The present paper describes growth dynamics in a natural bed of the resource `luga negra' (Sarcothalia crispata) in Guapilinao, southern Chile (41 °57' S, 73°31' W) . This resource is currently harvested and exported as raw material for the production of carrageenan . Seasonal variation in biomass, frond size, density and phenology was determined by periodic sampling . Natural recruitment was evaluated on different substrata added to the field ; at the same time, substrata were inoculated under greenhouse conditions . Results showed that 'luga negra' has seasonal growth : biomass increased from a minimum in spring to a maximum in mid to late summer . On the other hand, density was minimal in winter (200 ind . m_2) and increased to 2000 ind . M-2 in late spring . Peak abundance of mature tetrasporic fronds occurred in late summer, whereas that of cystocarpic fronds occurred in winter . Recruitment began in summer and extended into winter . Survival on different substrata were compared . Gametophytes had better survival rates on clam shells and 5 mm rope while tetrasporophytes had the best survival rate on clam shells and secondarily on boulders .