Effects of Temperature and Light Intensity on the Gametophyte Fragment Growth of Ecklonia cava Kjellman (Laminariales, Phaeophyta)

Abstract

We examined the effects of temperature and light intensity on gametophyte growth of Ecklonia cava Kjellman. The growth of female and male gametophytes was investigated before maturation. Gametophytes prepared from Munseom, Jeju, Korea in October 2014 were separated by sex and maintained under the following conditions: 15°C, 20 µmol•m -2 •s -1 , and a 12-h/12-h light/dark cycle. The experiments were conducted at five temperatures (10, 15, 20, 25, and 30°C) and three light intensities (5, 20, and 40 µmol•m -2 •s -1 ). Daily growth rates were estimated by the increase in filamentous frond area. The optimal growth conditions for female gametophytes were 20°C and 40 µmol•m -2 •s -1 ; the optimal conditions for male gametophytes were 15°C and 20 µmol•m -2 •s -1 . The relative growth rates (RGR) of female and male gametophytes decreased at 25°C and 30°C, respectively. At 30°C, RGRs of gametophytes decreased by approximately 1.0% day -1 . In addition, RGRs of male gametophytes were higher than those of female gametophytes. These results indicate that female gametophytes were more sensitive to temperature and light intensity than male gametophytes. Moreover, these results suggest that E. cava growth rates could decrease as a result of global warming.