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The excretion of dissolved inorganic and organic phosphorus by several species of marine crustaceans and a planktonic rotifer was measured under laboratory conditions. The rate of excretion decreased as bacterial activity and duration of experiments increased and was directly related to temperature and salinity. Excretion rates were higher in early evening than at other times of day. The daily phosphorus requirements of the phytoplankton, calculated from 14 C measured rates of production and an assumed C : P ratio of 40 : 1, were compared with phosphorus released by zooplankton. The rates of excretion and the abundance of zooplankton were used to calculate an average daily addition of inorganic phosphorus to the photic zone. In Bras d’Or Lake, zooplankton released twice the average daily phytoplankton phosphorus requirement; in Morrison’s Pond, only one‐fifth was supplied by animal excretion. Microzooplankton excretion (not considered in this study) may explain the discrepancy between phytoplankton requirements and regeneration rate in Morrison’s Pond. Phosphorus supplied from the hypolimnion by eddy diffusion in Bras d’Or Lake was one‐tenth that regenerated by the zooplankton.
Hargrave et al. (Mon,) studied this question.