Size matters: how does microplastic and nanoplastic size influence their abundance and toxicity in the aquatic environment?

Prof Richard Lampitt, Dr Alice Horton, Prof Andy Cundy, Dr Cael Barry, Dr Katsiaryna Pabortsava

Microplastics (1 µm - 5 mm plastic particles) are a ubiquitous and persistent pollutant found globally throughout the environment. Research on plastic pollution has accelerated in recent years, although many questions still remain. Although usually derived from land, a vast amount of microplastics enter rivers and the ocean, environments which host important aquatic ecosystems. With degradation and fragmentation of these particles in the environment, increasing numbers of smaller particles are formed, even forming nanoplastics (< 1 µm). Environmental studies regularly report a comparatively higher abundance of smaller particles. However, at the smallest sizes (< 10 µm), detection and analysis remain challenging. It is understood that the smallest microplastics are likely to be the most harmful, due to their high bioavailability and ability to cross cell membranes. Therefore, it is critical that we understand the abundance, fate and behaviour of these particles, in addition to understanding how size can influence toxicity. A combination of fieldwork, laboratory analysis, experimental studies and statistical modelling will be used in this project to enable a thorough investigation of microplastics and nanoplastics within estuarine and marine environments, including Southampton Water, the Solent and the Atlantic Ocean.


This PhD project will investigate the relationship between plastic particle size, abundance, behaviour and hazard. This project will utilise a range of skills and techniques including field sample collection and processing (involving sample collection cruises to the Porcupine Abyssal Plain (North Atlantic) open ocean observatory, in addition to analysis of existing marine water and sediment samples) and optimization of novel µFTIR spectroscopic and TOF-mass spectrometric techniques. Statistical modelling will assess provide uncertainty-quantified best estimates of environmental abundances of the smallest microplastics and nanoplastics that cannot currently be detected. Further, experimental ecotoxicology studies will be carried out using radio-labelled particles, to enable tracing and quantification of micro/nanoplastic bioaccumulation within tissues.



1.    How can existing data on microplastics size distribution enable us to better predict the abundance of the smallest micro/nanoplastic particles, where such data are not yet available?

2.    As degradation leads to particles becoming smaller, yet more numerous, how do the proportional differences in particle sizes and abundances vary depending on location and proximity to sources (e.g. estuarine vs open ocean)?

How does size influence particle ecotoxicity and bioaccumulation through translocation into organism tissues, especially key lower trophic invertebrates such as Daphnia magna (freshwater) and Calanus helgolandicus (marine)?

NOC, Southampton

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the National Oceanography Centre. Specific training will include:

  • Field survey design and sample collection (including training in inland and offshore sampling techniques)
  •  Sample processing and analysis, using state-of-the-art spectroscopic and spectrometric imaging and analysis techniques
  • Image processing techniques
  • Training in handling radiolabelled materials at the National Nuclear Users Facility NNUF-EXACT (University of Southampton/NOCS)
  • Organism culturing and ecotoxicology testing
  • Introduction to state-of-the-art statistical modelling techniques used in a wide variety of scientific disciplines.
Eligibility & Funding Details: 

Please see for details.

Background Reading: 
  1. Horton, A.A., Svendsen, C., Williams, R.J., Spurgeon, D.J. and Lahive, E., 2017. Large microplastic particles in sediments of tributaries of the River Thames, UK–Abundance, sources and methods for effective quantification. Marine pollution bulletin, 114(1), pp.218-226.
  2. Jeong, C.B., Won, E.J., Kang, H.M., Lee, M.C., Hwang, D.S., Hwang, U.K., Zhou, B., Souissi, S., Lee, S.J. and Lee, J.S., 2016. Microplastic size-dependent toxicity, oxidative stress induction, and p-JNK and p-p38 activation in the monogonont rotifer (Brachionus koreanus). Environmental science & technology, 50(16), pp.8849-8857.
  3. Pabortsava, K. and Lampitt, R. 2020. High concentrations of plastic hidden beneath the surface of the Atlantic Ocean. Nature Communications, 11, 4073.