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Invading the remote?: microplastics in seawater and emperor penguins from the Weddell Sea and Dronning Maud Land, Antarctica

Leistenschneider, Clara. Invading the remote?: microplastics in seawater and emperor penguins from the Weddell Sea and Dronning Maud Land, Antarctica. 2024, Doctoral Thesis, University of Basel, Faculty of Science.

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Abstract

The escalating threat of plastic waste has raised environmental concerns in recent decades. Since their
introduction in the early 20th century, plastics have revolutionized many industries, evolving from a
niche product to a cornerstone of modern manufacturing and consumer products that are an integral part
of everyday life. The characteristics that make plastics so widely used, such as their durability and light
weight, also make them persistent in the environment. Their increasing prevalence in the environment,
particularly the marine environment, and the chemical additives associated with plastics have led to
growing concern in recent decades. Each year, an estimated 11 million tons of plastics enter the oceans,
where they are dispersed by ocean currents and broken down into smaller fragments under the influence
of environmental forces. These fragmented microplastics (MPs) have been detected in marine habitats
around the world, reaching even the most remote areas, including the polar regions.
Often regarded as the last pristine wilderness, Antarctica and the adjacent Southern Ocean are to a
certain extent isolated by the robust Antarctic Circumpolar Current, which limits the influx of water
masses and organisms from the northern oceans. Despite a relatively low human presence compared to
other global regions, increasing tourism and fishing pose emerging challenges to the unique and fragile
local biota, exacerbated by global warming and accelerated ice loss. Evidence of MP contamination in
the Southern Ocean and Antarctica has raised significant concerns as a potential additional stressor to
local ecosystems. Studies of MP contamination in the most accessible and anthropogenically impacted
regions of the Southern Ocean suggest that local human activities contribute to the MP load. Little is
known about the state of MP contamination in regions considered pristine with negligible human
activity. The Weddell Sea and the ocean off Dronning Maud Land (WS/DML) represent the highlatitude
Southern Ocean, characterized by circumpolar currents and deep water formation that contribute
to the global thermohaline circulation, and by a perennial sea ice cover, making the region difficult to
access.
This thesis addresses critical knowledge gaps about MPs in the Southern Ocean by investigating
seawater from the WS/DML for the occurrence and distribution of MPs, including MPs as small as
11 μm that have been overlooked in previous studies, and by evaluating an approach to analyze ship
paint fragments, a challenging MP type that has been commonly encountered in the Southern Ocean. In
addition, the extent to which MPs have already penetrated the local food web is evaluated by
investigating MP uptake in an endemic Antarctic apex predator.
By sampling surface and subsurface waters for MPs (>300 μm), we provided the first evidence of MP
contamination in the pristine WS/DML, with MP concentrations comparable to those reported for
regions significantly more impacted by human activity. The regular occurrence of fragments resembling
paint from the research vessel (RV) Polarstern, from which we have sampled, led us to address the
methodological challenges of analyzing and comparing these complex MP types. By combining two
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forensic methods, ATR-FTIR and micro-XRF, complemented by multivariate statistics, we were able
to trace 89% of these particles back to the RV Polarstern, further demonstrating that the ship emitted
paint fragments into the environment while operating.
With evidence of MP contamination in the seawater of this pristine region, we asked whether the local
biota was affected. Examination of the gizzard contents of emperor penguin chicks from the Atka Bay
colony revealed no evidence of MP (>500 μm) ingestion by chicks fed via regurgitation by their parents
foraging in the study region. This suggests that emperor penguins, and thus the underlying food web,
are still negligibly affected. The precise contamination control in this study further demonstrates the
need for meticulous protocols to avoid sample contamination and overestimation of MP counts.
While the body of scientific literature on MPs contamination in the Southern Ocean has expanded over
the course of this thesis, a critical gap in our knowledge remained: the occurrence of the smallest MPs
in the Southern Ocean, which have been shown to be particularly abundant in other marine regions of
the world, and additionally pose an increased threat to marine biota. We therefore shifted the focus of
our research to small MPs (11–50 μm), a critical size class for understanding the broader ecological
impacts of microplastic pollution. The participation on another expedition to the southern Weddell Sea
allowed us to sample surface water for MPs as small as 11 μm in size, which were subsequently analyzed
by micro-FTIR, revealing surprisingly high concentrations of MPs in this size class found in all samples.
This emphasizes the need for further research targeting these small MPs.
Finally, with three methodologically distinct but related studies, this thesis shows that the WS/DML is
no less affected by MP pollution than other regions in the Southern Ocean with much higher human
activity, suggesting long-range transport from these regions to the study area. While large MPs do not
appear to have a significant impact on the local food web, more research is needed on small MPs. The
high prevalence of small microplastics in the marine abiotic environment and the observed emission of
paint fragments call for mitigation measures to prevent potential impacts on the fragile local ecosystems.
The distribution pattern of MP concentrations and polymer diversity, similarly observed in both studies
on water samples from the WS/DML, further suggests that MPs are subject to complex environmental
dynamics and pathways in the study region, requiring more systematic sampling and multidisciplinary
studies in the future to provide a comprehensive understanding and support decision makers.
Advisors:Burkhardt-Holm, Patricia
Committee Members:Gerdts, Gunnar and Heiri, Oliver and Bluhm, Bodil
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Integrative Biologie > Aquatische Ökologie (Holm)
UniBasel Contributors:Heiri, Oliver
Item Type:Thesis
Thesis Subtype:Doctoral Thesis
Thesis no:15589
Thesis status:Complete
Number of Pages:1 Band (verschiedene Seitenzählungen)
Language:English
Identification Number:
  • urn: urn:nbn:ch:bel-bau-diss155894
edoc DOI:
Last Modified:23 Jan 2025 08:47
Deposited On:22 Jan 2025 16:25

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