PLS and PCR methods in the assessment of coastal water quality

Partial least squares regression analysis (PLS) and principal component reg ression analysis (PCR) were examined as methodological procedures for asses sing the quality of coastal waters in a tourist area. Four variables relate d to the trophic state of waters, namely nitrate, nitrite, ammonia and phos phate were analyzed. The models resulting from PLS and PCR were very simila r. Both defined three groups of water masses characterized by different nut rient loadings. These groups were in accordance with those obtained by nume rical classification. The PLS method was selected as the optimal model, on the basis of its lower prediction errors (lower Press and Rmsd values). For management purposes, this statistical model allows mesotrophic conditions, reflecting some nutrient enrichment over background conditions, to be char acterized and the successful diagnosis of additional samples within this co ntext.