Seagrasses are found in dense meadows along the coastline and provide essential ecological and economic benefits. However, seagrass meadows are also one of the most threatened ecosystems on the planet, and outbreaks of seagrass wasting disease (SGWD) may be contributing to the decline of seagrass meadows in the Pacific Northwest. SGWD is caused by the marine protist Labyrinthula spp. which produces dark necrotic lesions, reduced photosynthetic activity, and eventual plant mortality. The pathogen is abundant in the marine environment, but anthropogenic impacts such as nutrient pollution may make seagrass meadows more vulnerable to Labyrinthula spp. infection. We surveyed seven intertidal seagrass meadows (Zostera marina) in the Salish Sea during summer 2019. At each site, we quantified disease incidence (% of plants displaying necrotic lesions) and severity (% of leaf covered in lesions) from photographs using Image J. Both the incidence (2–96%) and severity (0–9%) of disease was significantly different across sites. The incidence and severity of disease was highest at Padilla Bay, WA which also possessed the highest seawater nitrate levels. In the laboratory, plants were held under low and high levels of nutrient pollution (nitrate and phosphate) for 30 days before being inoculated with Labyrinthula spp. and the progression of SGWD was observed. Seagrass exposed to high nutrient levels displayed significantly more SGWD than seagrass exposed to low nutrient levels, suggesting eutrophication may be one factor influencing the severity of SGWD.