Thesis Defense: Sarah Donaher

The Master’s Thesis Defense of Sarah Donaher will be presented by the University of North Carolina at Chapel Hill Department of Marine Sciences and Institute of Marine Sciences. This event will be held on Wednesday, March 18th at 9:00 am. The main location of this event will be in room 222 of UNC’s Institute of Marine Sciences in Morehead City, NC. The defense will be streamed live to conference room 3204 on the 3rd floor of Murray Hall on UNC main-campus in Chapel Hill, NC and online via Zoom (Use Zoom Meeting ID: 252 726 6841).

Title: Disturbance regime modifies species interactions in a North Carolina seagrass bed

Abstract: Rapid global degradation of seagrass habitats can be attributed to anthropogenic activities associated with coastal development, aquaculture, and recreational surface water use. Despite the dedication of considerable effort by scientists and practitioners in researching how to restore these highly productive habitats, restoration project success rates have remained low. Therefore, it is critical to develop and test novel approaches which promote seagrass bed resilience to human-caused disturbances. We hypothesized that the addition of a facultative mutualist, the hard-shell clam, could enhance seagrass recovery after a disturbance by mitigating environmental stress and enhancing sediment nutrient content via biodeposition. We designed two experiments to examine the independent and interacting effects of a physical disturbance and hard-shell clam presence in mixed community seagrass beds in North Carolina. Increasing the density of clams in seagrass beds exposed to a physical disturbance increased seagrass summer productivity (shoot growth rates) and autumn shoot densities. In contrast, increasing clam densities in non-disturbed seagrass beds reduced seagrass growth rates and shoot densities. These results suggest that environmental conditions may mediate the effects of clams on seagrass; occasional perturbations in the system may alter the effects of clams on seagrass from negative to positive. Clam enhancement of autumn shoot densities were most prominent after Hurricane Dorian, suggesting that clams may enhance seagrass resilience to repeated disturbances. Understanding when and how to utilize positive, interspecific interactions in coastal restoration could improve restoration success rates.