Daily Photosynthetic Parameters and Biomass from Size-Fractionated Phytoplankton off Baja California

Daily photosynthetic parameters of phytoplankton were determined from water samples collected in the coast of Baja California, during 26 June to 10 July 1986. Samples were incubated with C14 to generate photosynthesis-irradiance curves (P-E) and fractionated into two size classes, using simultaneous filtration with 8 and 0•45 μm membrane filters. At the same station temperature, salinity, nitrate, nitrite, phosphate, silicate, chlorophyll and phytoplankton abundance were measured. All variables suggested two strong mixing events, one at the beginning and another at the end of the sampled period. In general, the initial slop (aB) of the P-E curves and the light-saturated rate (PBm), both showed low values during the mixing period and higher values during the stratification time. Stratification in the water column appeared to be an important factor controlling the variability of the photosynthetic parameters in the phytoplankton greater than 8 μm size. PBm and aB from the phytoplankton smaller than 8 μm, did not show any relationship with the parameter of stratification in the water column.