55 



The wasting disease 



The "wasting disease" of 1931-32 greatly depleted eelgrass 

 {Zostera marina L.) populations in the North Atlantic, and most 

 populations did not recover for many decades (den Hartog, 1987) . Other 

 declines were reported in 1890 in the Eastern U.S., and in 1906 in New 

 England (Cottam, 1934). The loss of eelgrass in the 1930's resulted in 

 declines in many animal populations, as well as increased erosion on 

 some beaches (Thayer et al., 1984; Rasmussen, 1977). Because effects of 

 this decline were so profound and longlasting, and because new outbreaks 

 of the disease have been reported (Short et al., 1986), there has been 

 concern about new collapses of eelgrass populations. 



The wasting disease was documented by numerous observers, and its 

 causes and effects have been periodically reassessed (Stevens, 1939; 

 Milne and Milne, 1951; Rasmussen, 1977; den Hartog, 1987) . Before the 

 wasting disease, eelgrass populations were generally described as dense 

 and widespread in temperate waters (den Hartog, 1987) . In the western 

 Atlantic in the summer of 1931, black and brown spots appeared on 

 eelgrass leaves, spread to other leaves and shoots; leaves became 

 necrotic and plants died. The outbreak of the disease continued the 

 following year, and by the end of 1932, the vast majority of eelgrass 

 populations on the east coast of North America disappeared. Events were 

 similar in Europe, but the declines in eelgrass abundance began in 1932, 

 and continued in 1933 (Rasmussen, 1977). Neither eelgrass populations 

 in the Pacific, nor other Zostera spp. endemic in Europe were affected 

 by the disease. 



