Phytoplankton (unicellular algae) is the fundamental source of life in the sea. This perception was established more than one-hundred years ago by the German Victor Hensen (1835-1924), physiologist at the University of Kiel. He was especially interested to quantify the productivity of fishing areas. The first step was to catch plankton and he started with a modified butterfly net. Then, he organized simultaneous catches by ships of different organizations in northern Germany, which were coordinated on a national level by the Kiel Commission since 1870 and later internationally by the International Council for the Exploration of the Sea (ICES), founded in 1902. The results of these investigations in the following decades brought the understanding of how the food web/metabolism functions in the sea and how it is influenced by certain factors – physical, chemical and biological.

Whereas limnologists did understand these processes already in the late 19th century, marine plankton modeling started only in the midst of the 20th by G.A. Riley (1911-1985), director of the Institute of Oceanography at Dalhousie University/Halifax, together with the physical oceanographer H. Stommel (1920-1992) of Woods Hole Oceanographic Institution and followed by the mathematician J.H. Steele of Aberdeen’s Marine Laboratory.

1970, in the frame of a multidisciplinary marine research program at the University of Hamburg a project was initiated to develop applications of hydro-numerical methods for quantitative reproduction and prediction of physical-chemical-biological processes in the sea. In order to get ground-truth data, a 100 days data set was collected by an international and multidisciplinary experiment, which was conducted 1976 at the Fladenground in the northern North See, called FLEX’76. The crucial results will be presented.

This presentation is based on work co-authored by Guenther Radach.