title: Impact of silver nanoparticles on marine diatom Skeletonema costatum.
abstract: When silver nanoparticles (AgNPs) are used commercially at a large scale, they infiltrate the environment at a rapid pace. However, the impact of large quantities of AgNPs on aquatic ecosystems is still largely unknown. In aquatic ecosystems, the phytoplanktons have a vital ecological function and, therefore, the potential impact of AgNPs on the microalgae community has elicited substantial concern. Therefore, in this study, the impacts of AgNPs on a marine diatom, the Skeletonema costatum, are investigated, with a focus on their photosynthesis and associated mechanisms. Exposure to AgNPs at a concentration of 0.5 mg l(-1) significantly induces excess intracellular reactive oxygen species (ROS, 122%) and reduces 28% of their cell viability. More importantly, exposure to AgNPs reduces the algal chlorophyll-a content. Scanning electron microscopy (SEM) was conducted, which revealed that AgNPs obstruct the light absorption of algae because they adhere to their surface. The maximum photochemical efficiency of photosystem II (Fv/Fm) demonstrates that exposure to AgNPs significantly inhibits the conversion of light energy into photosynthetic electron transport. Moreover, the genes of the photosystem II reaction center protein (D1) are significantly down-regulated (P < 0.05) upon exposure to 5 mg l(-1) AgNPs. These results suggest that the physical adhesion and effects of shading of AgNPs on algae might affect their light energy delivery system and damage the crucial protein function of PSII. The photosynthesis inhibition effect of AgNPs is largely different from Ag(+) . This study shows that AgNPs at higher concentrations might have serious consequences for the succession of the phytoplankton communities and aquatic ecosystem equilibrium. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, China.|City University of Hong Kong Shenzhen Research Institute, Shenzhen, 518057, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, China.|City University of Hong Kong Shenzhen Research Institute, Shenzhen, 518057, China.|Environmental Science Programs, School of Science, Hong Kong University of Science and Technology, Clear Water bay, Kowloon, Hong Kong, China.
authors.forename: Jinping
authors.initials: J
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, China.|City University of Hong Kong Shenzhen Research Institute, Shenzhen, 518057, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yi
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D017377:Diatoms / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D015536:Down-Regulation; D015870:Gene Expression / Q000187:drug effects; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D010316:Particle Size; D010788:Photosynthesis / Q000187:drug effects; D045332:Photosystem II Protein Complex / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D012834:Silver / Q000737:chemistry / Q000633:toxicity*; D013499:Surface Properties; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity*
chemical_list: D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D012834:Silver; D000077194:Chlorophyll A
keywords: cell viability; chlorophyll-a; marine microalgae; nanotoxicity; oxidative damage; photosynthesis; silver ion; silver nanoparticles