Figure 3.

Drivers of Plankton Diversity in the Surface Ocean

(A) Correlation of contextual variables (abiotic and population densities, x axis) with the Shannon index of each MPG (y axis). The color gradient corresponds to the values of the Spearman ρ correlation coefficient and the dot size to their absolute value. The labels of the x axis are ordered according to a hierarchical clustering analysis of absolute Spearman ρ correlation coefficient values between each pair of contextual variables, whose corresponding dendrogram is shown in the top part of the plot. Yellow leaves correspond to the four variables analyzed in (B) and (C), also underlined below. Variables that do not cluster above the dotted line (|Spearman’s ρ| < 0.6) are considered as non-collinear. Percentages of pico, nano, and micro refer to the relative abundances of fractions of phytoplankton based on pigment analysis. Bacteria and picoeukaryote abundances were determined by FC, whereas imaging abundances refer to counts of individuals caught by nets (STAR Methods). MLD: mixed-layer depth. See also Figure S8.

(B and C) Individual explained deviance (color gradient and dot size) of four variables (B; Figure S9) and additive contribution of the same four variables to the total explained deviance in GAMs, with the Shannon index as a response variable (C; STAR Methods; Tables S1D and S1E).

In (A) and (B), non-significant coefficients or effects are not shown. In (C), significant effects are indicated by asterisks. MPG labels are always ordered according to a hierarchical clustering analysis after a Spearman correlation analysis based on the displayed values in each case (A–C).