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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps13950

Daylength influences reproductive success and sporophyte growth in the Arctic kelp species Alaria esculenta

Neusa Martins*, Luís Barreto, Inka Bartsch, Julien Bernard, Ester A. Serrao, Gareth A. Pearson

*Corresponding author:

ABSTRACT: Many organisms have endogenous clocks that synchronize biological processes with environmental changes leading to optimized development and reproduction. However, certain environments like the Arctic pose a special challenge to circadian clocks, particularly due to the extreme seasonal changes in daylength, ranging from permanent sunlight to complete darkness. Kelps seem to be well adapted to the variable environmental conditions characteristic of this region. However, daylength might affect kelp species that use circadian rhythms to control the timing of daily egg release from female gametophytes. We aimed to investigate how daylength and light intensity affect gametogenesis and reproductive success of summer reproducing kelp species (using Alaria esculenta as model). As daylength and temperature co-vary most part of the year, we also aimed to investigate the thermal resilience of the sporophytes developed under different daylengths to understand if there is a cross-tolerance between light doses and temperature tolerance. Although continuous daylight, characteristic of Arctic summers, enhanced gametogenesis and increased gametophyte vegetative growth and thereby the number of potential reproductive gametophyte cells, sporophyte production was higher under long (16:8h) and intermediate (12:12h) days. Sporophyte growth was triggered by changing daylength from short to long days, suggesting a synchronization with the annual daylength variation. High daily light doses during reproduction and early development improved the subsequent sporophyte survival at high (sub)lethal temperatures, indicating cross-tolerance between light and temperature. Reproductive success in Arctic A. esculenta was hampered under continuous light, and we hypothesize that this might result from disturbance of synchronized egg release and subsequent fertilization.