Water colour, phosphorus and alkalinity are the major determinants of the dominant phytoplankton species in European lakes

Analysis of phytoplankton data from about 1,500 lakes in 20 European countries has revealed that two-thirds of the species that dominate lakes during the summer are dominant right across Europe. Using Canonical Correspondence Analyses, we have examined how both habitat conditions within lakes and environmental factors over broad geographical scales explained the distribution of the 151 most common summer dominant species. The distributions of these species were best explained by water colour and latitude, although alkalinity and total phosphorus also appeared to be important explanatory factors. Contrary to our original hypothesis, summer water temperatures had a negligible impact on the distribution of dominants, although, due to the restricted summer season we examined, only a limited temperature gradient was present in the dataset. Cryptophytes occurred more frequently among dominants in Northern Europe whereas cyanobacteria and dinophytes dominated more in Central and Southern Europe. Our analyses suggest that besides nutrient concentrations, other water chemistry variables, such as alkalinity and the content of humic substances, have at least as important a role in determining the distribution of the dominant phytoplankton species in European lakes

Phytoplankton in the physical environment: beyond nutrients, at the end, there is some light

This article summarizes the outcomes of the 15th Workshop of the International Association for Phytoplankton Taxonomy and Ecology. Four major issues dealing with the role of physical factors in phytoplankton ecology were addressed in the articles of this special volume: global change and its likely impacts on phytoplankton, the role of physical factors in the autecology of particular species, impacts on the inocula for the following years, and the role of light in shaping phytoplankton dynamics. Case studies from different types of aquatic environments (rivers, deep and shallow lakes, floodplain lakes, wetlands, oxbows, and even the deep ocean) and from diverse geographical locations (not only from the Mediterranean and temperate regions, but also from subtropical and tropical ones) have shown that physical forcing exerts a variety of selective pressures with impacts ranging from molding shape and size of organisms to modifying, through cascade effects, the structure of whole ecosystems