Experimentelle Überprüfung der "Intermediate Disturbance Hypothesis" (Connell 1978) an Modell-Lebensgemeinschaften planktischer Bakterienisolate

The general applicability of two aspects of the "Intermediate Disturbance Hypothesis" (IDH), the unimodal relationship between species diversity and the disturbance regime with maximum diversity resulting from intermediate disturbance frequency, and the disturbance induced pattern of functional organism types, were tested experimentally. Model communities of 14 natural bacterioplankton isolates cultured in chemostats were 'disturbed' by pulsed supply of a limiting resource with varying pulse interval lengths. The isolates were characterised by molecular techniques and functionally grouped into guilds regarding the strain specific maximal growth rate. Methods to monitor changes in bacterial diversity were agar plate counts and flowcytometer counts of strain specifically immunofluorecence labelled cells. The IDH was confirmed regarding the temporal disturbance diversity pattern at the end of the experiment for both enumeration approaches (maximum diversity at disturbance intervals of ca. 2 generation times). Also the observed functional patterns regarding specific growth speed strategies were consistent to those predicted by the IDH.