35 



from the depth of the wasting disease event, plant community changes, 

 sea level rise, and cores taken elsewhere. For example, tidal records 

 inicate that sea level is rising relative to the land in the northeast 

 U.S. at a rate of 2-3 mm y~ during the last 2 centuries (Emery, 1980) . 

 Because depths of local undredged, quiescent areas have changed little 

 on maps during the last 100 years, sedimentation in many areas, are 

 probably within a factor or two of the sea level rise rate. Some cores 

 show community transitions from recent Zostera beds to Ruppia beds to 

 the salt marsh grass Spartina with increasing depth, indicating that 

 overall, sediment deposition rates were less than sea level rise rates. 

 In Chesapeake Bay, recent sedimentation rates for cores taken in 

 quiescent areas ranged from 2 to 10 mm y"-^, and higher near rivers 

 (Brush, 1984; Davis, 1985). In Boston Harbor, sedimentation rates near 

 a sewage outfall were as high as 30 mm y~^ (M. Bothner, pers. comm.). 

 Lower rates may be typical for undisturbed areas in bays on Cape Cod 

 because river discharges are small. For example, if local sediment 

 deposition is 2-10 mm year, declines in seed abundance due to the 

 wasting disease can be expected to occur between 10 and 40 cm in cores. 

 Of course channels, deeper basins, sites near barrier beaches, dredged 

 areas, or streams may experience considerably higher rates of deposition 

 or even sediment removal. 



Methods 



To determine regional fluctuations in eelgrass abundance, nine 

 cores were taken in 4 bays around Cape Cod (Fig. 1) . One core was taken 

 in the north central region of Apponagansett Bay, So. Dartmouth (core 



