September 19, 2016

Island Biogeography

Alumni Michaela Miller

Trends in Ventura County marine debris: 30 years of change on mainland and Channel Island beaches

The persistence of plastics in marine ecosystems, and the outright physical hazards marine debris poses to wildlife has become an issue of global concern. The Santa Barbara Channel is home to a number of important marine and coastal ecosystems, as well as a variety of factors fostering marine debris accumulation. To examine the spatial variation of marine debris across the Santa Barbara Channel we quantified marine debris on Santa Rosa Island and Santa Cruz Island beaches and mainland beaches in Ventura County. To examine the temporal variation of marine debris on Santa Rosa Island we compared our surveys to historical surveys performed from 1989-1994 (Cole 1998). Debris from surveyed beaches was cataloged, weighed, and measured to compare seasonal variation and overall differences in island and mainland marine debris abundance, density, and composition. Derelict fishing gear accounted for a higher proportion of marine debris on island beaches compared to mainland beaches, and marine debris items on island beaches were significantly heavier compared to the mainland beaches. There has been a significant increase in the amount of derelict fishing gear found over the past 27 years on Santa Rosa Island, which mirrors changes in the California lobster fishery. The majority of debris on mainland beaches was comprised of smaller plastic fragments and single use plastic items, and debris accumulation rates varied by season and location. Microplastics (<5mm) were also found in the sand of all surveyed island and mainland beaches. This study highlights the importance of consistent marine debris monitoring, as local changes in policy, fisheries, and consumer culture are reflected in the marine debris found on the mainland and especially the uninhabited Channel Islands. Monitoring marine debris can provide insight on anthropogenic impact, and is a useful mechanism in monitoring the health of coastal and marine ecosystems.