Meeting Abstract

P1-29    The role of eutrophication on disease in the seagrass Zostera marina Lighthouse, E*; Fink, R; Brothers, CJ; Walla Walla University; Walla Walla University; Walla Walla University cecilia.brothers@wallawalla.edu

Seagrass wasting disease (SGWD) is caused by protist pathogens in the genus Labyrinthula. It causes cellular degradation and the development of necrotic lesions in infected plants, eventually resulting in plant death. Eutrophication in seagrass meadows from industrial and residential runoff may contribute to disease severity. During the summers of 2019 and 2020, we surveyed seven seagrass meadows in the Salish Sea, WA. We measured nutrient levels (nitrate and phosphate) at each site and analyzed images of seagrass blades for occurrence (percent of samples infected) and disease severity (area of blades covered in lesions) using ImageJ. The occurrence and severity of SGWD varied significantly across collection sites. Disease severity was highest at Padilla Bay (9% in 2019 and 10% in 2020), which is the site that also possessed the highest levels of nutrients. In the laboratory, plants from Padilla Bay were grown under low and high nutrient conditions. At the end of five weeks, we analyzed disease severity, plant height, and plant weight as proxies for seagrass health between the two treatments. Seagrass plants grown in high nutrients displayed more disease and grew significantly less than plants from low nutrients. These combined results from the field and the laboratory suggest that eutrophic conditions contribute to higher prevalence of SGWD and negative impacts on growth, which both lead to a decline in seagrass health.