Stone crab and sea urchin cages were constructed from plywood and 

 steel hardware cloth. They survived eighteen months in the field 

 and provided additional data on wood boring organisms when dis- 

 mantled. 



Experimental animals were collected from outside the harbor area 

 by SCUBA divers. To minimize damage to the organisms, they were 

 handled as little as possible and transplanted to the cages and 

 holding sites within a few hours of collection. Effects of the 

 transplantation techniques were evaluated from survival at the 

 control station (Station 10). 



LABORATORY BIOASSAY 



Laboratory 96-hr TLm acute bioassays were conducted on the same 

 species used for the i-n situ bioassays to determine the relative 

 toxicity of the fresh effluent from the desalination plant and to 

 isolate the most toxic features of the effluent. The experimental 

 design used is shown in Figure 7. The experiments began by conducting 

 static 96-hr TLm acute bioassays (Doudoroff et at 1951) of fresh 

 effluent in 50 liter, all glass aquaria. A wide range of effluent 

 dilutions, plus a control, assured sufficient data points to make the 

 interpretation valid. 



Each dilution contained ten experimental animals and the 96-hr TLm 

 experiments were run at least twice to obtain replicate data. 

 Samples of the effluent dilutions were taken daily to ascertain 

 levels of oxygen, pH, copper, salinity, and temperature in the 

 aquaria. 



The experiments were complicated by the variability in copper content 

 of the effluent and by the unpredictable operation of the desalination 

 plant. Obviously, if the plant shut down on a day when effluent was 

 needed for the bioassays, the experiment had to wait until the plant 

 resumed operation and became stabilized. 



Following the determination of the 96-hr TLm doseage, a second 

 experiment was set up to isolate the major parameters of the effluent 

 to determine which parameter was most toxic (Fig. 7). Copper, 

 salinity, and temperature were independently elevated in normal, 

 filtered seawater to a level comparable to that found in the 96-hr 

 TLm effluent dilution. 96-hr TLms were then conducted for these 

 individual parameters. Salinity was raised by the addition of 

 artificial dried seawater ^salts , copper was raised by the addition of 

 copper sulphate salts and temperature was raised by thermostatically 



controlled, glass protected heating units. 



Bioassays on the turtle grass, Thalassia testudinum, were conducted usino 



36 



