Use of chlorophyll fluorescence to estimate the effect of photoinhibition in outdoor cultures of Spirulina platensis

Chlorophyll fluorescence measurements were used to evaluate the effect of temperature on photoinhibition in Spirulina platensis cultures grown in tubular reactors outdoors. Cultures grown at 35 °C during the day time showed a lower reduction in the Fv/Fm ratio as compared to cultures grown at 25 °C. It is demonstrated that the lower temperature photoinhibited cells can undergo a complete recovery once transferred to low light and higher temperature. This recovery does not take place when 100 ug ml-1 chloramphenicol is added to cells. The recovery is light dependent and cells incubated in the dark at low temperature do not show a recovery in the Fv/Fm ratio. The data presented strongly support the hypothesis that photoinhibition takes place in outdoor Spirulina cultures. At the same time it is demonstrated that fluorescence measurements can be used as a fast reliable indication for photoinhibition in outdoor algal cultures.