There is a growing realisation that the widespread use and degradation of plastics has created a legacy of plastic pollution. Mass balance studies have suggested that a large proportion of release plastics waste may now be present as micro- nano-scale particles. There is little knowledge of the potential effect of these small polymer particles on organisms and ecosystems. Freshwater ecosystems are on the frontline since many of these nanoplastics will, through the sewage system, end up in freshwater habitats.
Laboratory feeding studies have shown that polymer particles are adsorbed by primary producers such as algae, ingested by a range of freshwater organisms, and transported through aquatic food chains to top consumers. The impact on freshwater organisms or ecosystem function is still poorly known, but there is some evidence that adsorption of polystyrene particles hinders algal photosynthesis and growth, and that as they travel through the foodchain they may also affect metabolism and behaviour.
However, to date, most laboratory experiments worked with concentrations of nanoplastics that are unrealistic in natural environments (>50mg/l compared to the 50ng/l found in rivers (e.g. Eriksen et al 2013), have been limited to gut or dead tissue analysis because nanoplastic identification methods are coarse.
Here we propose a real-world assessment of the fate of nanoplastics through freshwater ecosystems, through both lab and field experimentations. We will experiment with realistic concentrations of commercially available gold nanoparticles coated with a polystyrene shell. Polysterene is the 6th most common plastic used and cannot be recycled, which makes it a very relevant pollutant. To track the individual nanoplastics in sediments and live biota, we will use a four-wave mixing (FWM) imaging interferometry developed by supervisor Borri which is an efficient method to detect single small (<50nm) gold cored nanoplastics.
In controlled laboratory conditions, we will explore the rate of ingestion, excretion, cellular intrusion, survival and growth on: (i) the water flea Daphnia magna that will be collected and observed live under our FWM microscope at various time points after NP exposure, and (ii) several river biota including biofilm and primary consumers (e.g. Mayfly larvae). River biota are more difficult to culture but work will build on taxa and techniques that have already been successfully trialled at CEH and elsewhere.
In field experiments in our Llyn Brianne stream mesocosms in mid Wales will explore over several months the fate of these nanoplastics within: (i) the sediment and water column, with focus on potential aggregation and concentration at different depths, (ii) the biofilm, with focus on accumulation and adsorption by different components of the biofilm, and working on both stone and leaf biofilm, (iii) primary consumer invertebrates, with focus on accumulation but also on growth and population density compared to, and (iv) top predator invertebrates, to explore the pathways into organisms and through foodwebs.
The student will receive training from the supervisors in the design and sampling techniques linked to physiological and ecological experimentation both in the lab and in the field (Durance and Spurgeon group), as well as in state-of-the-art imaging technologies (Borri group).
The student will also be trained in analysis using the R package software and key imaging software.
The student will be part of the Water Research Institute Early Career Group that comprises more than 35 PhD and postdocs from across the natural and social sciences with a research project on a water challenge. This provides the student unique opportunity to work alongside and take part in regular interdisciplinary events and workshops on key water challenges.
Applicants must hold (or expect to hold) a biological degree at the 2:1 level or higher. A high level of competence in ecology is essential, and experience in freshwater bioscience would be a significant advantage, but not requisite since full training will be provided.
Open to UK and EU students. All EU applicants must have been ordinarily resident in the EU for at least 3 years prior to the start of their proposed programme of study.
Applicants from EU countries who do not meet the residency requirements may still be eligible for a fees-only award.
For information on how to apply for postgraduate study at Cardiff University, please follow this link: http://www.cardiff.ac.uk/study/postgraduate
The application deadline is 1600 hours GMT Monday 6 January 2020 and interviews will take place between 10 and 21 February 2020. For more information about the NERC GW4+ DTP, please visit https://nercgw4plus.ac.uk
Eriksen et al., 2013. Microplastic pollution in the surface waters of the Laurentian Great Lakes. Mar. Pollut. Bull. 77, 177–182.
Windsor, F.M., Durance, I., et al, S.J. 2019. A catchment-scale perspective of plastic pollution’, Global Change Biology, 25: 11207-1221.
Horton Alice A.; Vijver Martina G.; Lahive Elma; Spurgeon David J.; et al, 2018. Acute toxicity of organic pesticides to Daphnia magna is unchanged by co-exposure to polystyrene microplastics. Ecotoxicology and Environmental Safety, 166, 26-34
Borri, P.et al. 2019. Imaging and tracking single plasmonic nanoparticles in 3D background-free with four-wave mixing interferometry.
Plasmonics in Biology and Medicine XVI, Vol. 108940. Society of Photo-Optical Instrumentation Engineers (SPIE) pp. 34