Marine debris in central California : quantifying type and abundance of beach litter in Monterey Bay, CA
Thesis (M.S.) Division of Science and Environmental Policy
The Monterey Bay on the central coast of California lies within a protected marine sanctuary where recreation, tourism, and marine species coexist. Marine debris washing ashore poses a human health risk as well as contributing to economic losses and ecological harm. Central Californiaâ€™s coastal managers require reliable scientific information on debris abundance, distribution, and type to help ameliorate this threat. To help address potentially harmful beach debris, I created a survey method which allows for trained volunteers to quantify the types and abundance of beach litter. This method was put into effect at twelve beaches within the Monterey Bay in California. Employing trained volunteers increased efficiency and allowed the simultaneous sampling of twelve beaches monthly over one year. We conducted surveys at low tide from July 2009 through June 2010. Surveyed beaches included: Santa Cruz Main, Seabright, Live Oak, Capitola, New Brighton, Sea Cliff, Manresa, Sunset, Zmudowski, Marina, Seaside, and Del Monte. At each survey site volunteers randomly placed quadrats to facilitate data collection along two parallel 50m transects. We found litter on all beaches surveyed. A total of 5966 individual pieces of litter were collected during this study. Styrofoam made up 41% of the total amount of litter, making it the most numerically abundant item found. Unexpected items included plastic pellets (9% of total plastics) and fertilizer capsules (1% of total litter). I analysed spatial and temporal relationships between litter abundance using mixed effect modeling, and best fit was ascertained using Akaikeâ€™s Information Criterion (AIC). The results of this study demonstrated that beach location, while influential, had less of an effect on litter abundance than month. The temporal and spatial variance in litter type and abundance suggest a relationship to physical and environmental factors, such as proximity to agricultural fields and surface current movement within the bay. The results of this study can be directly applicable to developing monitoring programs for beach debris and could be adopted by coastal cities to monitor their own environmental and political successes in abating beach litter. In addition, this study has strengthened relationships with agencies, municipalities, educators and community organizations, as these relationships are essential for decision-making, scientific monitoring, and community outreach.