Modelling phytoplankton dynamics in lakes and reservoirs: the problem of in-situ growth rates

During the Surface Water Acidification Programme, ahydrochemical plot study was carried out at thepristine Høylandet study site during 1986–89. Theplot soils were acidic iron podzols (sensuKubiena), with a significant content of secondaryaluminium (Al), forming a potential major source oftoxic Al in streams and lakes. Rain and mist inputscontain small amounts of anthropogenic sulphate, withammonium inputs being enhanced during the summermonths. Vegetation canopy interactions, includingsorption and leaching, change input water chemistrybefore it reaches the soil, in which organicinteractions increase, especially during the summer.Amphibole in the soil parent material is probablyresponsible for the large mineral weathering ratedetermined and this source of base cations, alliedwith the small anthropogenic inputs, results in Alconcentrations in the streamwater being small incomparison with impacted sites.