Rhythms of a changing ocean: Chronobiology and control of reproduction in marine organisms

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Life and its rhythms evolved in the sea, yet our understanding of biological rhythms largely revolves around circadian and seasonal cycles in terrestrial models. My research on marine organisms strives to elucidate key interplays in cyclic life-history events, following an integrated view that combines the perspectives of chronobiology (relation between biological activity and time), phenology (relation between periodic events and climatic conditions) and evolutionary biology (adaptive benefits of biological rhythms). My long-term objective is to clarify the mediators and adaptive significance of reproductive periodicities in benthic populations. Recently we found that 24 boreal species belonging to 6 phyla undergo seasonal and lunar rhythms of reproduction with mass-spawning events similar to coral reefs, although species-specific diel components preserve reproductive isolation. We also found that deep-sea species, presumably exposed to little environmental variability, still exhibit seasonal and lunar breeding cycles. Currently proposed mechanisms and advantages of rhythmic reproductive events cannot fully explain why so many species release progeny in spring, irrespective of reproductive mode (free spawning, brooding), larval type (feeding, nonfeeding), depth or region. The short term objectives of the proposed program are to: 1) further investigate breeding periodicity in deep-sea species; 2) compare the adaptive value of periodic reproduction in species with different life histories; 3) tease out the drivers of breeding rhythms in deep-sea and boreal taxa; 4) investigate the concept of "sentinels" (organisms more receptive to environmental cues); and 5) identify circadian rhythms in species with seasonal breeding. By integrating concepts of reproductive biology, chronobiology and chemical ecology we hope to disentangle the respective roles played by biological clocks, external cues and social interactions and gain a finer understanding of benthic ecosystem functioning. Identifying the drivers of multileveled biological rhythms in marine taxa will not only provide insight into our evolutionary past but also help develop aquaculture techniques and time-scale-based management and conservation strategies. ****