ABSTRACT

ABSTRACT: Under European Commission project harmful algal bloom expert system (HABES), a rule based model has been developed in the Dutch pilot study for modelling Phaeocystis globosa (P. globosa) blooms in the Dutch coastal waters (Noordwijk 10) of the North Sea. The model uses decision trees to qualitatively predict bloom timing (bloom or not bloom in a certain week) and uses nonlinear piecewise regression to predict bloom intensity (cell concentrations) on the basis of available meteorological data. A multi-variable regression model was also set up to predict bloom duration if it is forecasted to take place. The constructed model clearly indicates that the joint effects of mean water column irradiance of mixing depth (Im), temperature (T ) and dissolved inorganic phosphorus (DIP) determine bloom timing and intensity. The bloom duration depends on the bloom timing (starting day), starting intensity and temperature. Irradiance is seen to act just as one of the triggers to P. globosa bloom. As long as it is higher than the threshold, extra irradiance plays little role in bloom intensity or duration. River discharge from the Rhine does not have instant effect on the bloom. The threshold values of Im, T and DIP independently found by the model are in accordance with those discovered by other researchers through laboratory experiments. The model was tested by an independent dataset from the same area, and the model results agree well with the real observations both qualitatively and quantitatively. The developed rule-based model is sensible to be physically interpreted from ecological aspects and is applicable in practice.