measurements and modelled data (reconstructed pigment absorption based on HPLC pigment concentrations, spectral absorption of particles using flash-frozen GF/F filters using qQFT-TR and a standard spectrophometer, and satellite-derived estimates of phytoplankton absorption matched to cruise measurements).
NASA Carbon Cycle & Ecosystems Active Awards Represented by this Poster: