Metatranscriptome profiling and 18S rDNA (V4) metabarcoding of salinity-induced sexualized phytoplankton of the Scheldt river (Belgium)

A natural phytoplankton sample was collected from the freshwater zone of the tidal Scheldt river near the city of Ghent (51°00'15.6"N 3°48'19.3"E) on 20/05/2022. The sample was filtered through a plankton net with a mesh size of 10 µm to concentrate the plankton and distributed over large 150-mL culture flasks. Part of the cultures were brought to a salinity of 10 parts per thousand (ppt) in order to induce sexual reproduction of certain centric diatom species. After 24h and 48h, two salt-treated and one control samples were harvested by filtration and flash frozen in liquid nitrogen. Deep metatranscriptome sequencing of total mRNA was performed on a NovaSeq 6000 S4 platform (150bp paired-end) and a de novo transcriptome was assembled with rnaSPAdes.