FISHERY BULLETIN: VOL 76, NO. 2 



metabolic response patterns of £. acutifrons to the 

 normal fluctuations found in estuarine systems 

 were significantly altered by the water quality of 

 Santos Bay water. 



MATERIALS AND METHODS 



The copepods were collected in two fixed loca- 

 tions off the coast of the State of Sao Paulo, one in 

 Santos Bay (lat. 23°59'S; long. 46"19'W), the 

 other in Sao Sebastiao Channel (lat. 23°50'S; 

 long. 45°25'S). Collections were made with a 

 nylon plankton net (20 m/x) during the winter 

 when water temperatures averaged approxi- 

 mately 21°C. All samples were brought im- 

 mediately into the laboratory whereupon E. 

 acutifrons were sorted from the plankton using a 

 mouth pipette under a binocular microscope. The 

 copepods were placed in 2-1 crystallizing dishes, 20 

 cm in diameter and 15 cm high. In the first two 

 series of experiments, the copepods were placed in 

 the water obtained from the collection points, i.e., 

 copepods from Sao Sebastiao Channel were placed 

 in Sao Sebastiao water (35%o) and copepods from 

 Santos were placed in Santos water (28%o). In the 

 last two series of experiments, copepods from Sao 

 Sebastiao were placed either in Santos water or in 

 Sao Sebastiao water diluted to 28%o. The copepods 

 were maintained under temperature and photo- 

 period regimes approximating field conditions: 

 19°-24°C and 11 L:13 D. The copepods were fed 

 with Phaedactylum and Platymonas daily and 

 kept in the laboratory at least 1 wk before being 

 used in the respiration experiments. 



Oxygen uptake was determined using Carte- 

 sian diver respirometers (Holter 1941), which 

 have a total volume of 8-13 />tl. Only nongravid 

 females were used. Two or three copepods were 

 placed in each diver, depending upon the salinity/ 

 temperature regime of the experiment. The oxy- 

 gen uptake was determined during a 2-h interval. 

 The first 30-min reading was discarded; after this 

 initial reading, uptake rates remained constant. 



Oxygen uptake rates were measured under the 

 following environmental conditions: Sao Sebas- 

 tiao animals maintained in Sao Sebastiao water, 

 Santos animals in Santos water, and Sao Sebas- 

 tiao animals in Santos water, 15°, 20°, 25°, 30°, 

 and 32°C at 15, 25, 35, 45, and 55%o salinities. The 

 oxygen uptake of Sao Sebastiao animals main- 

 tained in Sao Sebastiao water diluted to 28%o was 

 determined at 15°, 25°, and 30°C over the same 

 salinity ranges used in the other experiments. Ten 



determinations were made under each set of en- 

 vironmental conditions. Distilled water or freeze- 

 concentrated brine was added to filtered seawater 

 to attain the desired salinities. Salinities were 

 determined by titrating against silver nitrate 

 (Harvey 1955). 



Dry weights for the copepods were obtained 

 using a TorbaP torsion balance, 0.01 mg sensitiv- 

 ity. The copepods were rinsed with distilled water 

 and dried at 70 °C for 24 h before they were 

 weighed. Three replicates of 200 nongravid fe- 

 males from each area of collection were used. Re- 

 sults were expressed as microliters of oxygen per 

 milligram per hour. Significant difference of 

 means was calculated by the method of Simpson et 

 al. (1960) for small samples. 



The metabolic data obtained in the first three 

 series of experiments were analyzed statistically 

 using multiple regression techniques. The basic 

 experimental design used in this study is usually 

 referred as a factorial design. Specifically, the plan 

 was a 5 X 5 factorial using five levels of tempera- 

 ture and five levels of salinity, making in all 25 

 combinations of experimental conditions. Since 10 

 determinations of oxygen uptake were made in 

 each combination, a total of 250 observations were 

 made in each series. Thus, the 250 observations 

 may reasonably be considered as continuous re- 

 sponses of a function of the two factors and interac- 

 tions. 



Oxygen uptake data were analyzed as percent- 

 age of oxygen consumption relative to that at 

 25°C and 35%o salinity for Sao Sebastiao animals 

 in Sao Sebastiao water and at 25°C and 25%o salin- 

 ity for Santos animals in Santos water and Sao 

 Sebastiao animals in Santos water, i.e., the rate 

 under these "standard" conditions was assumed to 

 be lOO'/f , and rates obtained under other regimes 

 were calculated as the percent deviation from that 

 rate. Since the observations are treated as percent- 

 age measurements generated by data from bino- 

 mial populations, the transformation Y = arc sin 

 v'jc, where x is observed percent respiration, is 

 appropriate to stabilize variances (Mendenhall 

 1968). Analysis of variance for this data indicated 

 which of the factors (temperature, salinity, or 

 temperature-salinity interactions) had significant 

 effects on the metabolism of the copepods. The 

 program was run on an IBM 360 computer. 



''Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



450 



