21 refs

New Zealand's climate allows for some cyanobacterial growth in winter. Globally this is uncommon. Fluctuations in growth are much related to transitory weather conditions. Most lakes in New Zealand have the potential to grow undesirable amounts of cyanobacteria, given sufficient nutrient inputs to support a large biomass whether cyanobacterial or not. After extreme dominance has been attained, cyanobacterial populations redefine the light and hydrodynamic environment sufficiently to need only maintenance growth to exclude any competing species. Quantifiable lake conditions of light, hydrodynamic stability, and buoyancy regulation can largely explain the occurrence of cyanobacterial blooms in general, without recourse to other details of the environment, but further ecologicaly details are required to explain the occurrence of a particular species as distinct from a class of cyanobacteria. Stimulation of one species over another is likely to be due to brief combinations of conditions, constituting an 'event' disconnected from other events