Mesocosm experiments conducted during Heincke cruise HE425 in 2014. Sea water samples were taken at two stations in the North Sea to inoculate two mesocosms which were subsequently induced using algal exudates. Approx. 100 mL of Seawater were taken every two days for 10 days in total and harvested using 0.2um PC filter. Genomic DNA and RNA were extracted from the filters using acidic phenol. RNA was converted to cDNA. DNA and cDNA were subjected to PCR targeting the bacterial 16S rRNA gene. Sequencing was performed using the Illumina MiSeq system.