Glass aquaria of 20 L, divided into

Glass aquaria of 20 L, divided into two independent compartments of 10 L each, were used. In each compartment, four PVC cylinders of 60 mm in diameter were placed in a vertical position as previously noted by Gutiérrez et al. (2006). To each cylinder, 15 m of polypropylene rope (3 mm ø) was attached. One liter of zoospore solution was added to each aquarium compartment. During the first 78 h, the aquariums remained without aeration and under controlled conditions of temperature (15±1°C), of photon flux density (50±10 μmol photons m−2 s−1), provided by two fluorescent lights (40 W), and of photoperiod of 12:12 h (L/D) in order to allow spore settlement. After this period, the first change of seawater and culture media, enriching the seawater with a solution of von Stosch medium (Oliveira et al. 1995), was carried out. The cultivation conditions, described above, were the same, but with permanent aeration. The second change of enriched seawater was on the 15th day of cultivation, and then the aquarium content was renewed weekly. GeO2 (3 μg L−1) was added when diatoms were observed. The cultures were kept in the laboratory for 2 months until sporophytes reached an approximate length size of 5±1 mm and a density of 40±18 fronds cm−1.