1Department of Fisheries, Faculty of Fisheries, Kagoshima University, Shimoarata, Kagoshima 890-0056, 2Institute for East China Sea Research, Nagasaki University, Taira, Nagasaki 851-2213, Japan
The photosynthetic characteristics of five Sargassum species (Fucales): S. piluliferum, S. patens, S. fusiforme, S. crispifolium and S. alternato-pinnatum, were determined over a range of temperatures (10-36℃) by a dissolved oxygen meter and a pulse amplitude modulation chlorophyll fluorometer. Samples for the experiments were collected during April to June 2010 at Sakurajima, Kagoshima Prefecture, Japan, located within Kagoshima Bay. The net photosynthetic rate of each species was highest from 20℃ to 24℃. An ANOVA analysis indicated that there were no significant differences from 16℃ to 28℃ for temperate species (S. piluliferum, S. patens and S. fusiforme) and from 16℃ to 24℃ for subtropical species (S. crispifolium and S. alternato-pinnatum). The relative electron transport rate (rETR) of photosystem II (water/plastoquinone oxido-reductase) of each species increased with increasing temperature, was greatest between 28℃ to 30℃, and decreased at temperatures above 32℃. Summer seawater temperature is around 29℃ at Sakurajima, suggesting that the electron transport might not be damaged under natural conditions. However, temperatures above 30℃ might influence its photosynthetic activity.