During the gathering of growth and survival data on Asoidia nigra, 

 divers noted animals in protected environments survived better and 

 grew faster than those in exposed locations. A survey of other 

 copper sensitive organisms in Safe Harbor confirmed that those in 

 sheltered, dark locations (under ledges, in caves, and behind sub- 

 merged structures) also were larger and settled more densely than 

 those in illuminated habitats. The same relationship did not appear 

 in sites beyond the extent of the effluent. 



According to Steemann Nielsen and Wium-Andersen (1970) , copper toxicity 

 occurs in Chlorella only in the light. When Chlorella were treated 

 with copper but left in light-proof containers, they experienced no 

 toxic effects until exposed to light. Perhaps a similar mechanism 

 influences copper toxicity in invertebrates. 



Normally, Asaidia nigra, which is a filter feeder, grows faster in 

 unsheltered environments, where currents can circulate more freely. 

 In the copper-rich Safe Harbor environment, however, animals pro- 

 tected from strong light outgrew those in more exposed positions. 

 The effect of light on copper toxicity may explain this phenomenon 

 and may also explain the settlement and success of organisms on only 

 the lower surfaces of settlement panels. During the preliminary survey, 

 Clarke (unpublished data) , organisms settled equally successfully on 

 the top and bottom of panels. From August, 1970 to August, 1971 the 

 upper surfaces of the settlement panels were almost entirely barren of 

 organisms after the normal exposure period, while serpulids, sabellids, 

 and barnacles grew rapidly on the lower surfaces. 



To determine if copper uptake and toxicity were influenced by illumi- 

 nation, specimens of A. nigra were collected from the desalination 

 plant sea wall and from the control station in September, 1971. 

 Specimens from the sea wall were collected from exposed, highly illumi- 

 nated areas as well as from the dark situations in crevices in the sea 

 wall. These were analyzed for total copper content by the method 

 described in Appendix A. 



Copper concentration in A. nigra specimens from the control station 

 averaged 39 ppm; a concentration 2,300 times the ambient copper levels 

 found in seawater at that station during the preceding four months. 

 Copper concentrations in specimens from the illuminated portions of 

 the sea wall at the desalination plant averaged 202 ppm; a concentra- 

 tion of 5,000 times the levels recorded in the water at that station 

 during the months that A. nigra commenced resettling on the wall. The 

 copper levels recorded from water at the sea wall station were, how- 

 ever, lower than actually occurred there during the periodic, trans- 

 ients of high copper concentrations associated with effusions follow- 

 ing maintenance periods. The specimens collected from darkened crevices 

 had copper concentrations of 132 ppm. The following findings emerge 

 from these analyses: 



138 



