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 N Mortality Days to Cyprid 



(ppb) (%) Range Mean 



NOTE: During the post-exposure period, larvae were reared on a nnixed algal 

 diet of Tetraselmis suecia and Thalassiosira 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 N Linear Velocity RCDI 



(ppb) (mm/sec) (deg./sec) 



0.82 130 



1.43 140 



1.23 151 



0.83 166 



0.49 188 



283 



