Fig. 4.
Response of phytoplankton communities to HHQ exposure. Difference in growth rate (d−1) in phytoplankton abundance after 24 h exposure to 410 μM (100 ng mL−1) 2-heptyl-4-quinolone (HHQ) compared to the DMSO control determined by chlorophyll a concentration, or flow cytometry counts of nano- and pico-eukaryotes (a) over eight experimental time points. Bars represent the mean (± s.d.) of biological triplicates and asterisks indicate significant changes in phytoplankton growth rate between the two treatments (p < 0.05). Ordination of eukaryotic phytoplankton communities based on 18S rRNA (b) and 16S chloroplast (c) amplicon sequence variants visualized by non-metric multidimensional scaling (NMDS) of Bray-Curtis distance. Circles and triangles correspond to DMSO control and HHQ exposed communities, respectively. Symbol color denotes experimental time point.