Ecological differences among Chilean populations of commercialGracilaria

Field farming ofGracilaria is gradually replacing use of the wild crop in Chile. The most popular planting method consists of establishing underground thallus systems for patches ofGracilaria on wave-sheltered, soft-bottom habitats. Commercial cultivation often involves transplanting vegetative material to distant places along the coast. This study shows that native populations possess some ecological differences that might affect cultivation success. Seven environmental factors were tested for their effects on growth of four geographically separated populations belonging to two species ofGracilaria. No specific or population differences were found under various temperature or salinity regimes. Specific differences occurred in responses to irradiance, daylength, sand burial and sand abrasion. Responses to epiphytes differed among both population and species. Epiphyte recruitment was inhibited by some populations and stimulated by others. Given the farming methods presently used in Chile, these results have ecological and economical importance, as they suggest that transplanting randomly from one to other type of habitat does not assure cultivation success.