Type of Presentation

Oral

Session Title

Kelp and Eelgrass

Description

Understanding the possible reasons for eelgrass decline is especially important considering the importance of seagrasses as essential marine habitat and potential for mitigation of climate impacts. Eelgrass wasting disease of Zostera marina caused by the protist Labyrinthula zosterae presents as necrotic, black-edged lesions on eelgrass leaves and can destroy seagrass beds. This disease devastated Atlantic Z. marina beds in the 1930s and is currently common in the San Juan Archipelago. The prevalence of eelgrass wasting disease in the field varies over space and time, from nearly absent in some sites to almost 100% in other sites during its peak during the summer. Our 11 sites surveyed from 2012-2015 around the San Juan Islands show site-specific patterns of disease prevalence and severity over time but an overall increase in wasting disease prevalence between August 2013 and 2015. A four-month time series of surveys in 2015 shows the annual pattern of wasting disease outbreak between May and August. Furthermore, host demography influenced disease patterns, where the oldest, longest, and most dense beds are the most susceptible to disease. Further surveys coupled with laboratory and mesocosm experiments will investigate what local and regional factors facilitate eelgrass wasting disease in the San Juan Islands and its role in seagrass decline.

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Eelgrass Wasting Disease: a Contributor to Decline in the San Juan Islands?

2016SSEC

Understanding the possible reasons for eelgrass decline is especially important considering the importance of seagrasses as essential marine habitat and potential for mitigation of climate impacts. Eelgrass wasting disease of Zostera marina caused by the protist Labyrinthula zosterae presents as necrotic, black-edged lesions on eelgrass leaves and can destroy seagrass beds. This disease devastated Atlantic Z. marina beds in the 1930s and is currently common in the San Juan Archipelago. The prevalence of eelgrass wasting disease in the field varies over space and time, from nearly absent in some sites to almost 100% in other sites during its peak during the summer. Our 11 sites surveyed from 2012-2015 around the San Juan Islands show site-specific patterns of disease prevalence and severity over time but an overall increase in wasting disease prevalence between August 2013 and 2015. A four-month time series of surveys in 2015 shows the annual pattern of wasting disease outbreak between May and August. Furthermore, host demography influenced disease patterns, where the oldest, longest, and most dense beds are the most susceptible to disease. Further surveys coupled with laboratory and mesocosm experiments will investigate what local and regional factors facilitate eelgrass wasting disease in the San Juan Islands and its role in seagrass decline.