Modeling bio-geochemical interactions in the surface waters of the Gulf of Trieste by three-way principal component analysis (PCA) Original Research Article

Data of temperature, salinity, dissolved oxygen, nutrients and chlorophyll measured on samples of surface seawater and collected monthly during 2 years in different sites of the Gulf of Trieste are modeled by means of three-way principal component analysis (PCA). Missing values are handled using an expectation maximization algorithm, regression or substitution with random numbers, depending on their origin. Physicochemical parameters are described by three different components that explain the effect of the river input on the seawater pattern, the effect of temperature, and metabolic–catabolic activity of the phytoplankton, respectively. One spatial component accounts for the gradient of influence of the estuarine waters in the Gulf, and three temporal components characterize three main seasonal conditions. Anomalous situations, generated by meteoclimatic events, are highlighted.