Effect of temperature on photosynthesis-light response and growth of four phytoplankton species isolated from a tidal freshwater river

Three cyanobacteria (Microcystis aeruginosa Kutz, emend, Elenkin, Merismopedia tenuissima Lemmermann, and Oscillatoria sp.) and one diatom (Aulacoseira granulata var, angustissima O. Mull. emend, Simonsen) were isolated from the tidal freshwater Potomac River and maintained at 23 degrees C and 40 mu mol photons . m(-2) . s(-1) on a 16:8 L:D cycle in unialgal culture, Photosynthetic parameters were determined in nutrient-replete cultures growing exponentially at 15, 20, 25, and 30 degrees C by incubation with C-14 at six light levels. P-max(B) was strongly correlated with temperature over the entire range for the cyanobacteria and from 15 to 25 degrees C for Aulacoseira, with Q(10) ranging from 1.79 to 2.67. The alpha values demonstrated a less consistent temperature pattern, Photosynthetic parameters indicated an advantage for cyanobacteria at warmer temperatures and in light-limited water columns. p(max)(B) and I-k values were generally lower than comparable literature and field values, whereas a was generally higher, consistent with a somewhat shade acclimated status of our cultures. Specific growth rate (mu), as measured by chlorophyll change, was strongly influenced by temperature in all species, Oscillatoria had the highest mu at all temperatures, joined at lower temperatures by Aulacoseira and at higher temperatures by Microcystis, Values of mu for Aulacoseira were near the low end of the literature range for diatoms consistent with the light-limited status of the cultures. The cyanobacteria exhibited growth rates similar to those reported in other studies. Q(10) for growth ranged from 1.71 for Aulacoseira to 4.16 for Microcystis, Growth rate was highly correlated with P-max(B) for each species and the regression slope coefficients were very similar for three of the species.