For this experiment, Acartia tonsa was collected from the Choptank River at the Horn Point Laboratory in Cambridge, Maryland. Five individual experiments were done on male and female A. tonsa copepods, each with 3 replicate vials. Filtered Penicillin-Streptomycin Solution antibiotic seawater was used in each experiment and treated with nitrogen gas to create oxygen concentrations ranging from 1 mg L-1, 2 mg L-1, 3 mg L-1, 4 mg L-1, and 6mg L-1. The vials were then connected to a Pyro Science FireStingO2 Optical Oxygen Meter and placed in a 23.5ºC ± 0.5 water bath, and the oxygen concentrations in each vial was recorded for 15 hours.
The results showed that above the critical environmental oxygen partial pressure value of 9.57 kPa, respiration for both male and females were independent of the environmental oxygen partial pressure. Additionally, adult A. tonsa continued to respire and maintained their target respiration rate, as their respiration was independent of oxygen concentration. However, at lower environmental oxygen partial pressures, adult female copepods continued to respire rapidly decreasing the oxygen concentration in the experimental vials. Adult female A. tonsa was found to have higher respiration rates than males. When exposed to hypoxia at 2 mg L-1, average female respiration rate was 0.00393 µg O2 L-1 µg dry wt.-1 d-1, while the average male respiration rate was 0.1876 µg O2 L-1 µg dry wt.-1 d-1.