GROWTH IRRADIANCE AS A FACTOR CONTROLLING THE DARK RESPIRATION RATES OF MARINE-PHYTOPLANKTON

Respiration rates normalized to chlorophyll a of laboratory cultures of Brachiomonas sp., Gyrodinium aureolum, Synechococcus sp. (clone WH 7803), Pycnococcus provasolii (clone W48-23) and Phaeocystis sp. showed a positive relationship with growth photon flux density (I(g)). It is argued that this constitutes an energy conserving strategy of adaptation to conditions of low irradiance. The ratio of respiration to light-saturated rate of photosynthesis (R/P(max)) also showed a decrease with decreasing I(g). Algal cell size, within the investigated range (0.2 to 1380 pg C cell-1), showed little influence on biomass-specific respiration rates.