Temperature and light responses of alga Caulerpa taxifolia introduced into the Mediterranean Sea

Abstract

Cuttings of Mediterranean Caulerpa taxifolia were cultured under controlled temperature and light conditions in culture chambers. The upper lethal temperature was between 31.5 and 32.5°C and the lower lethal temperature between 9 and 10°C. Between 10 and 12.5°C, the alga survived without any growth; new stolons and new fronds developed at 15 and 17.5°C, respectively. Stolon growth was strongly correlated with the temperature increase. No morphological changes were observed when the cuttings were cultured within the vital temperature range (10 to 31.5°C). The new fronds and stolons developed on the cuttings under a very weak light intensity of photosynthetically active radiation (27 μmol m-2 s-1 at a photoperiod cycle of 14 h light: 10 h dark). The most favorable range of light intensify was between 88 and 338 μmol m-2 s-1 (14 h light: 10 h dark). These light and temperature responses confer to the Mediterranean strain C. taxifolia, introduced in 1984, a large potential for expansion throughout the Mediterranean Sea and also in adjacent tropical and temperate seas.