INFLUENCE OF DURATION OF INCUBATION ON ZOOPLANKTON RESPIRATION AND EXCRETION RESULTS

Respiration (O), ammonium (NH4), phosphate (PO4), total nitrogen (NT) and phosphorus (PT) excretions were measured on mixed zooplankton during 3-, 6-, 9-, 12-, 21-, and 24-h incubation periods at 20-23 C. The excretion rates of PO4, NT. and PT decrease during a 21-h period, while rates of respiration and excretion of NH{IN4} are constant. The percentage of inorganic nitrogen excreted increases regularly from 3 h (30-40% of total nitrogen) to 21 h (70-80%) and it could be either due to a bacterial activity which was measured or to a decrease with time of organic nitrogen excreted because of starvation. O NT, O PO4, O PT, and NH4 PO4 ratios increase during the first 9 h of incubation; the percentage of inorganic phosphorus excreted is higher at the very beginning and then remains constant from 6 to 24 h. O NH4 and NT PT ratios are constant during a 24-h term, which makes them useful metabolic indexes. © 1979.