DAO 118:159-168 (2016)  -  DOI: https://doi.org/10.3354/dao02962

Plant characteristics associated with widespread variation in eelgrass wasting disease

Maya L. Groner1,7,*, Colleen A. Burge2, Catherine J. S. Kim3, Erin Rees1, Kathryn L. Van Alstyne4, Sylvia Yang4, Sandy Wyllie-Echeverria5,6, C. Drew Harvell

1Centre for Veterinary and Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada
2Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD 21202, USA
3Department of Ecology & Evolutionary Biology, Cornell University, Ithaca, NY 14850, USA
4Shannon Point Marine Center, Western Washington University, Anacortes, WA 98221, USA
5Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA
6Center for Marine and Environmental Studies, University of the Virgin Islands, St. Thomas, VI, USA
7Present address: Dept. of Fisheries, Virginia Institute of Marine Science, 1208 Greate Road, Gloucester Point, VA 23062, USA
*Corresponding author:

ABSTRACT: Seagrasses are ecosystem engineers of essential marine habitat. Their populations are rapidly declining worldwide. One potential cause of seagrass population declines is wasting disease, which is caused by opportunistic pathogens in the genus Labyrinthula. While infection with these pathogens is common in seagrasses, theory suggests that disease only occurs when environmental stressors cause immunosuppression of the host. Recent evidence suggests that host factors may also contribute to disease caused by opportunistic pathogens. In order to quantify patterns of disease, identify risk factors, and investigate responses to infection, we surveyed shoot density, shoot length, epiphyte load, production of plant defenses (phenols), and wasting disease prevalence in eelgrass Zostera marina across 11 sites in the central Salish Sea (Washington state, USA), a region where both wasting disease and eelgrass declines have been documented. Wasting disease was diagnosed by the presence of necrotic lesions, and Labyrinthula cells were identified with histology. Disease prevalence among sites varied from 6 to 79%. The probability of a shoot being diseased was higher in longer shoots, in patches of higher shoot density, and in shoots with higher levels of biofouling from epiphytes. Phenolic concentration was higher in diseased leaves. We hypothesize that this results from the induction of phenols during infection. Additional research is needed to evaluate whether phenols are an adaptive defense against Labyrinthula infection. The high site-level variation in disease prevalence emphasizes the potential for wasting disease to be causing some of the observed decline in eelgrass beds.


KEY WORDS: Opportunistic pathogens · Seagrass declines · Phenols · Plant defenses · Labyrinthula · Coastal ecosystems · Restoration · Zostera marina


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Cite this article as: Groner ML, Burge CA, Kim CJS, Rees E and others (2016) Plant characteristics associated with widespread variation in eelgrass wasting disease. Dis Aquat Org 118:159-168. https://doi.org/10.3354/dao02962

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