Abstract

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 over time, which has been related to the apparent changes in sediment composition and increase of contaminating organisms, such as grazing polychaetes 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 in different years. The recruitment of polychaetes did not significantly 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 established if the G. chilensis farmed area had an algal cover less than 85%. This evidence indicates that it is essential to control the recruitment of polychaetes and mussels in order to maintain a high standard of algal production. However, processes that control their abundances are different, which means that each group will require a different management strategy.