COPPER ORE EXPERIMENT IN A LAGOON 



157 



Figure 5. — Copper concentrations (average of all station?) 

 showing approximate minimum lethal level from labora- 

 tory experiments. 



placed ill the lagoon. Again the results were 

 disappointing. A near lethal concentration was 

 attained but decreased during the next 5 months to 

 about 0.01 Mg-at./l- In some respects, the effects 

 of the ore were similar to those of copper sulphate 

 employed in the Florida red-tide control experi- 

 ments (Rounsefell and Evans, 1958). The rapidly 

 attained maximum levels soon decreased to nomial 

 values for the area. In the Florida control tests, 

 however, lethal levels were reached, and the 

 decline that followed occurred in a matter of days 

 rather than months. Undoubtedly, variation in 

 the hydrography and chemistry of the two areas 

 accounted for much of the difference in maximum 

 levels attained and also in the rates of decline. 

 The water of the lagoon is high in particulate 

 matter (fig. 6), and the copper from tlie ore was 

 assumed to have been adsorbed and made unavail- 

 able by the muds, plankton organisms, and other 



TURBIDITY 



(4 -INCH SECCHI DISC) 



Figure 6.— Turbidity of Ea-st Lagoon. Average Secehi 

 disk readings from stations. 



material making up I lie particulate matter 

 (Harvey, 1955). 



Zooplankton 



A qualitative and ([uantitative study of tiio 

 standing crop of zooplankKm in tiie lagoon was 

 made by Fleminger (1959). The outstanding 

 observation of his work was the broad summer- 

 abundance peak and secondary peak combined 

 with troughs in tlie early spring and autumn 

 (fig. 7). Of particular significance is tlie January 

 to March 1959 secoiulary peak which indicates 

 continued growth of zooplankton populations 

 following the addition of copper ore. 



Barnacle setting rate 



This study, conducted by Aldrich (1958a), 

 showed that the adult barnacle population of the 

 lagoon consisted almost exclusively of tlie brackish- 

 water species, Balanux ehurneus. Another 

 brackish -water species found occasionally was 

 Balanm improvisus. The data in figure 8 indicate 

 the seasonal nature of barnacle setting in the 

 lagoon. The outstanding feature is the con- 

 tinuance of tiie seasonal growth pattern after 

 addition of the ore. 



Prorocentnnn sp. 



Table 1 shows the initial and final counts of 

 Frorocentnun sp., and copper concentration of the 

 cultures in the dialysis bags used in the lagoon. 

 More than half of these cultures increased in 

 population count. The data indicate that the 

 greatest increase occurred in cultures liaving the 

 lowest initial count. Presumably, tliese had not 

 reached their peak when placed in the lagoon. 



The copper concentration apparently did not 

 interfere with the population growth of the 

 organism. Tliere was one exception: approxi- 

 mately 60 percent mortality occurred within llie 

 4-day bags placed at station 4 on October 10. 

 This was the day of tlie second ore addition 

 (table 1), and the day that tlie greatest concen- 

 tration of copper was observed witliin tiie hags. 



Live car organisms 



Laboratory experiments (Aldricii, 1958b) con- 

 ducted in conjunction witli the copper ore study 

 indicated tliat tiie snail l.ittorina irroiata was 

 probably most susceptible to copper poisoning. 

 Twenty-four-hour tests demonstrated, however. 



