Beach wrack ecology at Crystal Cove State Park

Crystal Cove State Park (CCSP) is one of few beaches in southern California that does not remove beach wrack. Beach wrack, marine organic material deposited from other ecosystems, includes algae, seagrass, marine phytoplankton, and carrion and is the key nutrient subsidy to this highly dynamic habitat. Many invasive brown algae species from the genus Sargassum have in some locations outcompeted and replaced native kelp offshore, potentially affecting wrack communities. Anthropogenic impacts such as oil spills, trash pollution and mechanical grooming also disrupt shoreline communities. This paper examines spatiotemporal patterns of wrack deposition, Sargassum presence, avian biodiversity and wrack pollutants at CCSP. Study design included randomized belt transects extending from the terrestrial vegetation line to the swash zone. Wrack piles were assessed for abundance, species composition, dominance, volume, weight, desiccation and pollutant presence from November 2021 to April 2022. Wrack abundance varied spatially and temporally, however, Sargassum abundance indicated no significant trends. Seagrass abundance varied spatially but not temporally. Five minute timed bird surveys were conducted at each survey location to examine patterns in avian presence. Initiating a long-term wrack monitoring program at CCSP will position the park to guide long-term management decisions regarding invasive species management and wrack conservation.Our study site was divided as follows: Treasure Cove, Pelican Point, Scotchman's Cove, Reef Point, and Moro. Each subzone was surveyed at regular intervals once per month. We created five random, five-meter long belts running down towards the water from a main perpendicular 100m primary transect. For each pile within the belts, abundance data was collected by measuring length/width, noting trash and/or oil, and determining which species are present and most abundant. Three representative piles were then split up by species and measured for weight, volume, and desiccation. Using bird identification guides, bird surveys were also conducted to monitor what species and how many were utilizing wrack. Bird abundance and diversity was documented by guild. Data was analyzed utilizing two software programs: RStudio and ArcGIS. Maps were created using GPS data from location collection instruments and data collected from surveys