FACTORS CONTROLLING PRIMARY PRODUCTION IN LAKES AND RESERVOIRS: A PERSPECTIVE

ABSTRACT

Phytoplankton productivity and biomass fluctuations are controlled by the same energy and nutrient inputs and the same balance of gain and loss factors in natural and manmade lakes. However, some significant physical and hydrodynamic differences between lakes and reservoirs do exist which influence (1) the relative contributions of various primary producers to their food-webs, (2) the relative importance of certain limiting factors to primary production (e.g., turbidity, nutrient availability, flushing rate), (3) the spatial variability of primary production within reservoirs, and (4) the applicability of lake-based classifications and empirical relationships to reservoirs. An important distinction between most natural and manmade lakes is that reservoirs are semi-fluvial environments that fall between rivers and lakes on a continuum of aquatic ecosystems. A wider recognition of the riverine influences on reservoir ecosystems will enhance our understanding of the spatial and temporal heterogeneity associated with manmade impoundments and, thereby, permit more effective management of reservoir resources.