MEPS prepress abstract  -  DOI:

Pigment composition and photoprotection of Arctic sea ice algae during spring

Virginie Galindo*, Michel Gosselin, Johann Lavaud, CJ Mundy, Brent Else, Jens Ehn, Marcel Babin, Søren Rysgaard


ABSTRACT: From the beginning of spring to the melt period, ice algae in the bottom of Arctic sea ice experience a large irradiance range, varying from <0.1% up to 25–30% of the incoming visible radiation. The increase in spring is usually rapid with a varying photoacclimative response by bottom ice algae to protect them against excess light, such as changes in cellular pigment composition. This study focuses on the temporal variation in pigment composition of ice algae under 2 contrasting snow depths (thin and thick) during spring. Controlled experiments were also carried out to investigate the photoprotective capacity of ice algae to relatively high irradiances during a short-term period (<6 h). Bottom ice algae were able to photoacclimate rapidly and effectively to an irradiance ranging from 10 to 100 µmol photons m2 s1. However, we observed contrasting responses in photoacclimation depending on the ice algal community composition and their light history. Our experimental results suggest that the xanthophyll cycle (diadinoxanthin to diatoxanthin conversion) and the D1-protein recycling play an important role to stabilize photoprotection in ice algae. In addition, bottom ice algae likely employed a ‘cellular light-exposure memory’ strategy in order to improve their photoacclimative response to changing light exposure. According to our data, this process could be maintained over at least 2 weeks. Hence, ice algae may be more resilient to varying light conditions than previously thought and well adapted for future expected light regime changes associated with variability in snow and sea ice cover.