Development of Macrocystis pyrifera from spores and gametes on artificial substrate. Algal production in a surface culture

This study proposes establishing a methodology for generating algal biomass from spores and gametes of Macrocystis pyrifera (Phaeophyta, Laminariales) on nylon ropes that are 100 m long and 3 mm in diameter, installed on the sea surface. The algae are initially farmed in tanks with seawater of 11°-13°C, pH 8.2, salinity 28-33, radiation 75-100 μmol m -2 s -1 , aeration every 20 min, the addition of nutrients (NaNO3 and Na3PO4), and a 12:12 photoperiod. Twenty days after beginning the cultivation, male gametophytes were 17 μm long by 2.5 μm in diameter, and female gametophytes were 10.5 μm by 7.5 μm. After 60 days of cultivation, the elongated laminar sporophytes were 412 μm by 103 μm. After 195 days, ropes with 2500 µm long sporophytes were installed in the sea at 1 m depth (intermediate cultivation phase), obtaining specimens 36 cm in length after 30 days. Of these specimens, 46 individuals between 30 and 40 cm in size were selected and tied to a 15 m long guide rope that was installed on the surface by means of buoys and anchored to the bottom. After three months, these specimens reached sizes of more than 3 m in length, with abundant laminate biomass surface, reaching an average of 7 kg per specimen, lacking stipes, and with holdfasts of a few centimeters. The surface technique used avoids the herbivory by crustaceans and sea urchins that occurs when the initial developmental stages are done on the seafloor.