IB02-22 POSTER

LIGHT ABSORPTION COEFFICIENT, QUANTUM YIELD, AND PHYTOPLANKTON PHOTOSYNTHETIC PARAMETERS IN THE SOUTHERN REGION OF THE CALIFORNIA CURRENT

R.SOSA-AVALOS (Universidad de Colima, km. 20 carret. Manzanillo-Cihuatlán, Manzanillo, Colima. México, rsosa@cicese.mx); B. G. Mitchell (Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0218, USA, gmitchell@ucsd.edu); G. Gaxiola-castro (Departamento de Ecología, Centro de Investigación Científica y de Educación Superior de Ensenada, km. 107 carret. Tijuana-Ensenada, Ensenada, Baja California, México, ggaxiola@cicese.mx)

During four 1999 seasons, oceanographic surveys within the Mexican Investigations of the California Current (IMECOCAL) program were carried out. Phytoplankton Chlorophyll a concentration, and particulate light absorption both retained in GF/F filters from samples collected at six light levels were determined. Also, we generated photosynthesis-irradiance curves (P-E) to obtain phytoplankton photosynthetic parameters (a * and P*max), from the 50%E0 depth. Surface Chlorophyll concentration range from 0.12 mg× m-3 during fall to 3.08 mg× m-3 in spring. Mean annual particulate absorption coefficients values were 0.034 m-1 [ap (444)], and 0.0091 m-1 ap (674). ap (444) increases in relation with Chlorophyll concentration during the winter, spring and summer cruises. However, during the fall cruise this pattern was not present, which mean that other materials different that phytoplankton were absorbing light. In addition, we observed that ap(674) increase with Chlorophyll ! concentration in the four cruises. We observed that our ap(444), and CalCOFI data both increase with the Chlorophyll concentration, except some values of the fall cruise. While our data and CALCOFI data of ap(674) both increase with Chlorophyll concentration. In general, the initial slope (a *) changes from 0.002 to 0.054 mgC (mgChla)-1 h-1 (m mol photons m-2 s-1)-1. Mean maximum quantum yield (f max) was 0.042 mol C (mol photons)-1, with the lower values for summer, and the higher in spring, with the same trend that for a *. While the variation of P*max was from 1.04 to 16.09 mgC(mgChla)-1h-1. Our a * values were similar that the reported before by the California Current, with slightly higher values for P*max.