SFB754 Zooplankton respiration and ammonium excretion

Zooplankton metabolic rates (oxygen respiration and ammonium excretion) at different temperatures, oxygen, and carbon dioxide partial pressures (Kiko et al., 2015; 2016) were measured during three cruises. Zooplankton was collected by different nets and the entire catch immediately transferred to 10 l beakers containing pre-cooled seawater. Diel vertical migrators were sampled at the surface at night. Individuals for respiration rate measurements were isolated immediately and maintained in filtered seawater for 1 to 13 hours at the chosen experimental temperature (13, 18 or 23°C). Only animals appearing unharmed and fit were used for experiments. Water for the respiration and excretion rate trials was UV-treated, filtered over a 0.2 µm sterile filter, and supplemented with antibiotics (25 mg l-1 ampicillin and 25 mg l-1 streptomycin). Subsequently, the water was bubbled with different Gas mixtures (N2, O2, CO2, see Kiko et al., 2016 for details) adjusted to the chosen pO2 and pCO2 levels.