- In Lake Constance, phytoplankton productivity, together with parameters relevant for the production process, was assessed year-round at about 500 dates between 1980 and 1995/1996. During this period, the concentration of total phosphorus during winter circulation decreased from more than 80 to 22 ;g/l as a consequence of sewage diversion and waste water treatment within the catchment area. By contrast, annual photosynthetic rates remained virtually unchanged for about 10 more years following phosphorus decline (mean value 288 " 21 g C m-2 a-1), and thereafter decreased only by about 25 % until 1996. The aim of this study is to analyze factors responsible for this pronounced resilience.
