Acclimation of Antarctic bottom-ice algal communities to lowered salinities during melting

Sea-ice brine algal communities were exposed to salinities between 30 and 10‰ during melting. There was a progressive decline in maximum quantum yield, relative electron transfer rate (rETRmax) and photosynthetic efficiency (α) with decreasing salinity of the final melted sample. While all species showed a drop in these parameters, Fragilariopsis curta and Entomoneis kjellmannii showed the least inhibition. There was a steady increase in rETRmax and α over 5 days after melting, especially in the samples melted into the highest salinities. In addition, the samples melted from the ice without added filtered seawater showed no photosynthetic activity after 2 days. Our results suggest that for experimental work using sea-ice microalgae, the final salinity of the melted sample should be greater than 28‰ (i.e. the ratio of sea ice to filtered seawater should be at least 1:2).