ELSEVIER EcologicalEngineering 5 (1995) 445-468 ECOLOGICAL ENGINEERING Impacts of environmental scenarios on chlorophyll-a in the management of shallow, eutrophic lakes following biomanipulation: An application of a numerical model Mahesh Jayaweera *, Takashi Asaeda Department of Civil and Environmental Engineering, Saitama University, 255, Shimo-okubo, Urawa, Saitama 33, Japan Received 20 January 1995; revised 25 April 1995; accepted 1 May 1995 Abstract Accurate prediction of species changes in lake ecosystems following biomanipulation measures is of paramount importance in view of water quality management. The temporal variation of phytoplankton biomass as chlorophyll-a and transparency as Secchi depth measurements are studied in the Lake Bleiswijkse Zoom, The Netherlands, with a compre- hensive structural dynamic model. In the formulation of the biological model, phytoplank- ton as several species, zooplankton, detritus, planktivores and benthivores, and piscivores are considered to be major contributing state variables for the model. The primary goal of this paper is to describe the possible impacts of several environmental scenarios on chlorophyll-a biomass qualitatively as it would help lake and environmental managers and relevant authorities elucidate the processes of eutrophication and biomanipulation in a broad way. Some of the scenarios that have been studied by this model are: (1) The effect of fixed stoichiometry in terms of internal nitrogen and phosphorus that are tied up within algal cells; (2) the effects of external phosphorus limitation; (3) light limitation and external nitrogen limitation on algal growth; (4) probable consequences that have taken place within the chlorophyll-a biomass due to change in biomasses of various aquatic organisms; and (5) possible changes of chlorophyll-a biomass due to higher temperatures caused by global warming. Keywords: Chlorophyll-a; Eutrophic lakes; Biomanipulation; Numerical model; Lake ecosys- tems; Phytoplankton * Corresponding author. Elsevier Science B.V. SSDI 0925-8574(95)00020-8