Wasting Disease

In the early 1930s, a species of seagrass common to temperate North America, eelgrass (Zostera marina), disappeared from a large portion of its range. The die-off event is commonly attributed to the "wasting disease." Within two years, 90 percent of all eelgrass populations in the North Atlantic (from Canada to North Carolina) had disappeared (Rasmussen 1977, review by Thayer et al. 1984). The disease similarly ravished coastal Europe’s eelgrass populations.

Close-up view of a lesion caused by Labyrinthula
Close-up view of a lesion caused by Labyrinthula
Courtesy: Florida Marine Research Institute

The exact cause of the "wasting disease" is unknown, but there is evidence of historical seagrass die-offs (Rasmussen 1977). Originally, the causative agent was hypothesized to be a marine slime mold (Labyrinthula). Labyrinthula invades weak or stressed leaves, causing brown lesions that reduce the ability of the plant to photosynthesize and may eventually lead to death. However, the fungus is known to be present in many unaffected seagrass meadows (Rasmussen 1977). The confusion has prompted the exploration of many potential causes, including the possibility that warmer ocean temperatures prompt and/or contribute to the massive die-offs (Rasmussen 1977). Regardless of the cause, the "wasting disease" outbreak of the 1930s brought global attention to the importance and value of seagrass, as economically valuable crustaceans, finfish and shellfish populations declined, migratory waterfowl declined, and beaches and shorelines significantly eroded (Rasmussen 1977, review by Thayer et. al 1984).

Rasmussen, E. 1977. "The Wasting Disease of Eelgrass (Zostera marina) and Its Effects on Environmental Factors and Fauna." In Seagrass Ecosystems: A Scientific Perspective, edited by C.P. McRoy and C. Helfferich. Dekker, New York.

Thayer, G.W., W.J. Kenworthy, and M.S. Fonseca. 1984. The Ecology of Eelgrass Meadows of the Atlantic Coast: A Community Profile. U.S. Fish and Wildlife Service Division of Biological Services. FWS/OBS-84/02.

Source: NOAA Coastal Services Center. Guide to the Seagrasses of the United States of America (Including U.S. Territories in the Caribbean). Available on U.S. National Oceanic and Atmospheric Administration. Coastal Services Center. Submerged Aquatic Vegetation: Data Development and Applied Uses. (CD-ROM). (NOAA/CSC/20116-CD). Charleston, SC. 2001.