The red alga Chondracanthus exasperatus is a source of the phycocolloid carrageenan as well as an ingredient referred to as "intralamellar gel" in a recently developed cosmetic formula (U.S. Patent 6,136,329). The high value of the cosmetic product has sparked renewed interest in cultivation of this species. Previous cultivation methods for this species include open water culture on nets and immersed cultivation in tanks supplied with flow-through pumped seawater. The installation of a high capacity seawater supply, pumping and drain system is a major cost for flow through systems. Recirculating or re-use seawater systems that minimize seawater turnover may offer significant cost savings over single-pass, flow through seawater systems. In this research several options for minimizing seawater use have been tested: recirculating batch culture in which nutrient replenished (carbon dioxide and mineral nutrients) natural or artificial seawater is used with minimal turnover and spray culture in which plants are suspended in air saturated with nutrient replenished natural or artificial seawater medium. Small volume (<2 L), single-plant bioreactors and larger multi-plant, 20, 80 and 320 L (sea water volume) immersion and spray systems have been developed and tested. Results from these systems will be presented. Research supported by Washington Sea Grant, Washington Biotechnology Center and Soliv International Corporation.

Key words: aquaculture, Chondracanthus exasperatus, culture, recirculating, red alga, seaweed