The influence of major inorganic nutrients on the growth and physiology of high arctic ice algae

A long-term nutrient enrichment bioassay was used to test the hypothesis that silicon is the potential limiting nutrient for growth of bottom ice algae in the Canadian High Arctic and to determine the physiological response of the algae to nutrient deprivation. All measures of algal response (chlorophyll a, particulate organic carbon, cell concentration and carbon allocation) indicated that nitrogen rather than silicon was the principal potential limiting nutrient. Silicon was not present in great excess, however, and significantly influenced the growth of most of the dominant species. Algal growth slowed and ultimately stopped in all treatments except for the combined (P, δi and N) addition. Carbon allocation shifted toward lipid and away from protein as growth was slowed by nutrient depletion, with neutral lipids increasing while membrane-associated lipids declined. There was no evidence of carbon storage in polysaccharides. The biosynthetic response of the algae thus confirmed that nutrient limitation can cause lipid accumulation in ice algal communities.