100 t- 



E 

 p 



> 

 o 



E 



o 



CONTROL o 

 0.1 ppm A 

 1.0 ppm ■ 



_L 



A. 



1 



I 



60 

 TIME 



90 120 



(minutes) 



150 



180 



Figure 9-5. Two-week Recovery: Comparison of Filtering 

 Activity of Mytilus edulis after Two Weeks of Recovery from 

 Two Weeks Exposure to W.A.F. No. 2 Fuel Oil. 



feeding over a long period of time as a result of continued oil exposure. A 

 question confronted, for example, is whether mussels exposed for several 

 months to chronic inputs of oil reveal reduced growth. 



The laboratory experiments reported herein were designed to investigate 

 responses to chronic oil pollution, and not the acute phenomena which occur 

 immediately after an oil spill. However, in November, 1976, a small spill of No, 

 6 fuel oil occurred at Quonset Point, Rhode Island. The resulting slick drifted 

 across the westem passage of Narragansett Bay, and impacted approximately 

 one mUe of shoreline on Conanicut Island. This incident provided an 

 opportunity to investigate the effects of spilled oil on filtering activity in 

 mussels, and thus supports the laboratory results with field data. Accordingly, 

 48 hours after the spiM, Mytilus were collected from the polluted site and from 

 an unimpacted area nearby. Filtration rates were measured in the laboratory, 

 and feeding curves were generated for both groups (Figure 9-6). Compared to 

 controls, a small but statistically significant reduction in feeding activity was 

 observed in oiled mussels. For example, over a period of 45 minutes, the 

 controls had removed approximately 96 percent of the food particles, while 

 the polluted mussels removed only 84 percent. Filtration rates were calculated 

 as 7.2 ml/min (S.E. = 1.0) for the controls, and 4.9 ml/min (S.E. = 0.5) for the 

 oiled group. The relatively low value obtained for the control group is most 

 likely a reflection of low winter ambient water temperatures (5-6°C). One 



119 



