Light limitation of primary production in high latitude reservoirs

J. Sahlberg (1) , L. Rahm (2)

1 SMHI - Swedish Meteorological and Hydrological Institute
2 Department of Water and Environmental Studies

To explore the effects of vertical mixing on the primary production in a northern reservoir, a Lagrangian particle dispersion model was coupled to a 1-D reservoir model where the vertical mixing was calculated using a k-? model together with an empirically-based deep-water eddy viscosity. The primary production of each phytoplankton cell is assumed to be a function of the ambient light and not to be nutrient limited. The photoadaption follows first-order kinetics where the photoadaptive variables, a, b, and P_m, describe the coefficients of the photosynthesis-irradiance curve. The model is applied to the northern reservoir Akkajaure, which is strongly regulated with a mean and maximum depth of 30 m and 100 m respectively. Based on the release of 1000 particles (plankton), the model calculated the mean primary production of each plankton, during four different growing seasons. Vertical mixing has a substantial effect on the vertical distribution of phytoplankton and, thus, on the primary production in a reservoir. It was found that primary production was greater in a cold summer with weak stratification than in a warm summer when the reservoir was more stratified.

Domaines: Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

J. Sahlberg, L. Rahm. Light limitation of primary production in high latitude reservoirs. Hydrology and Earth System Sciences Discussions, 2005, 9 (6), pp.707-720. ⟨hal-00304887⟩