Temperature, salinity, dissolved oxygen, and pH were routinely measured in 

 the dosing tanks, and averaged 16°C, 31 ppt, 8.09 ppm, and 8.03 respectively. 

 Hydrocarbon concentration was also determined routinely by infrared 

 spectrometry, following the techniques described in Hyland, et al. (6). The 

 actual oil concentrations measured according to this method, are somewhat 

 different from the nominal ones mentioned previously. Accordingly, during the 

 exposure period the 0.01 ppm tank averaged 0.019 ppm above the natural 

 background hydrocarbon concentration; the 0.1 ppm tank averaged 0.06 ppm; 

 and the 1 ppm tank averaged 0.64 ppm. 



RESULTS AND DISCUSSION 



Figure 9-1 illustrates the feeding activity of Mytilus edulis prior to oil 

 exposure. There appears to be little difference in the shapes of the four feeding 

 curves; and, in fact, statistical analysis revealed no significant differences (P< 

 0.05). Typically, 80 percent of the food particles were removed by the mussels 

 in 1 5 minutes, and 95 percent in 30-minutes, at which point maximum filtering 

 activity was reached. Over this 30 minute interval, the average filtration rate 

 for the four groups was calculated as approximately 18.1 ml/min, which is 

 representative of values reported elsewhere in the literature (2). The values 

 ranged from 15.6 for the control; to 18.7 for the 1 ppm group, and 19.1 for 

 both the 0.01 and 0.1 ppm groups (Table 9-1). 



100 f— 



o 



E 

 o 



> 

 o 



E 

 » 

 q: 



o 



Q. 



CONTROL 

 0.01 ppm 

 0.1 ppm 

 1 .0 ppm 



o 



± 



60 

 TIME 



90 120 



(minutes) 



150 



180 



Figure 9-1. Pre-exposure: Comparison of Filtering Activity of 

 Mytilus edulis P rior to Exposure to W.A.F. No. 2 Fuel Oil. 



115 



