Metabolic Regulation of Sea-Ice Diatoms in Response to Temperature and Salinity Could be a Significant Contributor to Dissolved Organic Matter Cycling Within Sea-Ice.

Abstract:

Intense bottom-ice algal blooms, dominated by diatoms are an important source of food for grazers, organic matter for export during sea ice melt, and dissolved organic carbon. Sea-ice diatoms have a number of adaptations, including accumulation of compatible solutes, that allow them to inhabit a highly variable environment characterized by extremes in temperature, salinity and light. In addition to protecting them from extreme conditions, these compounds present a labile, nutrient-rich source of organic matter and include precursors to climate active compounds (e.g. DMS), which are strongly regulated over the seasonal cycle of formation and melt of sea ice. Here we will show laboratory and field studies quantifying nitrogen- and sulfur-containing compatible solute concentrations in response to shifting temperature and salinity in sea-ice diatoms. We find intracellular concentrations of some compounds of ~1M, evidence of strong regulation in response to changing temperature and salinity, and rapid release of solutes into the environment during ice melt. Taken together, these results suggest that regulation of compatible solutes by sea-ice diatoms in response to seasonal or long-term environmental change could significantly impact dissolved organic matter cycling within sea-ice.