Carbon dioxide production rates of marine epipelagic copepods in subtropical waters during the late winter bloom

Carbon dioxide production rates of mixed epipelagic copepods were measured during the so-called late winter bloom in the vicinity of the Canary Islands. Respiration rates were measured using a simple and sensitive infra-red gas analyser coupled to a manifold containing an equilibrator module to transfer seawater CO2 to the gas phase. The system allowed the determination of the carbon dioxide content of one sample in 20 to 40 min. Respiration rates obtained were similar to previous oxygen consumption rates in subtropical waters. A relative wide range of carbon dioxide production rates was observed due to the metabolic condition of the organisms. Direct measurement of respiration rates after the capture showed high values (11-fold) compared to standard rates at starving conditions after only 4–6 h of incubation in filtered seawater. The results showed that short-term (0.5 h) CO2 production rates by copepods can be measured in relatively large incubation volumes (600 ml) minimizing crowding and bottle effects. A standardized method is proposed in order to obtain comparable results of metabolic rates in marine mesozooplankton.