54" 



I8 C 



NAPATREE PT 



50< 



WATCH HILL PT 



© 



'© 



SUGAR REEF 



9» 



/#. WATCH HILL REEF 



17 



CATUMB • 

 ROCKS 



4 ■•. 



© 



8 



© 



10 







•12 



15 



14 



— I8« 



I3» 



I 1 1 



54° 52° 50° 



Figure 3-1.— Watch HID, R.I., survey area. Location of grounding of Ocean 250 marked by asterisk. Benthic grab sampling stations marked by open circles. 



100 



i i I r 



2.0 1.4 1.0 0.7 0.5 0.35 025 0.18 0125 0.074 



DIAMETER (mm) 



other and not to substrate which was silty sand. All individuals were 

 less than a year old as indicated by their lengths ( <4 cm), single size 

 mode, absence of annual growth rings, and absence of fouling 

 organisms. Winter storms may move or bury portions of this soft- 

 bottom population. It is assumed that the extensive rocky substrate 

 in the area supports mussels which reach maturity. 



Data on the sizes of Eve mussels and of shells which are dead 

 but still articulated (clappers) are given in Figure 3-3. Gappers made 

 up a small, relatively consistent, proportion of each collection and 

 did not include the largest animals. Several had been drilled by 

 predatory gastropods. No clappers had tissue in their shells. It is 

 assumed that if a mussel had been killed or weakened by exposure 

 to gasoline within 2 d, tissue would have been present at the time 

 of sampling. 



The concentrations of hydrocarbons of 12, 10, and 3 ppb in 

 the water near Watch Hill Reef on 17 March (J. Lake et al., see sec- 

 tion 2.2) are well below the 5-50 ppm levels of soluble aromatic 

 hydrocarbons which are actually toxic to tested bivalves (Hyland 

 and Schneider 1976). Gilfillan (1975) commented on the relatively 

 high resistance of blue mussels to acute hydrocarbon exposure. 

 Mussels have been found to accumulate hydrocarbons in their 

 tissues when exposed to high concentrations of oil [1 ,000-5,000 ppm 

 dry weight in an oil spill area (Straughan 1977); 600-1,200 ppm dry 

 weight near a refinery effluent (Burns and Smith 1977)]. 



Figure 3-2. — Grain size distributions of representative benthic 

 grab samples from the survey area of the Ocean 2S0 spill. 



17 



