Investigating the impact of emerging human pollutants on marine Synechococcus

Pollution of the marine environment as a result of human activity is an issue of growing concern. Detection of pharmaceuticals and personal care products (PPCPs) in marine ecosystems is increasingly being reported and may adversely impact marine organisms. Toxicity testing of PPCP-related substances has focussed largely on model organisms with limited ecological relevance. I examined the impact of emerging pollutants on representative strains of Synechococcus, a highly abundant key marine primary producer. Synechococcus growth was tracked over 72 hrs using three independent techniques: optical density at 750nm, in vivo chlorophyll a fluorescence and autofluorescent cell counts by flow cytometry, to compare common cyanobacterial growth monitoring methods. Silver and zinc oxide nanoparticles significantly inhibited growth of all tested strains at concentrations above 5 mg/L and 0.01 mg/L respectively. For triclosan, concentrations above 0.1 mg/L were inhibitory to growth. Oxybenzone and ibuprofen had no significant impact on growth at concentrations up to 10 mg/L and 5 mg/L respectively. Oxygen production was significantly reduced in Synechococcus CC9311 on exposure to triclosan and silver nanoparticles,indicating these substances can impact photosynthesis. Synechococcus species showed higher sensitivity to zinc nanoparticles and lower sensitivity to the other tested compounds than reported fo rmost previously tested marine organisms, indicating the need to extend ecotoxicological testing of non-model organisms, particularly photosynthetic prokaryotes.