of the discharge pipe. Serpulids (by far the most common macroin- 

 vertebrate in Safe Harbor) also inhabited rocks in the immediate 

 vicinity of the discharge and they also had opercula to seal the 

 ends of their calcium carbonate tubes. 



Comparison of average copper concentrations (without the effusion 

 copper) and barnacle growth rates proved the barnacles were not 

 exposed to the transient high levels of copper associated with effu- 

 sions. Divers also confirmed that opercula of barnacles exposed to 

 effusions were closed and that barnacles did not feed during exposure. 

 Serpulids were also withdrawn and not feeding during exposure to the 

 effusions . 



Sabellids are also tube-worms but these do not have opercula to seal 

 the entrance to their parchment-like tubes. Although they were common 

 in Safe Harbor in the summer of 19 70 and again in the summer of 19 71 

 (after copper discharges had been reduced) , they had a mass mortality 

 in October, 19 70 and were relatively rare at the biological stations 

 in the harbor throughout the fall, winter, and spring of 19 70-71. 



Laboratory bioassays confirmed the hypothesis that copper was the most 

 toxic element of the effluent. Except for ascidians, copper explained 

 the observed mortalities in acute bioassay studies. Although the 

 ascidians were also susceptible to copper toxicity, the effluent was 

 more toxic than could be explained by the copper contained in it. It 

 was suggested, but not proven or explained, that synergism of copper 

 and temperature may be more pronounced for ascidians than for the other 

 organisms investigated. 



ASSESSMENT OF EXPERIMENTAL DESIGN 



In setting up the experimental design for this investigation, the re- 

 searchers included experiments which would adequately delimit the 

 biological impact of the effluent. Most of the techniques had shown 

 success in other ecologically-oriented pollution research but some of 

 the techniques had not been tried before. The final experimental 

 design, therefore, included experiments which final analysis showed to 

 be redundant or unproductive or more laborious than the information 

 gained was worth. It is worthwhile to discuss the relative value of 

 the various experiments for the benefit of other workers involved in 

 similar studies. 



The experiments are outlined below with the most productive experiments 

 listed first under the two headings Effluent Dispersion and Biological 

 Investigations. 



