Illustration of the chaining effect. Both figures display the same scatter plot of sample 180912_PM_PEL_B13 (high tide, pelagic, summer, Bouée 13), where one dot is a read (there are 37036 dots), with the first MDS component on the x axis and the second one on the y axis. The two plots differ by the way dots are coloured. In the left plot, dots are coloured according to the OTU they belong to. In the right plot, they are coloured according to the species they have been assigned to. Only the species and OTUs with the 12 largest sizes have been coloured; the remaining ones are coloured in grey (if not, many colours would have been indistinguishable).