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 15 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). 
Figure 9-1. Pre-exposure: Comparison of Filtering Activity of 
Mytilus edulis Prior to Exposure to W.A.F. No. 2 Fuel Oil. 
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