Grazing and excretion by zooplankton in the Peru upwelling system during April 1977

M. Dagg, T. Cowles, T. Whitledge, S. Smith, S. Howe, D. Judkins

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70 Scopus citations


Rates of ingestion and excretion by adult females of the copepods Calanus chilensis, Eucalanus inermis, and Centropages brachiatus were measured in natural seawater during a cruise in the Peru upwelling system during April 1977. Simultaneously, zooplankton samples were collected for later determination of the abundance and distribution of these and other species. For these three organisms, feeding, and excretion rates of individuals are combined with information on the animal concentrations to estimate the grazing stress on the phytoplankton at each station, and to estimate the excretory nitrogen produced at each station. Comparison of grazing stresses with measured rates of primary production indicates that these large copepods were harvesting less than 5% of the daily phytoplankton production. Comparison of the nitrogen excretion rates with the amounts of excreted nitrogen in the water column indicates that less than 3% of the ambient excretory nitrogen was produced daily by these copepods. The importance of the abundant small zooplankton in the system is suggested.

Original languageEnglish (US)
Pages (from-to)43-59
Number of pages17
JournalDeep Sea Research Part A, Oceanographic Research Papers
Issue number1
StatePublished - Jan 1980

ASJC Scopus subject areas

  • Environmental Science(all)
  • Earth and Planetary Sciences(all)


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