Interactions between phytoplankton and zooplankton abundances were examined with a zooplankton sampling system in the surface waters of the upwelling zone off Peru (15°S) in April 1977. Distributions of temperature, phytoplankton (expressed as chlorophyll), and zooplankton observed in zig-zag transects on 11 and 12 April showed a center of upwelling off Cabo Nazca and indicated remarkable spatial variability of all parameters. Distributions observed on 23 April were of interest because a relaxation of upwelling associated with reduced wind stress and the possible passage of a coastally trapped wave resulted in gross changes in oceanographic variables. Distribution and abundance of zooplankton species changed distinctly in the interval; phytoplankton concentrations decreased and temperatures increased. Higher numbers of zooplankton tended to occur on the downstream edges of phytoplankton concentrations, suggesting a chronology of events from upwelling to increased phytoplankton biomass to increased numbers of zooplankton. Estimates of grazing pressure of the zooplankton suggest that herbivores in the 0.35 to 2.0-mm spherical equivalent diameter range ingested about 40% of the daily production of phytoplankton.
|Original language||English (US)|
|Number of pages||20|
|Journal||Deep Sea Research Part A, Oceanographic Research Papers|
|State||Published - Jul 1983|
ASJC Scopus subject areas
- Environmental Science(all)
- Earth and Planetary Sciences(all)