The Intermediate Disturbance Hypothesis and Its Applicability to Planktonic Communities: Comments on the Views of Padisák and Wilson

The relevance of Connell’s Intermediate Disturbance Hypothesis (IDH) to explanations of diversity and co-existence among plant species generally and in the phytoplankton in particular has been debated recently. Compared to terrestrial vegetation, planktonic communities experience distorted time and space scales. Generation times are in the order of days, not years to decades. Advective fluid transport raises the critical patch size to the order of kilometers. Within these scales, species survival and growth, community assembly and successional development in the phytoplankton conform to all the standards (compositional, strategic, thermodynamic) of conventional community organisation. These processes are known to move toward competitively excluded outcomes. Equally, they are liable to be interrupted by externally imposed disturbances, which reset the succession or alter its potential outcome. These findings are not only illustrative of intermediate disturbance but are instructive in the nature of diversity-disturbance relationships generally. IDH has considerable potential to explaining persistent species co-existence.