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The yield and the quality of carrageenan depend, among other things, on the cultivar or strain and on the cultivation and processing techniques. This work presents carrageenan yields and some properties of Kappaphycus alvarezii under selected cultivation conditions i.e. cultivation period, depth and planting density. Growth rates (GR) ranged from 5.2-7.2% day −1 , with the highest GR at 28 days, at 0-0.5 m depth, and planting density of 12 and 8.4 plants m −2 . Highest productivity was observed in samples after 44 and 59 day cultivation period, which were grown at 0-0.5 m depth, and a planting density of 24 plants m −2 . Carrageenan yields, iota fraction, viscosity, molecular weight and gel strength were measured. A cultivation period of 28 days during the winter had a significant higher carrageenan yield, while samples from 59 days showed a significantly higher iota fraction. Carrageenan also presented an increasing molecular weight under longer cultivation periods. A similar trend was observed for viscosity and gel strength. All samples cultivated in Brazil gave higher values when compared to a K. alvarezii commercial reference sample, with the exception of carrageenan yield values, which were lower in this study. Taking into account all parameters, the culture condition which provided the best carrageenan from a commercial perspective were 45 days of cultivation, growing at the surface, with a planting density of 12 plants m −2 . Considering that this study was performed in the least favorable season (winter), these results indicate that the site is suitable for the implementation of commercial cultivation.

Based on their distinct physiological characteristics, we postulated that different strains of Gracilaria birdiae (Gracilariales, Rhodophyta) would have distinct performances when grown in the sea. Samples from a northeastern Brazil population, including red (RD-CE), greenish-brown (GB-CE), and green (GR-CE) strains, and one red strain (RD-ES) from a southeastern population were cultivated in Ubatuba Bay, southeastern Brazil. We analyzed the survival ability, growth rate, and the agar yield and quality of these strains. The growth rates (GRs) and seawater temperatures were measured for 16 months. The northeastern population strains were in good condition during all the cultivation periods, while the RD-ES strain had a lower GR and died during some time periods. Overall, the GR ranged from 0.4% to 4.4% day-1, depending on the strain and the period of cultivation. The GRs of the RD-CE, GR-CE, and GB-CE strains were similar during all the cultivation periods. The increased GR in all the strains of G. birdiae seemed to be related to a slight rise in the seawater temperature. However, the GRs decreased in all the strains when the temperatures remained high for the protracted periods. In addition to their similar GRs, the RD-CE and GR-CE strains had similar yields and qualities as the polysaccharides. We concluded that these three strains are suitable for testing as the candidates for future commercial cultivation.

SUMMARY 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.

Hypnea musciformis is the only species so far exploited in Brazil as raw material for the production of k-carrageenan. Due to the erratic production in space and time, increasing harvest and transportation costs, experiments have been performed in order to assess the viability of H. musciformis mariculture.In nature the species occurs as an epiphyte, and so mariculture using artificial substrates that simulated the natural host of the species was tried. These substrates were attached, at regular intervals, to linear ropes. In the sea, these ropes were stretched between cement blocks. Seeding occurs naturally, by means of spores, or detached pieces of H. musciformis scattered in the water column that get entangled on the ropes. The best yields (0.54 wet kg m -month -) were obtained with unthreaded rope substrates maintained in a vertical position by small rafts. Production is highest in the first 18 m off the rocky shore (0-2.1 m deep), at the highest substrate density utilized (10 m-1), 2-3 months after installing the ropes in seawater. The main factor controlling seasonal production is water movement.

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