Results of the two-step fourth corner analysis (Pearson’s correlation coefficients) performed on Cytobuoy-derived phytoplankton traits and environmental variables.

Significant correlations at p>0.05 are highlighted in bold (n = 22-groups × 15-sites × 15-traits). Corresponding p-values are reported in Table S3.
aFirst principal component of all traits, aggregated representation of phytoplankton morphology (see Table S1);
bLength by SWS, the most accurate measure of particle length;
cTotal FL (integrated signal),
dMaximum amplitude of FL;
eFill factor, between 0 and 1, gives information on how the signal resembles a square signal, i.e. very low values indicate that the signal is concentrated in a very narrow peak, indicative of an uneven distribution of pigments within cell/colony;
fnumber of humps in the signal, proportional to number of cells for colonial phytoplankton or the number of FL peaks per particle.