What factors influence the species composition of phytoplankton in lakes of different trophic status?

The paper articulates some present concepts relating to the selection of phytoplankton along trophic gradients. Concerns over lake eutrophication have heightened the importance of nutrients but it is not obvious that interspecific differences in the nutrient requirements of algae genuinely segregate species except under chronic deficiencies. The selectivity supposedly generated by altered resource ratios is re-examined. It is argued that ratios explain very little of the distribution of species with respect to trophy. However, changing nutrient loading does have consequential impacts on the availability of other requirements including light and carbon dioxide. It is argued that the trophic spectrum is not a single dimension of a single factor but, rather, a template of factors covarying in consequence of the larger levels of biomass that are supported, and which weight in favour of the growth and survival prospects of particular kinds of planktonic algae. The trophic spectrum is a probabalistic outcome of several dimensions of variability.