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Keywords:

  • Arctic;
  • Bacillariophyceae;
  • growth rates;
  • specific growth;
  • temperate;
  • temperature

ABSTRACT

Eight diatom species (Chaetoceros pseudocurvisetus Mang., Stephanodiscus hantzschii Grun., Skeletonema costatum (Grev.) Cleve, Asterionella formosa Hass., Thalassiosira nordenskioeldii Cleve, Detonula confervacea (Cleve) Gran, Chaetoceros sp., and Nitzschia frigida Grun.) were isolated from various temperature environments ranging from temperate to the Arctic, and their growth responses to temperature were determined. Each species grew over a different temperature range. The lower and upper limits of each species varied from −1.8° to 20° C and from 2° to 30° C, respectively. The width of the growth range of each species. also varied from 3.8° to 25° C, and the growth of these species was observed, as a whole, between a wide temperature range from −1.8° to 30° C.

Within the growth temperature ranges, the growth rate of each species increased with temperature until reaching a maximum, which was followed by a steep decrease up to the upper limit of the growth range. As a result, each species showed a maximum rate at the temperature very near to the upper limit, which was generally higher than the isolation temperature. The specific growth rates were compared among the eight species. The interspecific maximum rate at each temperature exhibited an exponential increase with a Q10=1.48. The relative growth rates of each species were calculated by normalizing the specific growth rates with the interspecific maximum rate at each respective temperature. The higher relative growth rates tended to occur at the isolation temperature of each species, suggesting that temperature is a significant control on species distributions in nature.