Nutrient growth conditions for Oscillatoria spp. and diatoms in two Norwegian lakes

Abstract

and diatoms in two Norwegian lakes. -Nord. y. . IS"N 0307-055x.The growth conditions and development of Asrerionellu formosa Hass., 7uhelluriu f&zesirutu (Lyngb.) Kutz.. Frugiluria croionensis Kitt., and Oscillutoriu spp. have been studied in Lake Vansje and Lake Mjma for many years. Some batch culture experiments have been performed with dilute phytoplankton populations in filtered water samples to support the field data. The results indicate that the concentrations of phosphate, nitrate, silicate o r chelators/Fe were important factors regulating the spatial and temporal distribution of the populations. Based on the assumption that the growth rates were strongly dependent on the external nutrient concentration, S, the growth conditions were divided into three types. The nutrient concentration may be too low to support growth, i.e. the growth rate k 5 0, or the population is nutrient growth limited (0 < k < kn,) or not growth limited, i.e. the population has maximum growth rate (k,,,). The nutrient concentration may be population density dependent, i.e. resource competition niay occur. or density independent separately or in combination. The growth strategies of the populations in the two lakes were partly explained by studying the nutrient growth conditions of the populations. K. Bj~rndulen. Fylkesmunnen i Ostfold,