Potential of temperature- and salinity-driven shifts in diatom compatible solute concentrations to impact biogeochemical cycling within sea ice

• Published in: Elementa: Science of the Anthropocene
• Main Authors: Dawson, Hannah M., Heal, Katherine R., Boysen, Angela K., Carlson, Laura T., Ingalls, Anitra E., Young, Jodi N.
• Other Authors: Helmig, Detlev, Arrigo, Kevin
• Format: Article in Journal/Newspaper
• Language: English
• Published: University of California Press 2020
• Subjects: Arctic; Antarctic; The Antarctic; Antarc*; ice algae; Sea ice
• Online Access: http://dx.doi.org/10.1525/elementa.421; http://online.ucpress.edu/elementa/article-pdf/doi/10.1525/elementa.421/441575/421-7239-1-pb.pdf

Sea-ice algae are an important source of primary production in polar regions, yet we have limited understanding of their responses to the seasonal cycling of temperature and salinity. Using a targeted liquid chromatography-mass spectrometry-based metabolomics approach, we found that axenic cultures of the Antarctic sea-ice diatom, Nitzschia lecointei, displayed large differences in their metabolomes when grown in a matrix of conditions that included temperatures of –1 and 4°C, and salinities of 32 and 41, despite relatively small changes in growth rate. Temperature exerted a greater effect than salinity on cellular metabolite pool sizes, though the N- or S-containing compatible solutes, 2, 3-dihydroxypropane-1-sulfonate (DHPS), glycine betaine (GBT), dimethylsulfoniopropionate (DMSP), and proline responded strongly to both temperature and salinity, suggesting complexity in their control. We saw the largest (> 4-fold) response to salinity for proline. DHPS, a rarely studied but potential compatible solute, had the highest intracellular concentrations among all compatible solutes of ~85 mM. When comparing the culture findings to natural Arctic sea-ice diatom communities, we found extensive overlap in metabolite profiles, highlighting the relevance of culture-based studies to probe environmental questions. Large changes in sea-ice diatom metabolomes and compatible solutes over a seasonal cycle could be significant components of biogeochemical cycling within sea ice.