Decadal-scale dynamics and response to pulse disturbance in the intertidal rockweed Fucus distichus (Phaeophyceae)

The rockweed Fucus plays an important role in structuring intertidal communities on northern temperate and sub-arctic shores. We performed a 12-year study of Fucus dynamics on a rocky shore in Alaska to (i) describe characteristic dynamics of the Fucus canopy, (ii) test the generality of specific observations that emerged from biological studies following the Exxon Valdez oil spill (EVOS), and (iii) provide a basis for longer-term change analysis in this sub-arctic system. We annually sampled 36 permanent plots within a Fucus community in the Gulf of Alaska to describe canopy dynamics. In two consecutive years, we created small, high-intensity disturbances to test whether synchronous cycles of growth and decline could be detected, as was reported following EVOS. We found only equivocal evidence of synchronous cycles and no long-term signal of intense experimental disturbance. We found no evidence of recruitment inhibition by an established canopy, nor did we find evidence of density-dependent mortality among adults. We did find that Fucus abundance tended to converge on a mode of 50-60% cover, and that annual average deviation from the 12-year mean was 30% or less. We suggest that this system is both dynamic and resilient to natural forcings and intense experimental disturbance events.