INTERTIDAL CULTIVATION OF GRACILARIA-CHILENSIS (RHODOPHYTA) IN SOUTHERN CHILE - LONG-TERM INVERTEBRATE ABUNDANCE PATTERNS

Notwithstanding the rapid increase in production levels of cultivated Gracilaria chilensis in Chile, this activity faces several challenges. One of these is related to a drop in the productivity of cultures ove r time, which has been related to the apparent changes in sediment com position and increase of contaminating organisms, such as grazing poly chaetes and mussels, that compete with the farmed seaweed. This study indicates that G. chilensis abundance declines in farmed areas as the period of seaweed cultivation increases. However, the substrate grain size and organic material did not vary significantly in beds planted i n different years. The recruitment of polychaetes did not significantl y increase over time, although their abundance was dependent on the G. chilensis abundance. In contrast to the polychaetes, the abundance of mussels increased over time. Mussel beds could only become establishe d if the G. chilensis farmed area had an algal cover less than 85%. Th is evidence indicates that it is essential to control the recruitment of polychaetes and mussels in order to maintain a high standard of alg al production. However, processes that control their abundances are di fferent, which means that each group will require a different manageme nt strategy. (C) 1997 Elsevier Science B.V.