observed mortalities, each of these parameters was raised indepen- 

 dently in separate analyses (Fig. 7). Salinity, even when raised 

 to the equivalent of 30 percent effluent (40.2 o/oo) produced no 

 mortalities. 



Copper was added to seawater as the cupric sulfate salt (CuS0i+5H20) 

 and its toxicity tested using the same 96-hr static acute bioassay 

 methods. Results of these bioassays were compared with bioassays 

 of equivalent amounts of copper found in the dilutions of effluent 

 (Figs. 56 through 59). Figure 56 shows that 100 ppb copper was 

 present in the effluent dilution which caused 50 percent of the 

 echinoid mortalities in 96 hours and that the toxicity of 105 ppb 

 cupric copper in normal seawater was sufficient to cause the same 

 mortality. Copper, therefore, was the sole toxic constituent in 

 the effluent required to explain the observed echinoid mortalities. 

 Similar results were found in the copper toxicity experiments with 

 stone crabs (Fig. 57) and turtle grass (Fig. 58), although these 

 organisms were on the whole less sensitive to copper than either 

 echinoids or ascidians. 



Copper toxicity did not explain all of the observed toxic effects 

 of the effluent for specimens of Asoidia nigra (Fig. 59). One 

 hundred and fifty ppb ionic copper were required to kill 50 percent 

 of the experimental specimens of A. nigra when the copper was dis- 

 solved in seawater but the same mortality occurred with effluent 

 which contained only 80 ppb copper. Asoidia nigra, therefore, was 

 also sensitive to some other contaminant of the effluent, or to the 

 interaction of the various contaminants. Zeitoun et at (1969), 

 Lloyd (1965) and others have shown synergistic effects of copper 

 with temperature and perhaps these are more pronounced for the filter 

 feeding ascidians than for the other organisms tested. Alternatively, 

 other contaminants in the effluent (i.e., nickel) may have had a 

 greater affect on A. nigra than on the other organisms. 



Although temperature tolerance tests showed the experimental organisms 

 were within a few degrees of their lethal limits, the temperature 

 elevations caused by the 96-hr TLm dilutions were within normal sea- 

 sonal ambient ranges. Temperature, by itself, was not lethal to the 

 test animals at the 96-hr TLm effluent dilutions. Asoidia nigra and 

 Lyteohinus variegatus showed an abrupt increase in mortality at 

 about 32°C. At temperatures at or below 31°C all specimens of both 

 species survived more than 96 hours. When temperatures were at or 

 above 32° C more than 50 percent of the experimental specimens of both 

 species died within 96 hours. 



A temperature of 32°C represents the heat of an effluent dilution of 

 20 percent in the acute bioassay experiments. Since the 96-hr TLm 

 dilution of the effluent for L. variegatus was about 9 percent (about 

 31°C) and that for A. nigra about 6 percent (about 30.5°C), tempera- 

 ture alone could not account for the observed mortalities. 



131 



