ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Marine Ecosystem Ecology
Volume 12 - 2025 | doi: 10.3389/fmars.2025.1542488
This article is part of the Research TopicTurning with the Tide and Time in the Salish Sea: Change in Estuary and Nearshore Habitats and Species Dependent on ThemView all 13 articles
Deeper eelgrass meadows are refugia from disease and environmental stressors
Provisionally accepted
- 1Cornell University, Ithaca, United States
- 2University of Oregon, Eugene, Oregon, United States
- 3Shannon Point Marine Center, Western Washington University, Anacortes, Washington, United States
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Eelgrass (Zostera marina) creates valuable, biodiverse habitats worldwide, but is at risk from combined environmental stressors and disease. We surveyed paired intertidal and subtidal meadows for seagrass wasting disease in the San Juan Islands, WA, USA in summers 2017-2019 to determine how disease varied with depth, temperature, and salinity. We expected reduced disease in deeper meadows with more stable environmental conditions compared to shallower, intertidal meadows with greater thermal and salinity variation. Leveraging a machine-learning algorithm to detect and quantify disease, we measured high disease levels and large changes in meadow densities, particularly in the warmer 2018 summer. Daily mean in situ and remote-sensed temperatures captured exposure to warming, though in situ temperatures better identified site-specific, seasonal thermal ranges. Subtidal meadows experienced nearly 14°C cooler maximum in situ temperatures compared to intertidal meadows. Disease severity was 2.24 times greater in shallow, intertidal meadows compared to deeper, subtidal meadows over the 3-year study and 1.39 times greater during the 2018 warming. Thus, some subtidal meadows can serve as valuable refugia against environmental and pathogenic stressors. Lower eelgrass densities were also associated with increased severity, suggesting a link between disease and meadow patchiness. Temperature and salinity were also key predictors of higher disease: prevalence and maximum sea surface temperatures covaried, as did severity and salinity range, suggesting these environmental factors may differentially influence seagrass wasting disease risk and progression. Our work highlights the value of both subtidal eelgrass meadows and sites with more stable environmental conditions as refugia from multiple stressors, which should be considered as differential drivers of disease.
Keywords: Salinity, Marine heatwave, Heat stress, resilience, Zostera marina, oceanwarming, Seagrass wasting disease
Received: 09 Dec 2024; Accepted: 10 Sep 2025.
Copyright: © 2025 Graham, Aoki, Rappazzo, Eisenlord and Harvell. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Olivia J. Graham, Cornell University, Ithaca, United States
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