Seasonal and spatial characterization of the Gulf of California phytoplankton photosynthetic parameters

Abstract

Photosynthesis-irradiance and phytoplankton absorption data from waters of the central Gulf of California, as well as data in the literature, were analyzed in order to propose working averages of the physiological parameters of phytoplankton to estimate primary productivity at large time and space scales. Since there is substantial variability within data sets, we conclude that it is not possible at this time to predict fine time- and space-scale variation in photosynthetic parameters. We recommend the following working averages for the whole Gulf of California and for "winter" conditions (surface TºC <22ºC): a surface P*_max = 9.6 ± 2.4 mgC mgChl^–1 h^–1 (assimilation number), with a linear variation between this and 3.7 ± 0.3 at the middle of the euphotic zone (ez), and then a constant value for deeper waters; a single value of α*_inc = 0.029 ± 0.004 mgC mgChl^–1 h^–1 (μmol quanta m^–2 s^–1)^–1 (incubator´ s initial slope); and φ_max = 0.06 ± 0.01 molC (mol quanta)^–1 (quantum yield of photosynthesis). For "summer" conditions we recommend: a surface P*_max = 3.7 ± 0.3, with a linear variation between this and 1.5 ± 0.2 at the middle of the ez, and another linear variation between the latter and 0.4 ± 0.1 at the bottom of the ez; a surface α*_inc = 0.013 ± 0.001, with a linear variation between this and 0.001 at the bottom of the ez; and a single value φ_max = 0.014 ± 0.002. A procedure is given to correct α*_inc for the in situ spectral distribution of light to obtain α*_{in situ}.