Research Technical Report

Recovery of Rocky Intertidal Assemblages Following the Wreck and Salvage of the F/V Trinity

Walder, R.K., M.S. Foster, and A. DeVogelaere (1998)

Sanctuary Currents Symposium, March 1998

ABSTRACT

In April 1996, the fishing vessel Trinity ran aground on a rocky shore of the Monterey Peninsula. Subsequent salvage operations included rolling the vessel to a shore-based crane and using tractor tires as cushions to minimize habitat crushing. This event resulted in 108 m2 of physical damage from the grounding, 287 m2 of possible diesel fuel impacts, and 143 m2 of physical damage from the salvage operation. Biological recovery is being investigated quantitatively within three assemblages: low intertidal surf grass, mid intertidal mussel and mid/high intertidal red algae. Moreover, recovery is being qualitatively assessed in a unique rubble bed and sand pits created by the vessel and tractor tires during overnight stoppage of the salvage operation. Finally, a potential rocky shore restoration technique is being developed for future large scale disturbances by transplanting boulders with intact biological assemblages. As of December of 1997 recovery within areas has occurred slowly. Overall, disturbed plots in the mussel and red algal assemblages contained species indicative of the intact, adjacent assemblages. However, their percent cover in both cases was relatively low. Within the surf grass assemblage, only one species indicative of that assemblage, Corallina vancouveriensis, has colonized the disturbed areas. In addition, 89% of transplanted boulders persisted with their associated plants, providing habitat and a potential source of spores. Comparisons between impacted and adjacent control areas suggest that spilled diesel fuel had no impacts. Recovery of this rocky shore is clearly a multi-year process and different for each assemblage. The restoration techniques can potentially enhance natural recovery. Salvage efforts would be less destructive by minimizing operation time.