DISTRIBUTION OF BIOLOGICAL-ACTIVITY IN THE LOWER ST-LAWRENCE ESTUARY AS DETERMINED BY MULTIVARIATE-ANALYSIS

Three stations located in the Laurentian Trough were investigated thre e times during the summer production maximum (in June-July 1990; COUPP BBO-1 cruise). A range of multivariate analyses was carried out to ext ract major physical-biological features in a large data set covering t he whole cruise. This study presents the advantages of combining conve ntional principal component analysis (PCA) with a three-way data analy sis. PCA provides the centre of gravity of the different locations for each variable and each sample during the cruise without temporal info rmation. Three-way data analysis produces the trajectory of the differ ent site/time locations for each variable and each sample, and clarifi es spatial and temporal relationships between variables. The results r eproduce the main patterns of the lower St Lawrence Estuary during the summer plankton bloom and indicate an upstream movement of warm and l ess saline waters associated with surface production. Apparently these large changes at the surface are not reflected in the deeper layers. Cluster analysis suggests that autotrophic and heterotrophic activitie s are decoupled when production is low and are correlated only when pr oduction increases.