The overall aim of this project is to establish the behaviour, fate and ecotoxicological effects of silver nanoparticles (AgNPs) in estuarine and coastal waters. Silver is a toxic element and increasingly used in NPs added to consumer products. This is resulting in AgNP release to marine waters. There is a lack of knowledge on AgNPs in marine systems, hampering development of legislation. The project has the following specific objectives:1.Manufacture AgNPs with different core sizes and coatings and establish their dissolution, surface properties and behaviour under different environmental conditions: Ag salts will be used to manufacture AgNPs and stable isotope 109AgNPs by chemical reduction using selected chemical agents2.Determine speciation of AgNPs in seawaters: Experiments will be conducted by spiking solutions with manufactured AgNPs of different chemical characteristics to study Ag ion release, kinetics of AgNP dissolution, solubility, shape and size changes of AgNPs. Furthermore, we will determine the concentration of AgNPs present in estuarine and coastal waters3.Study the toxic effects of AgNPs on marine organisms: We will undertake toxicological studies using phytoplankton and oyster embryo larvae. Experiments will be carried out by varying the AgNPs dose, exposure time and toxicological media.4.Establish a model of behaviour and fate of AgNPs in marine environments: The obtained data will be used for the development of mathematical models aimed to model the residence times, dynamic concentration profiles and aggregate size distributions of AgNPs in seawatersThe obtained results will address vital questions: Are AgNPs already present in EU seawaters? Can AgNPs be bioavailable in marine ecosystems? What is their speciation and toxicity in marine waters? Can a model describe the fate and behaviour of AgNPs in solution?We will communicate the outcomes of this project to the scientific community, the wider public, and also to policy makers (CEFAS, UK)