Figure 7
Cluster analysis of picophytoplankton communities along the salinity gradient. The analysis was performed on the log (abundance + 1) data matrix. The x-axis shows station from S1 to S20. Two main groups of stations were discriminated based on their population richness: high richness (white, >4 populations) for salinity <3.5% where the seven different sub-populations were identified (P-Eu1, P-Eu2, P-Eu3, P-Eu4, P-Eu5, Synechococcus-like and Prochlorococcus-like), and low richness for salinity >3.5% (grey, ≤ 4 populations). In this latter group, two sub-groups of stations where discriminated based on their population composition: a sub-group characterized by a great dominance of pico-eukaryotes (>93%) for salinity ranging between 3.5 and 14.0%, and a sub-group where only Prochlorococcus-like and P-Eu1 occurred for salinity greater than 14.0%.