Eelgrass (Zostera marina) is a marine angiosperm (flowering plant) of great importance in the Northern Hemisphere. It plays important roles in sediment deposition, substrate stabilization, as substrate for epiphytic algae and microinvertebrates, and as nursery grounds for many species of economically important marine vertebrates and macroinvertebrates. Historically, it was at one time the principle material for the Dutch dikes and has been used as stuffing for mattresses and cushions. (Haynes 2000) Felger and Moser (1973) reported on the use of Eelgrass seeds as food by the Seri Indians, traditional hunters and gatherers of Sonora, Mexico. According to the authors, this is the only known case of a grain from the sea being used as a human food source.
In the 1930s, Zostera marina suffered dramatic die-offs on the Atlantic coasts of North America and Europe. The plants would develop large brown spots on the leaves and rhizomes and slowly die. This "wasting disease" eventually led to the disappearance of most of the eelgrass in the North Atlantic, along with much of the fauna that depended on it (Short et al. 1987; Haynes 2000). Over the decades, Eelgrass gradually re-established itself in many (though not all) of the areas it had previously occupied. The cause of the widespread wasting disease has been established to be a fungus-like protist, Labyrinthula zosterae, which dramatically reduces photosynthetic capability (Ralph and Short 2002). Wasting disease continues to affect Eelgrass meadows in North America and Europe with variable degrees of loss, though none to date as catastrophic as the epidemic of the 1930s (Short et al. 1987; Ralph and Short 2002).