Effects of Climate Change on Eelgrass Wasting Disease

Maya L Groner1, Colleen A Burge2, Carolyn S Friedman3, Kathy Van Alstyne4, Sandy Wyllie-Echeverria5, Morgan E. Eisenlord6, John Bucci7, Ruth Cox1 and Margaret Turner3, (1)Atlantic Veterinary College, University of Prince Edward Island, Department of Health Management, Charlottetown, PE, Canada, (2)University of Maryland, Baltimore County, Institute of Marine and Environmental Technology, Baltimore, MD, United States, (3)University of Washington, Seattle, WA, (4)Shannon Point Marine Center, Anacortes, WA, United States, (5)University of the Virgin Islands, St Thomas, United States Virgin Islands, (6)Cornell University, Department of Ecology and Evolutionary Biology, NY, United States, (7)University of New Hampshire
Climate change affects the health of marine organisms. Ocean acidification (OA) and rising water temperature can alter species interactions, extend organisms beyond their physiological optima and thus are predicted to increase infectious disease events. When disease impacts ecosystem engineers, community level change is possible. Eelgrass, Zostera marina, are ecosystem engineers providing ecosystem services including carbon sequestration and local mitigation of OA. Eelgrass wasting disease (WD), caused by infection from the opportunist pathogen, Labyrinthula zosterae, can be associated with rapid population declines of Z. marina. We conducted two experiments to determine the influence of OA and increased water temperature (separately) on the presence and severity of the WD. In the first, we grew Z. marina under three C02 conditions, 400, 800, and 1600 ppm, to represent current, 'bad day' and 'future' climate scenarios. After acclimation to these conditions, half the treatments were exposed to L. zosterae. In the high CO2, low pH water, the proportion of diseased Z. marina leaves decreased when compared to leaves in the low CO2, high pH water. In a second experiment, Z. marina adults and seedlings were allowed to acclimate to low (11° C), high (18° C) and fluctuating (between 11 and 18° C) water temperatures and then half these individuals were exposed to L. zosterae. Disease occurred more rapidly and with higher severity in seedlings and at high and fluctuating temperatures. Further analyses will allow us to quantify Labyrinthula load, and production of potential host defenses (total phenols and condensed tannins) among these samples. Our results suggest that host-pathogen relationships for this system will be altered in changing climatic conditions and that further research is needed to understand how climate change influences community resilience and ecosystem system services provided by eelgrass meadows.