Seagrass ecosystems provide important services to people in coastal regions worldwide, fostering vigorous production, habitat for fisheries, processing of nutrient runoff, carbon storage, and erosion control. The world?s most widespread seagrass species, eelgrass (Zostera marina) forms extensive meadow on both sides of the north Atlantic and north Pacific oceans. But like many marine habitat-forming species, eelgrass is vulnerable to disease epidemics, which can have catastrophic ecosystem impacts but are poorly understood. This collaborative research project engaged partners from 11 institutions and a broad range of expertise to evaluate how environment and interacting biological communities mediate the prevalence and severity of eelgrass wasting disease, caused by the pathogenic protist Labyrinthula zosterae, along the west coast of North America from San Diego to Alaska. The multidisciplinary team employed remote sensing, field surveys, and experiments to tease apart the effects of recent heat waves, interactions with grazing animals, and microbes on eelgrass wasting disease infections across this continental-scale range. All of the teams included early-career scientists, who benefited from new field research experiences and rich opportunities for shared learning, immersion in team science, and building professional and peer networks. 

This project was unprecedented in marine ecology in its combination of geographic scale, standardized sampling, and integration of components ranging from molecular to seascape scales, all focused on the holistic ecology of disease affecting a foundation species of major importance in coastal ecosystems. The team’s research documented for the first time the important, interacting effects of climate and biodiversity in mediating wasting disease dynamics. Field studies showed that warming water temperatures stressed eelgrass across large regional scales from San Diego to Alaska, facilitating seagrass wasting disease, which in some areas contributed to large-scale diebacks of eelgrass meadows.

Moreover, we identified two species interactions that modify the effect of temperature on wasting disease.  First,  several bacterial taxa whose presence and abundance on uninfected tissue are predictive of wasting disease prevalence across the geographic range including Cellvibrionaceae, degraders of plant cellulose, which were also enriched in lesions and adjacent green tissue relative to nonlesioned leaves. These bacteria may play important roles in disease progression by degrading host tissues or overwhelming plant immune responses. Interactions between temperature stress and plant microbiome likely play a key role in understanding the plant stress response. Additionally, the numerous small crustaceans and snails that live among eelgrass leaves appear to modify eelgrass host-disease interactions through their grazing activities, with some grazer species increasing and some species decreasing disease prevalence. Because temperature can accelerate grazing rates, this provides an additional novel pathway by which temperature can indirectly influence disease impact.

The research combined two new innovations to revolutionize the scale and speed of surveillance for eelgrass wasting disease, namely (1) Unoccupied Aerial Vehicles (UAVs, or drones), used by the university of Central Florida team for high-resolution mapping (< 0.05 m) that enables unprecedented and inexpensive fine-scale image analysis of individual seagrass leaves over large areas, and (2), an artificial intelligence system, the Eelgrass Lesion Image Segmentation Application (EeLISA), developed by the Cornell team, that quantifies eelgrass wasting disease 5000 times faster and with comparable accuracy to a human expert. Of several important articles published or in press from this work, a paper led by Postdoc Bo Yang (Geophysical Research Letters) describes the ground-breaking result of combining these twin innovations: eelgrass Green Leaf Area Index detected with drone imagery is a strong predictor of wasting disease prevalence measured on eelgrass plants sampled in the water, across three regions: Alaska, British Columbia, and California. Together, these innovations offer substantial promise for application in rapid assessment of eelgrass disease for management.

Last Modified: 12/28/2023
Modified by: John J Stachowicz