BEERS ET AL.: PLANKTON AND UPWELLING OFF PERU 



We are left with a system that is undoubtedly 

 the result of a combination of interacting factors 

 — both biological and physical — which can be 

 sorted out only semiquantitatively. Apparently 

 a loss equivalent to about 25 Cf of the phytoplank- 

 ton production may have been due to grazing 

 by zooplankters. As measured here, diffusive 

 mixing of the patches with adjacent waters and 

 sinking of the phytoplankton would account for 

 considerable additional loss of phytoplankton 

 material. In addition other avenues of possible 

 loss such as the direct consumption by the an- 

 chovies exist but were not evaluated here. That 

 the relative significance of the different variables 

 may change on a very small scale in time and 

 location at this time of year can be suggested. 

 Such complexity would lead to the variety of 

 conditions that have been described from the 

 coast of Peru. 



ACKNOWLEDGMENTS 



This study was stimulated by the interest and 

 earlier observations of the late Dr. John D. H. 

 Strickland and several other colleagues from the 

 Food Chain Research Group. Plans for the 

 present cruise were coordinated by Dr. Strick- 

 land, and he participated in this as Chief Scien- 

 tist until forced by illness to return home mid- 

 way during the project. His enthusiasm and 

 devotion to this and similar field studies of 

 marine food chains have been of great inspira- 

 tion to us. 



We are grateful to members of the staff of the 

 Instituto del Mar del Perii and, in particular, 

 0. Guillen, Dr. Romulo Jordan, and Sra. B. Rojas 

 de Mendiola, for their interest and aid in making 

 plans for the cruise. 



The work of Mrs. Freda M. H. Reid in the 

 phytoplankton taxonomic studies and Gene L. 

 Stewart for some of the microzooplankton 

 quantitative analyses are appreciatively ac- 

 knowledged. Nutrient analyses were carried out 

 by Miss Lucia Solorzano and chlorophyll a anal- 

 yses by J. B. Jordan aboard ship. Miss Betsy 

 Fuglister was responsible for the computer pro- 

 gramming of the data. Computational time pro- 

 vided by the Scripps Shipboard Computer group 

 is acknowledged with thanks. Assistance in the 



preparation of the calculation of dynamic topog- 

 raphy was provided by Miss Christine Dall. 



These studies were supported under AEC 

 Contract No. AT(11-1)GEN 10, P.A. 20 and 

 National Science Foundation (Oceanography 

 Section) Grant GB 12127. 



LITERATURE CITED 



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