44 



Portland Harbor although stations with values well above the mean are 

 found scattered throughout the Bay (Fig. 18). Low values are again 

 grouped in the outer shipping channel and offshore of the islands. 



whereas upland drainage may be an important source of metals 

 deposited in coastal sediments, it does not seem to explain the elevated 

 levels in the Fore River (called the Stroudwater River in its non-tidal 

 portion). The Fore River has a small drainage area (28 sq. miles) 

 relative to the two other principal rivers entering Casco Bay, the 

 Presumpscot (590 sq. mi.) and the Royal (142 sq. mi.), which show little 

 or no elevation of metal levels near their mouths. In addition, above 

 Portland, the Fore River is largely surrounded by tidal marshes and 

 residential developments serviced by municipal sewers which discharge 

 elsewhere. It seems likely, therefore, that the elevated metal levels 

 in Portland Harbor sediments result from anthropogenic introductions 

 within the harbor and the industrialized lower Fore River estuary. 

 Additional sampling above Portland will be required to prove this 

 hypothesis . 



Linear correlations were computed for the six metals as well as 

 percent organic carbon and mean grain size on the phi scale (Table 5). 

 This analysis shows that, as demonstrated elsewhere (i.e. de Groot et 

 at., 1976), metal levels in Casco Bay surficial sediments are highly 

 correlated with fine grained sediment and levels of organic carbon. 

 That these factors are significant is a reflection of the large surface 

 area of fine-grained sediments and the sorptive capacity of many organic 

 compounds. These relationships help to explain the areal distribution 

 of the metals as, for example, the uniformally low levels encountered in 

 the coarse sediments in the main entrance to Casco Bay. 



