The Olympia Oyster, Ostrea lurida, is the only oyster species native to the West coast of North America. O. lurida is a foundational species providing ecosystem services including shoreline stabilization, water filtration, fish habitat, and food for shoreline birds. Populations once ranged from British Columbia to Baja California, but have declined dramatically due to development and pollution. Previous studies conducted surveys and mapped oysters along the California Coast, finding many in estuaries. The Carpinteria Salt Marsh, a University of California Natural Reserve, was once home to one of the largest natural populations of O. lurida in Southern California. Many oysters were found in 2017 but the Thomas Fire and Montecito Mudslides in early 2018 covered the marsh with mud and debris, killing most of the oysters and destroying their habitat. This study explores the impact of the 2018 debris flow on O. lurida populations in Carpinteria Salt Marsh, and the restoration bottlenecks limiting their recovery. In order to investigate this, surveys and recruitment experiments were done on the oyster population.
Results/Conclusions
Based on surveys performed from 2017 to 2020, the O. lurida populations in the salt marsh have decreased by 90% post debris flow. A map on ArcGIS was made from the survey data, and represents how the status O. lurida populations have changed through time. From recruitment experiments, which involved natural substrate and artificial substrate for larvae settlement, the oyster larvae preferred the artifical substrate. These findings can begin to inform mangement and conservation to attempt to increase oyster populations before they become locally extinct in Carpinteria. By using the survey map and locations of suitable substrate restoration work can begin where both exist and expand the area O. lurida occupies over time. The decline of O. lurida has been a pressing issue within the fields of oyster restoration and ecology. Still, researchers have not investigated the effects natural disasters have on this decline. The impact of natural disasters on ecosystems becomes increasingly important as disasters become more frequent due to climate change.