33 



Chapter 3 



Evidence for long-term changes in eelgrass (Zostera marina L.) abundance 



in Massachusetts in sediment cores 



Introduction 



Analysis of core sections from coastal marine depositional 

 environments shows great promise for assessing the impact of 

 anthropogenic and natural disturbances that have taken place during 

 recent centuries. For example, in Chesapeake Bay, sediment cores were 

 used to document increases in algal biomass, nutrient loading, and 

 sediment deposition, and decreases in submerged aquatic vegetation as a 

 result of human development (Brush, 1984; Brush and Davis, 1984; Davis, 

 1985; Orth and Moore, 1983b). In this paper I document past cycles in 

 eelgrass abundance with cores from bays on Cape Cod and Buzzards Bay, 

 Massachusetts. 



In temperate waters, eelgrass populations undergo major 

 fluctuations in abundance due to disease, storms, ice scour, and 

 pollution (Harlin and Thorn-Miler, 1981; Orth and Moore, 1983b; 

 Robertson and Mann, 1984, den Hartog, 1987). For example, the wasting 

 disease destroyed at least 90% of all eelgrass in the Western Atlantic 

 during 1931-32 (Rasmussen, 1977; den Hartog, 1987) and less dramatic 

 declines of eelgrass were reported along the eastern seaboard of the US 

 in 1894, in New England in 1908, and in Popponesset Bay (adjacent to 

 Waquoit Bay) during 1915 (Cottam, 1934). In recent decades, nutrient 



