Acclimatization of diatom Phaeodactylum tricornutum to long-term environmental temperature and light intensity changes

Abstract

Diatoms are the dominant primary producers in a number of oceanographic settings that require high-nutrient and turbulent conditions. In addition, diatoms are sensitive indicator of environmental changes and small modifications of environment result in measurable changes in physiological and biochemical parameters. In the present study the model diatom species, Phaeodactylum tricornutum, was culturing for 6 months and the influence of two environmental factors i.e. temperature and light intensity, as the model of greenhouse effect, was tested. Two temperatures i.e. 12°C (low) and 20°C (moderate), and two light intensities i.e. 6μ Em-2s-1 (low) and 40 μEm-2s-1 (moderate) were selected. Three main growth phases of diatom cultures were observed. In the first phase (first two weeks) the optical density at 600 nm (OD) of cultures as well as photosynthetic activity measured as Fv/Fm parameter, increased under all experimental conditions. However, in third growth phase i.e. after four months of experiments, the decrease of OD was detected only at a higher temperature. Values of Fv/Fm parameter showed that photosynthetic activity of P. tricornutum was more sensitive to light intensity than to growth temperature and lower photosynthetic activity was detected at moderate light intensity. In the third phase photosynthetic activity was also well correlated with chlorophyll a concentration and the carotenoid content. The obtained results indicated that the growth rate of diatom cultures depends on temperature whereas photosynthetic activity is more sensitive to light intensity. Low temperature as well as low light intensity were found to be better environmental conditions which ensure a sustainable and long-term growth of diatoms.