A three year survey of the aquatic vegetation of a New Zealand dune lake is described. Pukepuke Lagoon is a shallow (max. depth 85cm.), slightly saline lagoon with 15ha of open water. Its inflows drain intensively farmed land and are rich in nutrients, especially phosphorus. Dense macrophyte crops characterised the lagoon each spring but the component species differed each year.
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.
The 'Intermediate Disturbance Hypothesis' (IDH) is one mechanism suggested to explain indefinite species coexistence. Hutchinson's original concept of the IDH was of a mechanism based on patch dynamics, and logical consideration shows that IDH works only if interpreted this way. Dependence on patch dynamics distinguishes IDH from Gradual Climate Change (GCC), though they are distinct also in terms of premature death of individuals, species selectivity, and the suddenness and transience of the perturbation.