Etude de la respiration et de l'excrétion d'azote et de phosphore des populations zooplanctoniques de l'upwelling mauritanien (mars–avril, 1972)

Fiftysix experiments were run for 22 h on 200 μ-net zooplankton in non-filtered sea water. The equations of orthogonal regression lines between respiration, and mineral, total nitrogen, and phosphorus excretion rates have been computed for 14 stations in the upwelling Mauritanian area. Correlation coefficients are high: excretion values may be estimated from respiration values in order to follow the N and P flux through the Mauritanian zooplanktonic populations. O:N, O:P, N:P, mineral:total excretion ratios are calculated for each station and are not significantly different in the 3 areas of the upwelling area studied. On the average, 48% of excreted phosphorus is thoroughly oxidized into phosphate and needs 142.4 atoms in respiration per P atom. The remainder, excreted as organic phosphorus, requires the same amount of oxygen for its later mineralization. The O:P ratio thus obtained is close to the theoretical -276. Fiftyfour percent of the nitrogen excreted is mineral and the O:N-NH ₊ ⁴ ratio shows a dominant carbohydrate and fat catabolism. The N:P ratio is constant, and close to 10 for both mineral and total excretion.