45 



been observed elsewhere nutrient loading has increased (Orth and Moore, 

 1983b) . 



If deposition rates prior to the wasting disease are equal to 

 post-disease rates, then the date of the first pre-wasting disease 

 decline appeared circa 1902-1906 for all four Waquoit Bay cores. In 

 addition, the two cores (WB3 and WB4) with the earliest depositional 

 records indicate an even earlier decline circa 1870-1890. 



The cause of the 1902-1906 has several plausible explanations. 

 Some shallow coastal lagoons on Cape Cod close periodically, and a 

 closure of Waquoit Bay would reduce mouth would reduce salinity in the 

 Bay and possibly change water transparency. It is unlikely that Waquoit 

 Bay had become fresh during the last 100 y because all nautical charts 

 to 1865 Waquoit Bay with a prominent channel at the mouth, and marine 

 species persist throughout the core including when eelgrass is absent. 



Another possibility is that some other factor caused water 

 transparency to decline, and eelgrass disappeared from the deep areas 

 where the cores were taken. This seems unlikely, because prior to 1931, 

 there was little development around the Bay. Farms were common, but 

 levels of fertilization were far less prior to the use of manufactured 

 fertilizer. Cape Cod has undergone considerable deforestation and 

 conversion to farmland in the past, and topsoil runoff on nutrient 

 release from soils could have been a contributing factor, but this too 

 seems unlikely because river flow into the bay is nominal. 



Instead the most plausible explanation is that these declines 

 coincide with the eelgrass population collapse reported by Cottam in 

 1908 or 1894. 



