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Abstract
Isolates of Haslea ostrearia containing different amounts of marennine have been investigated to elucidate the physiological role of this enigmatic blue pigment. Fluorescence analyses at room temperature and 77K showed that marennine is not involved in light-harvesting for either PS II or PS I. On the other hand, a light-shielding function of marennine was observed. With marennine present, the cells behaved similarly to organisms which are adapted to an unfavourable environment, i.e. conditions under which growth is hampered; as a result, the photosynthetic machinery needs protection from potential harmful light doses. Photosynthetic oxygen-evolution versus light intensity measurements supported the results of the fluorescence analysis, in that no lethal or sublethal damage of marennine-containing cells was observable after treatment with strong light The importance of such an unusual pigment that shields red-light is discussed for organisms such as diatoms and brown algae that contain light-harvesting carotenoid complexes.