Relationship between bio-optical characteristics and photoinhibition of phytoplankton

Abstract

The relationship between the bio-optical properties of different microalgae and photoinhibition after short-term exposure (15 and 30 min) to solar radiation was analyzed. Photoinhibition was determined as the decrease in oxygen production and in the in vivo-induced chlorophyll fluorescence. Microalgae with different chlorophyll concentrations, cell size and volume were used. Both photoinhibition and recovery of oxygen production and quantum yield were higher after 30 than after 15 min exposure to solar radiation. Photoinhibition was reduced when UV-A and UV-B radiations were eliminated from the solar radiation. The decrease of effective quantum yield and oxygen production was not dependent on cell size, biovolume or chlorophyll concentration in the algal cultures. It was, however, related to the bio-optical property of the cultures, manifested as the specific attenuation coefficient (Kc). As a general response, the inhibition of effective quantum yield slightly decreased with the increase in Kc. Recovery of yield and oxygen production in darkness after exposure to solar radiation was also clearly related to Kc. The relation between the recovery of the yield and Kc followed a parabolic function. It was also found that the recovery of the inhibition of the yield was higher in phytoplankton with active xanthophyll cycle but that it was not dependent on the concentration of total carotenoids.