Marine microbial communities demonstrate resilience to engineered silver nanoparticles

Silver nanoparticles (AgNPs) are effective antimicrobial agents that are increasingly exploited in a range of consumer products, yet their risk to ecologically important marine microbial communities is uncertain. Ammonia oxidising bacteria (AOB) and archaea (AOA) are important for ecosystem function in the ocean, where low nitrogen availability is often a limiting factor for primary productivity. This study aimed to determine the effect of a pulse addition of methoxypolyethylene glycol capped (c)AgNPs, uncoated (u)AgNPs, and Ag2SO4 on seawater and marine sediment microbial communities, particularly (AOB) and (AOA). Bacterial and archaeal 16S rRNA genes, AOB and AOA ammonia monooxygenase (amoA) gene abundances were measured by qPCR both before Ag addition and following five days exposure, . Marine microbial communities demonstrated resilience to up to 5 mg L-1 uAgNPs, cAgNPs and Ag2SO4, whereby gene abundances were not significantly impacted over five days by any of the Ag treatments and remained at x copies/ g dry weight etc. Indeed, seawater bacterial and archaeal 16S rRNA gene abundances even increased significantly following exposure to 0.05 mg L-1 cAgNPs and Ag2SO4. In conclusion, all forms of Ag exposure had no impact on gene abundance or community profiles of entire bacterial and archaeal communities in seawater and marine sediments. Ag toxicity may be mitigated by the physicochemical properties of seawater, and our results provide a promising outlook for marine microbial communities exposed to AgNPs at current and future predicted concentrations.