Effect of temperature on changes in size and morphology of the marine diatom, Ditylum brightwellii (West) Grunow (Bacillariophyceae)

• Different morphological types of Ditylum brightwellii (Prism and Cylinder types).
• Temperature-induced size and morphological changes in D. brightwellii.
• The change might provide a competitive advantage by bypassing sexual reproduction.

The objective of the present study was to assess size and morphological changes in response to temperature in the marine diatom, Ditylum brightwellii (West) Grunow, using ecological, morphological and physiological approaches. D. brightwellii has two distinct cell morphologies: prism (large-sized cell) and cylinder types (small-sized cell). In the coastal waters of South Korea, the prism type was found to be present at high frequency at low temperatures, whereas the cylinder type was predominant at high temperatures. Other environmental factors did not affect the presence of either cell type significantly. In growth experiments to determine the effect of temperature on the size of D. brightwellii, the abundance of the prism type increased at low temperature, but the abundance of the cylinder type increased at high temperature. These results are important for understanding temperature-induced size and morphological changes in D. brightwellii, and their potential role as an adaptive strategy.