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

Data of temperature, salinity, dissolved oxygen, nutrients and chlorophyll measured on samples of surface seawater and collected monthly during 2 year s in different sites of the Gulf of Trieste are modeled by means of three-w ay 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 describe d 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 account s for the gradient of influence of the estuarine waters in the Gulf, and th ree temporal components characterize three main seasonal conditions. Anomal ous situations, generated by meteoclimatic events, are highlighted. (C) 199 9 Elsevier Science B,V, All rights reserved.