design: Water samples were filtered through using the 0.22 micrometer filters tp collect phytoplankton and DNA was extracted from the trapped cells using MagAttract PowerWater DNA/RNA kits (Qiagen). DNA was sent in 20 microliter volume to Iowa State University DNA Facility for amplicon-sequencing of the 18S rRNA gene. We selected the 1391F-EukBr primers from the Earth Microbiome Project to target the V9 region of the 18S rRNA gene, 2x250 bp chemistry.