This proposal on "Evaluation of Critical Depth Hypothesis for Phytoplankton in Polar Waters" between Dr. Osmund Holm-Hansen of the Institute of Marine Resources, Scripps Institute of Oceanography, University of California at San Diego, and Dr. Egil Sakshaug of the Biological Station, University of Trondheim, Norway, is sponsored by NSF. Dr. Holm-Hansen proposes to spend two months primarily analyzing data he and Dr. Sakshaug have acquired in numerous cruises in both polar regions during the past seven years, as well as data both have produced in the laboratory which is essential to interpreting their field data. Their computerized data bases consist of simultaneously acquired information on physical-biological-optical characteristics in vertical profiles in the upper 200 m of the water column. The investigators wish to model the dynamic interaction between growth and physiology of the phytoplankton and the mean irradiance to which the cells are exposed as influenced by vertical mixing processes. They shall interpret data within the general framework of the Critical Depth hypothesis first described by Sverdrup in 1953, expecting that their large data base should provide a more realistic formulation of this concept.
