The effect of silver nanoparticles on the prokaryote and eukaryote microbial community in the coastal eastern Mediterranean Sea

The release of nanosized particles of silver into the marine environment is of growing concern, as the impacts on marine life are not fully understood. Despite previous experiments that have proved the toxic effects of silver nanoparticles on plankton and photosynthetic organisms, the effect of Ag nanoparticles on important biogeochemical processes such as marine nitrogen fixation is still unexplored. Nine mesocosm enclosures were set up in Crete (Greece) for 12 days during May 2019. Three mesocosm bags were left unamended at ambient light and temperature, and the remainder manipulated with Ag nanoparticles and Ag addition (50 ng/L per day). With the aim of investigating both the diazotrophic and the whole community composition during the mesocosm experiment, seawater from each treatment was collected into 3 L bottles on day 0 and then on alternate days from day 1 to day 11. Seawater from each bottle was filtered onto Sterivex filters and DNA extraction carried out using the Qiagen AllPrep DNA/RNA mini kit. For prokaryotes, the 16S rRNA gene V4 PCR primer pair 515R and 806R was used. For eukaryotes, the 18S rRNA gene V9 PCR primer pair Euk1391F and EukBr was used.