65 



this model demonstrated that the colonization of bare areas by eelgrass 

 greatly depends on colonization by new seedlings. To a lesser degree, 

 rates of colonization depend on vegetative growth rates and levels of 

 disturbance. Disturbance intensity, however, does affect the % cover of 

 an eelgrass bed at peak abundance. Hence, an eelgrass bed cover in a 

 high energy, wave swept shore, may never cover more than 50% of the 

 available substrate due to winter storms and wave scour. 



Methods 



Photograph analysis 



In Massachusetts, parts of the coastline have been repeatedly 

 photographed since 1938, and these photographs were obtained from 

 various private and governmental agencies (Appendix I) . Most of these 

 photographs were taken between late spring and fall when eelgrass is 

 densest, but photographs taken during other periods were are also 

 informative, particularly when mapping perennial eelgrass populations. 

 Only one set of photographs taken prior to the wasting disease was found 

 (Sippican Harbor, Marion, taken June of 1930). 



Photographs were analyzed and interpreted as described in chapter 

 1. As described earlier, there are four types of vegetation that 

 resemble eelgrass beds, but can usually be distinguished on photographs: 

 drift algae, salt marsh peat reefs, algal covered rock fields, and shell 

 and gravel areas where the green alga Codium may be abundant. Codium, 

 however, is a recent introduction and was not abundant in Buzzards Bay 

 prior to the late 1960's (Carlton and Scanlon, 1985). Similarly, drift 



