The intermediate, disturbance hypothesis - species diversity or functionaldiversity?

Phytoplankton dynamics in a shallow eutrophic take were investigated over a 3 year period with respect to environmental forces which drive species com position and diversity. Diversify was calculated on the basis of species as well as on the basis of their functional properties (the C-R-S concept). S tratification and water column mixing had a strong impact on phytoplankton composition. Application of a similarity-diversity, model revealed that a h igh diversity was a transient non-stable state, whereas drastic changes or lon-a-lasting stable environmental conditions are characterized by low dive rsity. This effect was more pronounced when the diversity, was calculated o n the basis of the phytoplankton species' functional properties. Thus, this functional approach supports the intermediate disturbance hypothesis from field data.