Award: OCE-1829921

Seagrass meadows are essential habitats that support marine biodiversity and coastal communities. This project developed new monitoring technologies and has showed that warming temperatures stress seagrass meadows on a continental scale from San Diego to Alaska and can facilitate seagrass wasting disease. Disease outbreaks contribute to large-scale diebacks of seagrass meadows, including eelgrass (Zostera marina). Large-scale surveys (San Diego to Alaska) were made possible for the first time by the Eelgrass Lesion Image Segmentation Application (EeLISA), an artificial intelligence (AI) system that quantifies eelgrass wasting disease 5000× faster and with comparable accuracy to a human expert. EeLISA allowed us to detect climate-sensitive changes in health of seagrass meadows and won an Innovative Applications of Artificial Intelligence Award from Association for the Advancement of Artificial Intelligence. We assessed wasting disease sensitivity to warming temperatures across a 3500 km study range by combining long-term satellite remote sensing of ocean temperature with field surveys from 32 meadows along the Pacific coast of North America from 2019-2022. IN 2019, between 11% and 99% of plants were infected in individual meadows, with up to 35% of plant tissue damaged. Disease prevalence was three times higher in locations with warm temperature anomalies in summer, indicating that the risk of wasting disease increases with climate warming. High-resolution drone imagery sowed seagrass declines between 2019 and 2021. In June 2021, the study region experienced an unprecedented heating event (the 2021 Pacific Northwest Heat Dome). Unmanned aerial vehicle (UAV) imagery collected 2 years before and immediately following this event showed the dramatic loss of seagrass density and coverage for monitoring sites in Washington State. Our surveys from 2019 to 2021, combined with our historical data from 2013 show that seagrass meadows in the San Juan Islands, WA, USA, have declined over the last decade. Shoot densities, measured along permanent monitoring transects, fell over 90% from 2013 to 2021, while wasting disease prevalence (percent infected plants) remained persistently above 40% since the 2016 Northeast Pacific heat wave. Since 2019 as part of this grant research, we synchronized UAV drone surveys with midsummer in situ sampling. At all locations from San Diego to Alaska The UAV imagery greatly expands the scope of the data, extending beyond the monitoring transects to confirm large-scale loss of seagrass at key locations. At a finer spatial scale, we conducted field surveys to determine the impact of wasting disease on eelgrass growth and belowground sucrose in situ. Our analyses clearly demonstrated that wasting disease compromised eelgrass growth and was associated with reduced belowground sucrose, which is important in helping plants survive harsh winter conditions. This provides further evidence of the negative impacts of wasting disease on eelgrass health, and potentially, long-term survival. This loss of habitat will have cascading ecological consequences, including reduced abundance of resident animals, such as crabs, fish and snails. With worsening wasting disease outbreaks under climate change, these new approaches combining drone imaging, in situ surveys, molecular diagnostics and artificial intelligence are needed to understand seagrass meadow dynamics across space and time. This work has the potential to inform future eelgrass conservation and management efforts for the sustainability of these valuable marine habitats. This project contributed to development of human resources through the training of three PhD students, five undergraduate interns and three postdoctoral fellows. Results from the project were shared widely at talks given at over five national/international conferences, active social media reporting and popular articles in the New York Times. Last Modified: 12/20/2022 Submitted by: C. Drew Harvell