17 



Several features are apparent on aerial photographs that deserve 

 discussion because they affect estimates of eelgrass cover. On the 

 outer coast, eelgrass beds appear as dark patches on a light background 

 (sand). In some exposed areas, algae covered rock and cobble dominate 

 the bottom, as well. Algal diversity is high in this region, but Fucus 

 and Ascophyllum are most common in the intertidal, and Chondrus, 

 Ceramium, Codium and Sargassum in the subtidal. In addition, kelps are 

 abundant in some deep, rocky areas with clear water, such as around the 

 Elizabeth Islands and off Westport and Dartmouth. Most of these algae- 

 covered rock and cobble fields can be distinguished from eelgrass beds 

 by their characteristic "texture". 



In protected areas with mud bottoms, contrast between eelgrass and 

 its background is reduced, but eelgrass can usually be discerned as a 

 dark patch on a slightly lighter bottom. In some bays, benthic drift 

 algae form large mats which can be mistaken for eelgrass beds, but 

 eelgrass growing in these areas appear as a slightly lighter patches on 

 a dark background. 



In moderate energy environments, with shell and gravel bottoms, 

 the green alga Codium may be abundant within eelgrass beds. Codium can 

 also dominate the bottom below depths of eelgrass growth, making it 

 difficult to estimate eelgrass bed dimensions and percent cover of 

 eelgrass in some areas. Even though Codium is common, it rarely covers 

 the bottom in as large an area, or as densely as eelgrass beds. 



Salt marsh peat reefs, remnants of salt marshes covered by 

 migrating barrier beaches then re-exposed after sea-level rises, are 

 common in some areas, usually near existing marshes. These reefs have a 



