Table 9-1. Filtration Rates for Control and Oil-Exposed Mussels. 
NOTE: Mean and standard error (in parentheses) are both given. 
Control 
0.01 
ppm 
0.1 
ppm 
1.0 
ppm 
Pre-exposu re 
15.6 
19.1 
19.1 
18.7 
(0.4) 
(0.4) 
(1.9) 
(1.5) 
48-hr. Exposure 
19.3 
10.5 
5.2 
2.2 
(3.3) 
(0.9) 
(0.5) 
(0.2) 
2-wk. Exposure 
17.8 
5.3 
1.8 
0.3 
(1.5) 
(0.3) 
(0.5) 
(0.04) 
24~hr. Recovery 
15.8 
9.9 
3.9 
0.8 
(0.2) 
(1.2) 
(0.2) 
(0.1) 
2-wk. Recovery 
30.9 
— 
30.9 
17.2 
(6.5) 
(6.5) 
(1.6) 
After 48 hours of exposure (Figure 9-2), the filtration curves for the three 
experimental groups began to diverge, while the control curve retained 
pre-exposure characteristics. Mussel feeding activity in all three oil 
concentrations was significantly reduced from that of the control, with the 
highest concentration producing the most severe reduction. Filtration rates for 
the 0.01 ppm, 0.1 ppm, and 1 ppm polluted mussels, decreased to 10.5, 5.2 
and 2.2 ml/min, respectively, while the control group Filtered at an average rate 
of 19.3 ml/min. Figure 9-3 illustrates that continued oil exposure produces 
progressively lower Filtration rates. Mussels exposed for two weeks to 0.01 ppm 
required two hours to Filter what the controls Filtered in 30 minutes. Similarly, 
after three hours, animals exposed to 1 ppm had only consumed approximately 
35 percent of the algae; while the controls far surpassed this in less than 10 
minutes. After two weeks of exposure, filtration rates for the three exposed 
groups decreased to 5.3, 1.8, and 0.3 ml/min, while the control group Filtered 
at an average rate of 17.8 ml/min. 
Following the two-week exposure period, the animals were returned to clean 
water. Some evidence of recovery was noted after 24 hours in clean water 
(Figure 9-4); however, the filtration curves for all three exposure groups were 
still significantly different from the control. Filtration rates increased to 9.9 
ml/min for the 0.01 ppm group, 3.9 ml/min for the 0.1 ppm group, and 0.76 
ml/min for the 1.0 ppm group. 
116 
