Urea supply from decomposition and excretion of zooplankton

Rates of urea supply from the decomposition and the excretion of zooplankton were determined for samples collected in Suruga Bay. Five species of Zooplankton were incubated in filtered seawater at 20‡C for 276 hrs after being forced to die in a refrigerator. More than 77.6 % of body nitrogen of the Zooplankton was liberated, except forEuphausia similis, which showed a lower decomposition rate of 53.0 %. In the liberated nitrogen. 4.8 to 9.8 % was determined as urea. Incubation experiments of two species of zooplankton at 13‡C during 12 hrs, showed that the organisms excreted 0.86 and 0.73Μg-at. N indi.⁻¹ d⁻¹ as total soluble nitrogen. Urea accounted for 8.3 and 6.8 % of the excreted total soluble nitrogen.