Effects of temperature and substrate variations on vegetative growth of spores of the brown alga Sargassum echinocarpum J. Agardh under laboratory conditions

Sargassum echinocarpum J. Agardh is an edible macroalga that is abundant in warm marine waters. This study investigated the effects of temperature and substrate variations on the vegetative growth of its spores under laboratory conditions. Specimens were collected from the southern shallow waters of Abu Dhabi coastal area (Ras Ghanada—UAE) during January 2014. Sargassum echinocarpum showed clear fertile receptacles with multiple attached spores. About 85 % of the total spores released in the sustaining medium were fertilized. The medium containing spores has then cultured in Petri dishes with different bases (clear base, cotton base, and filter paper base) at 25, 30, and 35 °C for 5 weeks. The germlings attained their maximum growth potential at 35 °C, followed by relatively slower growth at 30 °C, and a minimum growth at 25 °C. Moreover, vegetative growth was significantly greater in germlings grown on filter paper substratum, compared to the other substrata (p = 0.02). It has concluded that brown macro-algal spores form during winter in the Arabian Gulf waters and released into the water in order to reach vegetative form during the spring–summer periods, where they attain their maximum growth in May as water temperatures reach 32 °C. It is also concluded that soft or smooth slippery substrata are less preferable for spores to begin germination than rough substrata, represented here as filter paper base.