Succession and seasonal variation in the development of subtidal macrobenthic soft-bottom communities off northern Chile

Community succession is an important process in modulating the structure of benthic soft-bottom communities. A field experiment was conducted aiming (1) to describe the successional development in a subtidal soft-bottom community over a two-year period, (2) to estimate the time necessary for the developing community to resemble the surrounding natural community, and (3) to evaluate the effect of seasonal onset on the colonization over a one-year period of development. Containers filled with fine sediment without any previous biological conditioning were installed in subtidal soft bottoms off Playa Colorado, Bahía Antofagasta, Chile (Humboldt Current System). The experiment was initiated in June 2006. For 24 months three replicate containers together with 4 reference samples from the surrounding natural community were sampled every three months. Succession was detected but did not show a sequential replacement from early to late colonizers, thus did not follow distinguishable seral stages. These results support the tolerance succession model, which states that species dominating later successional stages colonize at the same time as species mainly associated with initial successional stages. Resemblance to the reference community was first recorded after eighteen months. In order to test for seasonal effects of colonization, three containers were installed in each of the four seasons, and the community was allowed to develop for a one-year period. Seasonality had no evident effect, as all establishing communities converged to a similar structure after one year, regardless of the season, when the containers had been installed. This study highlights the strong resilience of northern Chilean sublittoral soft-bottom communities to environmental variations during the cold conditions of the El Niño Southern Oscillation.