Growth phase-specific release of polyunsaturated aldehydes by the diatom Skeletonema marinoi

Polyunsaturated aldehydes (PUAs) have been extensively studied for their potential role in phytoplankton defence against grazers, but recently a potential infochemical role has been identified as well. We present here the first evidence of a synchronized release of PUAs from intact cells of a culture of the diatom Skeletonema marinoi. The release occurs transiently before the culture changes to the decline phase, providing a time-limited potential signal. When cultures are exposed during different stages of growth to PUAs in concentrations found in the medium, no general responses were found. However, a weak effect on cell concentration is observed exclusively when cultures in the late stationary phase are challenged with PUAs. Our results support for the first time the experimentally postulated hypothesis that PUA can play a role as infochemicals in mediating plankton interactions.