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 degrees to 20 degrees C and from 2 degrees to 30 degrees C, respectively. The width of the growth range of each species. also varied from 3.8 degrees to 25 degrees C, and the growth of these species was observed, as a whole, between a wide temperature range from -1.8 degrees to 30 degrees C.
Within the growth temperature ranges, the growth rate of each species increased with temperature until reaching a maxim urn, 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 zipper 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 Q(10) = 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.