MOREIRA and VERNBERG: SYNERGISTIC EFFECTS OF ENVIRONMENTAL VARIABLES 



RESULTS 



Animals From Sao Sebastiao 

 in Sao Sebastiao Water (35%o) 



The metabolic rate ofEuterpina acutifrons from 

 Sao Sebastiao which were maintained in water 

 from Sao Sebastiao Channel was less influenced 

 by changes in salinity than were the other groups 

 o{ E. acutifrons (Figure 1). Rate did, however, in- 

 crease with increasing temperature up to 30°C; at 

 32 °C, rates either leveled offer decreased. Great- 

 est increases in respiration rates were observed 

 between 15° and 20°C. These increases are 

 reflected in the relatively high metabolic rates 

 within this thermal range obtained from this 

 group of animals. 



At 20°C metabolic rates were not significantly 

 different over the entire salinity range of 15-55%o, 

 and at 15°C the copepods were able to regulate 

 their metabolism over a range of 25-55%o. At 

 higher temperatures (25°, 30°, and 32°C) rates 

 generally were lower at the salinity extremes (15, 

 45,55%o) and highest at 35%o. Rates varied from a 

 minimum of 4.87 to a maximum of 22.36 /xl/mg h ^^ 

 dry weight (Figure 1). 



Statistical analysis indicated that 66% of the 

 observed variability in the rates could be 

 explained by the temperature-salinity combina- 

 tions (Table 1), although the linear effect of tem- 

 perature was the single significant factor (1% 

 level). The linear effect of salinity, the quadratic 

 effects of the temperature and salinity, and the 

 temperature-salinity interaction did not contri- 

 bute significantly to the observed changes in res- 

 piration rates. Figure 2A shows the response sur- 

 face contours fitted over the experimental design. 



Table l. — Analysis of variance of data for 

 Euterpina acutifrons (Sao Sebastiao animals 

 in Sao Sebastiao water, 35%o). T = tempera- 

 ture, S = salinity. 



Animals From Santos in 

 Santos Water (28%o) 



In the Santos animals maintained in Santos wa- 

 ter, the rate of oxygen uptake also increased over 



the temperature range to 30°C for the entire salin- 

 ity range. In most of the salinities, the largest 

 metabolic increase occurred between 25° and 

 30°C. This contrasts with Sao Sebastiao copepods 

 which exhibited the largest increase between 15° 

 and 20°C. The Santos animals did not show the 

 metabolic regulation observed in the Sao Sebas- 

 tiao animals maintained in Sao Sebastiao water, 

 and tended to have low metabolic rates at the 

 salinity extremes, i.e., 15, 45, and 55%o. Highest 

 rates occurred at salinities of 25-35%o. The rates 

 varied from a minimum of 7.97 to a maximum of 

 28.20 Atl/mg h^Mry weight (Figure 1). 



Statistical analysis indicated that only 46% of 

 the observed variability in the respiration rates of 

 these animals could be explained by the 

 temperature-salinity combinations (Table 2). The 

 significant factors were the quadratic effects of 

 temperature and salinity (0.05% level) and the 

 linear effect of salinity (0.05% level). The 

 temperature-salinity interaction was not a sig- 

 nificant factor. Figure 2B shows the response sur- 

 face contours fitted over the experimental design. 



Table 2. — Analysis of variance of data for 

 Euterpina acutifrons (Santos animals in San- 

 tos water 28%o). T = temperature, S = salin- 

 ity. 



Variable 



Significance level 



T2 



S^ 



S 



T X S 



024350 

 0,28955 

 046193 

 046198 



0.05% 



0.05% 



0.05% 



Not significant 



Animals From Sao Sebastiao in 

 Santos Water 



Transfer of Sao Sebastiao copepods into water 

 from Santos markedly altered their metabolic re- 

 sponses, especially their response to salinity. Res- 

 piration rates increased with temperature up to 

 25°C at the extreme salinities (15, 45, 55%o) and 

 up to 30°C at salinities of 25 and 35%o, before 

 leveling off or decreasing. The copepods which 

 were transferred to Santos water did not regulate 

 metabolically at any temperature at the salinity 

 extremes. Lowest rates were obtained at salinities 

 of 15 and 55%o, and the highest rates were ob- 

 served at 25%o at 15° and 25°C. At 30° and 32°C, 

 peak metabolic rates occurred at 35%o (Figure 1). 

 Rates varied from a minimum of 6.80 to a 

 maximum of 37.23 /xl/mg h^ dry weight (Figure 

 1). 



451 



