1. A. nigra collected from illuminated areas along 

 the desalination plant sea wall had more than 

 five times the copper concentration found in 

 specimens collected at the control stations. 



2. A. nigra collected from illuminated areas had 

 1.5 times the amount of copper found in the 

 specimens collected from crevices along the 

 sea wall. 



The ten largest specimens collected from illuminated areas had an 

 average volume of 2.5cc. The ten largest specimens collected from 

 dark crevices had an average volume of 6.2cc. Since settlement of 

 these animals occurred in the first part of August (about 30 days 

 prior to collection) , it can be assumed that the A. nigra in the 

 darker areas grew about 2.5 times more rapidly than those in the 

 illuminated areas. 



It can be concluded from the results of the A. nigra studies that 

 copper was concentrated at a higher rate and was probably more toxic 

 in illuminated versus dark habitats. The mechanism for this metabolic 

 difference is not known, but illumination should certainly be considered 

 a key parameter when conducting copper toxicity studies either in the 

 laboratory or in the field. 



Correlations between the biological data and copper concentrations 

 recorded from the regular hydrographic samples were poor. As stated 

 above, this was due to periodic effusions with high levels of copper 

 which were (because of their brevity) impossible to measure in situ 

 at the biological stations. Only organisms which could avoid the 

 effusions would be expected to show a good correlation with the average 

 copper levels recorded at the biological stations. Barnacles showed 

 this conclusion to be true. Barnacles are able to completely seal their 

 shells with their operculum. When shut, the operculum protects the 

 barnacle from dessication at low tide or osmotic stress during expo- 

 sure to freshwater. Divers, during the study, noticed that the barna- 

 cles closed their opercula and ceased feeding when exposed to turbid 

 effusions containing high copper concentrations. Barnacles and ser- 

 pulids are the only surviving sessile organisms at Station 4, immed- 

 iately in the path of the discharge and their success at that station 

 may be due to their ability to isolate themselves from the effluent 

 when necessary. 



When 30-day settlement discs were analyzed, the largest barnacles 

 were measured to obtain an estimate of maximum barnacle growth 

 during that month. These growth rates were plotted against average 

 copper concentrations found at biological stations by regular sampl- 

 ing (Fig. 60). Two groups of stations were selected; Stations 3, 5, 

 and 6 near the effluent and Stations 2 and 7 farther away (see Fig. 

 3). The regression lines shown in Figure 60 do not differ significantly 

 in slope or elevation (P>.20 in a two-tailed F test), but do differ 



139 



