Reprint Series No. 31

NON-LINEAR RESPONSE OF THE BROWN SEAWEED FUCUS GARDNERI TO THE INTENSITY OF DISTURBANCE REVEALS A DENSITY THRESHOLD

Markus G. Speidel

 

November 1999

Bibliographic Citation
Speidel, Marcus G. 1999. Non-linear response of the brown seaweed Fucus gardneri to the intensity of disturbance reveals a density threshold. Report to the Washington State Department of Ecology (Publication No 00-06-009), Padilla Bay National Estuarine Research Reserve, Mount Vernon, Washington. 44 pp. Padilla Bay National Estuarine Research Reserve Reprint Series No. 31.

Abstract
The recovery of the brown seaweed Fucus gardneri to controlled pulse disturbances of different intensities were studied on a rocky shore in Padilla Bay, Washington, USA. The percent ground cover of this dominant alga was reduced by twenty-percent increments to simulate different levels of disturbance and examine the linearity of subsequent recovery. Abundance of invertebrate grazers and ephemeral algae were monitored as well to examine indirect effects on the community. The recovery of F. gardneri cover one year after the disturbance was markedly non-linear, with a threshold to disturbance observed between plots reduced to 20% and 0% Fucus cover. The abundance of invertebrate grazers and ephemeral algae did not vary significantly with the intensity of disturbance. These results add to the corpus of work demonstrating that ecological responses to disturbance are often non-linear, and suggest that manual removal of Fucus may be an effective method of cleaning oil from rocky shores following a spill without significantly impairing biological recovery.