Table 18-4. Percent mortality and development time to cyprid 
of Balanus improvisus larvae following 24 hour exposure of 
stage II nauplii to different copper concentrations at 26°C. 
Cu 
(ppb) 
N 
Mortality 
(%) 
Days to Cyprid 
Range 
Mean 
3 
75 
19 
7-15 
10.2 
25 
81 
25 
7-15 
10.7 
47 
59 
19 
8-16 
11.7 
77 
64 
19 
9-16 
12.6 
98 
77 
25 
9-14 
11.6 
150 
76 
61 
8-15 
10.3 
190 
70 
100 
— 
— 
NOTE: During the post-exposure period, larvae were reared on a mixed algal 
diet of Tetrase/mis suecia and Tha/assiosira pseudonana at 26 ± 1°C. 
Swimming speeds of the above nauplii were significantly (p=0.01) increased 
at 25 and 50 ppb Cu relative to controls, nearly indentical at 98 ppb Cu, and 
significantly decreased at 150 ppb Cu (Figure 18-6). Although MLV of control 
and 98 ppb Cu populations were equal, the rate of change of direction (RCDI 
— absolute value of angular velocities in degrees/second) was substantially 
different (Table 18-5). These data show that the nauplii not only changed 
swimming speeds but also tended to change swimming patterns with increasing 
concentrations of Cu. Examples of path outlines and their computer assigned 
RCDI values are shown in Figure 18-7. 
Table 18-5. Rate of Change of Direction (RCDI) and 
Mean Linear Velocities of Balanus Improvisus Stage II 
Nauplii after 24 Hour Exposure to Indicated 
Copper Levels at 26°C 
Cu 
(ppb) 
N 
Linear Velocity 
(mm/sec) 
RCDI 
(deg./sec) 
3 
40 
0.82 
130 
24 
40 
1.43 
140 
57 
40 
1.23 
151 
98 
40 
0.83 
166 
151 
29 
0.49 
188 
283 
