Southern Ocean Microplastic Flux: Ecosystem and Carbon Impacts

Plastic pollution has become a global environmental issue, reaching even the most pristine and remote wildernesses of our planet, such as the Southern Ocean (SO). This region plays a major role in global oceanic circulation and provides fundamental ecosystem services to our planet, being responsible for 40% of the global atmospheric carbon uptake. Being well adapted to extreme but stable environmental conditions, Antarctic species are considered more vulnerable to environmental perturbations and pollutants, compared to species from lower latitudes. Thus, plastic pollution poses a serious threat to SO marine biota. Microplastics (< 5mm) will likely pose a greater environmental hazard as particles become more available for ingestion, with an increase in surface area facilitating chemical and biological interactions. However, the ways in which microplastics are transported to the deep ocean are still largely unknown. Understanding the fate of microplastic and quantifying the scale of the problem are necessary in order to minimize the environmental risks to and impacts on this unique biodiversity. The focus of this project is to investigate the main biological driver promoting the vertical fluxes of microplastics within the water column in a region of the Southern Ocean, to assess the influence of microplastic on marine ecosystem and biogeochemical cycle. The project is in the frame of CUPIDO project (https://www.bas.ac.uk/project/cupido/) that aims to quantify the impact of microplastic pollution on the ability of the ocean to uptake and transport atmospheric carbon in the oceanic sediment.

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Archived material from three key time-series sites located in the Southern Ocean will provide an existing sample set (BAS SCOOBIES programme) for new state of the art analysis. Samples have been collected by using moored and floating sediment traps. This will be combined with hydrological and biogeochemical data from oceanographic sensors. Microplastic and zooplankton samples analysis will be performed at BAS while biogeochemistry samples will be investigated at the University of Durham and St. Andrews. More detailed analyses to identify microplastic polymers will be done in collaboration with the Environmental Department at Siena University in Italy. There may be the opportunities to undertake fieldwork in the Southern Ocean as part of a BAS long-term SCOOBIES observation programme.

Project Timeline

Year 1

Working on literature review of project topic (contributing to Chapter 1 introduction)

Quantify the magnitude and seasonal variability of microplastics flux (Chapter 2 results).
Long term moored sediment trap samples deployed on a deep oceanic moored (>2000 m) platform will be analysed to quantify plastic amount, size, characteristics and seasonal trend. The characteristics of microplastic polymers will be performed by Scanning Electron Microscope and a combination of Raman and FT-IR (Fourier-transform infrared) spectroscopy techniques. FT-IR and Raman analyses will be performed respectively at BAS and at a collaborator institute in Italy (Siena University).

Year 2

Determine plastic export- and attenuation through the water column (Chapters 3).
The rates of microplastic vertical transport will be quantified through calculating the difference between plastic fluxes at different depths (up 400m). The student will investigate archived samples of short-term deployments floating sediment traps (24 hours) to provide a high degree of vertical resolution in the high productivity season. To quantify vertical variability in plastic sinking rates the student will carry out incubation experiments where identified plastic from the samples will be incubated within manipulated sea water to simulate variability in hydrological conditions (e.g. T, S). Polymers will be identified as for task in Year 1. Attendance of national Scientific meeting.

Year 3

Identify the role of zooplankton component in promoting the flux of microplastic (Chapter 4 results).
The student will quantify the amount of microplastic incorporated in faecal pellets (zooplankton faces) and zooplankton carcasses collected within the floating and moored sediment trap to assess the ratio of plastic: carbon with respect to flux and export. POC (Particulate Organic Carbon) and zooplankton biomass will be analysed using a CHN (Carbon, Hydrogen, and Nitrogen) auto-analyser (Durham University). The amount of plastic mass in the zooplankton components will be investigate using enzymatic digestion and techniques (BAS). Attendance of national Scientific meeting.

Year 3.5

Completion of thesis, high-level synthesis of project conclusions (Chapter 5 synthesis). Attendance of international scientific meeting.

& Skills

The IAPETUS 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 Durham and hosted at British Antarctic Survey (BAS). The student will join the Ecosystems group at BAS, and learn about Southern Ocean carbon cycle and zooplankton ecology and they will be part of CUPIDO team. Specific training will include a number of laboratory skills such as: sample preparation, clean laboratory chemistry, zooplankton/microplastic identification using light and scanning electron microscopy, and spectroscopy technique and biogeochemistry element analyser. The student will learn to work with floating and moored sediment traps and a set of oceanographic sensors. Presentation of results will be an important part of the training and will be both to the public and to scientific colleagues at conferences. If fieldwork is undertaken, this will include at-sea survival training course.

References & further reading

• CUPIDO project: https://www.bas.ac.uk/project/cupido
• BAS SCOOBIES program https://www.bas.ac.uk/project/scoobies/

• Rowlands, Emily, Galloway, Tamara, Manno, Clara . (2021) A Polar outlook: Potential interactions of micro-and nano-plastic with other anthropogenic stressors. Science of the Total Environment, 754. 12 pp. 10.1016/j.scitotenv.2020.142379
• Manno, C. , Fielding, S. , Stowasser, G. , Murphy, E.J. , Thorpe, S.E. , Tarling, G.A. (2020) Continuous moulting by Antarctic krill drives major pulses of carbon export in the north Scotia Sea, Southern Ocean. Nature Communications, 11. 8 pp. 10.1038/s41467-020-19956-7
• Bergami, E., Manno, C. , Cappello, S., Vannuccini, M.L., Corsi, I.. (2020) Nanoplastics affect moulting and faecal pellet sinking in Antarctic krill (Euphausia superba) juveniles. Environment International, 143. 11 pp. 10.1016/j.envint.2020.105999
• Smeaton C. Augmentation of global marine sedimentary carbon storage in the age of plastic. Limnology and Oceanography Letters. 2021 Jun;6(3):113-8.

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