Sara Briley

Sara Briley

Former Graduate Student

M.S. Biology 2015

Response of Zostera marina to an adjacent Olympia oyster restoration project in southern CA

Sara’s master’s research evaluated the larger ecosystem impacts of native Olympia oyster restoration on a co-occurring species of eelgrass, Zostera marina. Restoration of the native Olympia oyster, Ostrea lurida, is gaining steam in southern California, however, its impact on another species of restoration concern, eelgrass Z. marina, is unclear. Understanding the impact of oyster restoration on eelgrass is vital as oyster restoration efforts expand and overlap with eelgrass restoration efforts in southern California. Extremely low recent population sizes of O. lurida have prevented study of the interaction of these two species, but an Olympia oyster restoration project built shoreward of an existing eelgrass bed in Alamitos Bay, Long Beach, CA offered a unique opportunity to examine this relationship. Sara monitored the response in eelgrass adjacent to the constructed restoration project compared to two nearby reference eelgrass beds not impacted by oyster restoration.

Though she observed some minor short-term effects of the constructed oyster bed, she did not detect a conspicuous impact on the adjacent eelgrass bed. She found a minor impact on light, which was significantly lower each day in the impact site than in the control site for 3 months following construction. She observed leaf morphological variations between the sites as the eelgrass in the control site became denser, with shorter and narrower leaves, while the impact bed maintained a more consistent density and mean leaf size. Declines in below-ground biomass after construction of the oyster bed were observed in the impact site only, but did not translate into above-ground biomass loss. Overall, the changes observed were not outside the wide range of natural variation expected in this system, nor were they detrimental. These findings support the potential coexistence of a constructed Olympia oyster bed and adjacent eelgrass, which is relevant to the design of future restoration efforts for both species.

Sara is the Department and School of Natural Sciences and Mathematics nominee for the 2015 Giles T. Brown Outstanding Thesis Award. She is currently the Restoration Coordinator for OC Coastkeeper and is overseeing southern California’s first Living Shorelines Project. You can find out more information about her current work here: