Recurrence of the eelgrass wasting disease at the border of New Hampshire and Maine, USA

Eelgrass Zostera marina L. populations in the Great Bay Estuary, on the New Hampshire-Maine border, decreased dramatically between 1981 and 1984. The immediate cause of this decline was not pollution as found recently in other estuaries, but an infection of healthy leaf tissue by a microorganism. The slime mold Labyrinthula, associated with the 1930's eelgrass wasting disease that devasted populations on both sides of the North Atlantic, was isolated from eelgrass tissue, as were other possibly infectious microorganisms. In addition to the decline of eelgrass in the estuary, we have documented the sequence of infection and die-back in mesocosm and laboratory eelgrass cultures that resulted in conditions analogous to those observed in the estuary.