Growth rate of the carrageenophyte Kappaphycus alvarezii (Rhodophyta, Gigartinales) in vitro

Unialgal cultures were established trom a 2.5 g branch ot a brown variant ot Kappaphycus alvarezii (Doty) Doty ex P. Silva, with the main objective to produce branches for monthly outplanting in the sea. Ditterent conditions were tested to optimize production ot branches in the laboratory. The best growth was obtained under culture conditions of 25 ± 2°C, 170–210 μmol photons m² s^?1, 14:10 LD photoperiod and salinity 32–35‰. Three culture media (Provasoli,‘F/2’and von Stosch) were tested. Deleterious ettects were observed in branches incubated continuously in full‐ or halt‐strength Provasoli's enriched seawater medium (PES). Exponential growth rates ot about 3% day^?1 were obtained using PES, pulse‐fed 24 h per week, or other diluted media used continuously (one‐quarter strength ‘F/2’and half‐strength von Stosch). Laboratory‐grown branches with mean weights from 2.97 to 4.25 g were successfully introduced into the sea at Ubatuba, SP, Brazil (23°26.9′S, 45°0.3′W) an area with mean monthly seawater temperature from 20.3 to 28.5°C (extremes: 17.0–31.0°C). Transplantation of branches produced in unialgal culture, as done in the present study, avoids the risk of introduction of unwanted species into new areas.