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stepwise colonization, hydrographic and geographic isolation, and 

 heterogeneity of the substrate (above and Costa, 1988) . 



Causes for recent declines 



Superimposed on the long-term pattern of gradual recovery and 

 continued expansion after the disease are local declines that were the 

 result of other natural or anthropogenic disturbances. Eelgrass 

 populations generally recovered from natural disturbances within ten 

 years. For example, severe storms in 1938, 1944, and 1954 destroyed 

 eelgrass in some exposed or shallow areas in Buzzards Bay and Cape Cod 

 (above and Costa, 1988). In less exposed areas, eelgrass recolonization 

 was only slowed by these disturbances. Ice scour often removes eelgrass 

 in shallow areas, as was evident along the shallow margins of beds in 

 East Bay, Fairhaven and along Great Neck, Wareham during severe winters 

 in 1977-1979. In shallow Bays like Apponagansett Bay, So. Dartmouth and 

 the Westport River basin, ice accumulation coincide with major 

 fluctuations in eelgrass abundance. 



New losses due to human perturbation have been longer lasting. 

 The disappearance of eelgrass in the north end of the Westport Rivers, 

 Apponagansett Bay, Dartmouth; Little Bay, Fairhaven; Wareham River, 

 parts of Sippican Harbor, Marion; Clarks Cove, Dartmouth; Waquoit Bay, 

 Falmouth (on Vineyard Sound) , and other coastal lagoons on Cape Cod (in 

 prep.) appears to be due to decline in water transparency from nutrient 

 loading because these areas have conspicuous macroalgal growth, poor 

 water transparency, abundant periphyton, prominent gradients of maximum 

 eelgrass growth and related declines in water quality such as shellfish 



