| Abstract: | Three axenic polar sea ice diatom cultures were subjected to a 30 day simulated summer-winter transition in which light and temperature were decreased and salinity was increased to mimic seasonal changes previously reported for ice-covered polar seas. The diatoms responded to these changes by a reduction in cellular metabolism as indicated by: 1) A decline in growth rate and photosynthetic rate; 2) a decrease in cellular ATP; and 3) the storage and subsequent utilization of endogenous carbon reserves. In addition, heterotrophic potential of the three clones increased by as much as 60-fold. In some cases, the decrease in light intensity characteristic of the onset of polar winter was alone sufficient to trigger these physiological changes. |
