Zooplankton data were limited. Some samples had to be acidified 

 to remove excessive amounts of silt. Acid treatment, of course, 

 made zooplankton counts unreliable. The data obtained showed a 

 decrease in zooplankton populations in effluent-laden water. In 

 October, the deep tow at the desalination plant yielded only 

 39.87 percent of its potential population compared to the shallow 

 tow. In December, the zooplankton population in the deep tow was 

 only 14.28 percent of its theoretical level. In April, the desali- 

 nation plant was not operating and the zooplankton in the deep tow 

 reached 167 percent of its theoretical population. 



SETTLEMENT PANELS 



Settlement panels provided data on the distribution and abundance 

 of a variety of sessile filter feeders in Safe Harbor. For the first 

 four months different materials were used for the panels to determine 

 which surface provided the most suitable substrate for both settlement 

 and analysis. By November, plywood panels were selected as the best 

 material and analytical procedures were stabilized (see Section IV 

 Methods and Procedures). 



Monthly collections were carried out for twelve months, from November, 

 1970 to October, 1971. During the yearly cycle, three organisms 

 dominated the panels; serpulid worms (Hydroides norvegica) , sabellid 

 worms (Branokiomma nigvomaculata) , and barnacles (Balanus amphitrite 

 niveus) . Other organisms which settled on the panels included hydroids, 

 filamentous red and green algae, tunicates and bryozoans. These latter 

 organisms occurred so infrequently at the stations that they were of 

 little quantitative value. They became more abundant beginning in 

 July, 1971 and reached a peak for the year in August and October. This 

 peak was not present during the previous year and it is probable that 

 the drop in copper discharge levels which began in June contributed to 

 the improvement of living conditions for these organisms. 



From November, 1970 to May, 1971, the settlement panels yielded an 

 almost unispecific settlement of serpulid worms; a condition reflected 

 in transect and quadrat analyses of the benthic fauna. Figures 37 

 through 40 show the distribution and abundance of the serpulid worms 

 during the twelve month study period. They were most abundant in 

 November, 1970. Their numbers gradually decreased until June, 1971 

 when there was a sudden change in the pattern of distribution of the 

 worms and a marked decrease in their total abundance throughout the 

 harbor. While the serpulid worms were clearly more tolerant of the 

 effluent than other sessile organisms, the marked reduction in their 

 numbers at Station 3C (Figs. 39 and 40) compared with adjacent stations 

 clearly shows the deleterious impact of the effluent. This adverse 

 effect is also brought out in Figure 41 which shows the mean number 

 of serpulid worms at each station during the entire year. More serpulids 



102 



