Research Technical Report

Shipwrecks on Sanctuary Shores: Disturbance and Recovery Along a Rocky Intertidal Exposure Gradient

McConnico, L.A. and M.S. Foster (2005)

Unpublished Final Report, 30 pp.

ABSTRACT

Recovery rates and processes were assessed along a rocky intertidal height gradient impacted by a shipwreck in Monterey Bay, California. This anthropogenic disturbance, fractured and scoured rock surfaces, was used to determine if recovery rates varied inversely with tidal height due to reduced abiotic stress from reduced exposure to air. Disturbed and control (undisturbed) plots were established in a mid/high intertidal red algal dominated by Endocladia muricata and Mastocarpus papillatus, mid intertidal mussel (Mytilus californianus), and low intertidal surfgrass (Phyllospadix spp.) assemblage. Percent cover of sessile organisms in 0.25 x 0.25-m plots in each of the assemblages was assessed between 1996-1998 and 2001-2002. Recovery rate was measured as the temporal change in the difference in similarity between disturbed and control plots. Ephemeral seaweeds initially colonized all disturbed plots, but were replaced by later successional species within 2-12 months. Contrary to expectation, recovery rate did not vary inversely with tidal height: it was greatest in the high intertidal red algal assemblage, followed by the surfgrass and Mytilus assemblages. The patterns of recovery suggest that assemblages characterized by a few dominant species that recruit rapidly and grow quickly (the red algal assemblage) will recover faster than those dominated by species with variable, episodic recruitment (mussel beds), or those that have limited success with sexual versus vegetative propagation (surfgrass). Life history features may be more important predictors of recovery than stress.