Examining microplastic ingestion in the eider duck

EXAMINING THE MICROPLASTIC INGESTION AND DRINKING BEHAVIOUR OF THE EIDER DUCK (SOMATERIA MOLLISSIMA)

By Lotta Ruha and Isabelle Valiulis. This project is supervised by Dr Stewart White, Senior Lecturer in Animal Biology, School of Life Sciences, University of Glasgow.

With the increasing quantities of plastic production, the levels of plastic debris in the oceans and terrestrial areas are rising in even the most remote areas, including Iceland. Interestingly, the South Icelandic coast has been found to contain very high levels of microplastics, even though this area has relatively low human activity. The microplastics could be brought to Iceland from continental Europe by the North Atlantic current (Lots et al., 2017). Europe contributes 18.5% of 340 million tonnes of plastic each year (Plastics Europe, 2018). However, ingestion of microplastics is the greatest threat for avian and marine species. Seabirds and waterfowl are used to study avian ingestion of plastics due to their predation and foraging habits in marine and terrestrial areas, and it has been estimated that by 2050, 99% of all seabirds will ingest microplastics (Wilcox et al., 2015).

Plastic debris has been found in marine water, sediment, invertebrates, and megafauna (Provencher et al., 2018). Microplastics are often defined within the parameter size between 5mm and .33mm, also defined through the need of microscopy to identify the pieces. Three common issues of ingestion are recognized as physical digestive blockage, chemical leaching, and accumulation of chemicals absorbed by the plastics (Arthur & Baker, 2008). Microplastics are strong absorbents for hydrophobic toxic pollutants that degrade slowly. They are ingested through the food chain and can cause neurotoxicity, oxidative damage, and energy-related changes due to bioaccumulation and biomagnification of these microplastics through the food chain (Wang et al., 2016). As a result, avian species located in East Iceland may be in threat of microplastic ingestion.

Eider ducks were chosen for this study to their faecal availability and population size. When the ducks are frightened, they will flush the nest and defecate on the eggs to ward off predators (McDougall & Milne, 1978). This allows for researchers to collect faecal samples from the incubating mothers. The eider ducks incubate for about 26 days. Incubating females do not eat during their incubation period and they lose about 40% of their body mass during incubation. They fast in order to spend less time away from their eggs and increase hatching success. However, they take short breaks from incubation during the incubation period to drink water, preen, and bathe (Criscuolo et al., 2000).

Little attention has been given to some avian species, specifically the eider duck (Somateria mollissima). Using this species of waterfowl, the study will observe the drinking water habits of in the remote Icelandic environment. These subjects will be observed by their faecal samples using methods similar to those described in previous studies done by University of Glasgow students in 2017 (Risk of Microplastic Ingestion in Coastal Birds of East Iceland) and in 2019 (An investigation into plastic pollution and its effect on breeding success in a colony of Arctic terns (Sterna paradisaea) in the Skálanes Nature and Heritage Centre, East Iceland). Over the 6 weeks, samples will be taken simultaneously around the reserve to determine the presence and bioaccumulation of plastics. We will be analysing plastic particles that are larger than 0.5mm, as particles that are smaller than this will be extremely difficult to define as plastics using the equipment available.

 

 Aims

  • To determine the fresh water sources used by the eider ducks for drinking.
  • To determine if the fresh drinking water available to the ducks may be a source of plastic pollution.
  • To identify whether the ducks are ingesting the plastic, and if so, what their level of ingestion is in comparison to the levels of plastic pollution in the water.

 

Hypotheses

  • The birds will prefer fresh water sources over salt water sources, even if the salt water source is closer to their nest. Birds will drink at their closest freshwater source in order to reduce their time away from the nest.
  • There will be a significant correlation between the presence of plastics in the birds’ faecal samples and in their drinking water. If little to no plastic is found in the drinking, little to no plastic should accumulate in the birds and plastics should not be observed in the faecal samples. If the plastic content in the water source is high, a significant percentage of it should accumulate in the birds and should be observed in the faecal samples.

 

Methods

Sample collection

  • The areas where the bird population drinks and breeds will be mapped using GPS.
  • The drinking behaviour of the birds will be observed using binoculars and documented with a camera. This is done in order to determine where their water source is from and how often the birds leave their nests for drinking and other reasons.
  • Water samples will be collected from the water sources which the eiders drink from. The samples will be brought to the research centre.
  • Faecal samples will be collected from the eider ducks in order to see whether they have ingested plastics. The faecal samples will be collected from eider nests after the nesting mother has left the nest. The sample will be collected quickly and quietly not to disturb other birds in the population. We will be following the guidelines set up by the BTO Nest Record Scheme Handbook to minimise any disturbance caused on the population. The faecal samples will be put in plastic bags or containers and brought back to the research centre. The samples are frozen for further analysis at a later time.

 

Analysing the samples

  • Faecal samples
    • Defreeze the faecal samples 30 minutes.
    • Add 10.0g of a faecal sample to a 50 ml beaker.
    • Prepare 25 ml of 0.3125% trypsin solution by adding 78.2μm of trypsin to another 50ml beaker and adding purified water until the 25ml mark. Add the solution to the beaker containing the faecal sample and add a magnet.
    • Place the beaker on a heated (45C) magnetic stirrer and stir for 30 minutes
    • Pour the solution into a 15ml centrifuge tube
    • Centrifuge 3500rpm at 15C for 15 minutes.
    • Pipette out the liquid part at the top of the solution and leave about 1ml of it over the solid settled part.
    • Homogenise the remaining solid and liquid parts.
    • Add three drops of the solution on a glass slide and cover with a cover slip.
    • View under a microscope at x10 magnification. Cover the entire sample including the borders. Count the amount of plastic fibres and their width and length.
    • Repeat for other faecal samples.
  • Water samples
    • Add 78.2μm of trypsin to a 50ml beaker. Add the water sample until the 25ml mark of the beaker and add a magnet.
    • Place beaker on a heated (45C) magnetic stirrer and stir for 30 minutes.
    • Pour the solution into a 15ml centrifuge tube
    • Centrifuge 3500rpm at 15C for 15 minutes.
    • Add three drops of a water sample to a glass slide and cover with a cover slip.
    • View under a microscope at x10 magnification. Cover the entire sample including the borders. Count the amount of plastic fibres and their width and length.
    • Repeat for other faecal samples.
  • After determining the amount of plastics in faecal and water samples, the amount of plastics per gram in the samples will be compared in order to see how much of the plastic has accumulated into the eiders from their drinking water.

 

References

Arthur, C. and Baker, J. (2008). Proceedings of the Internal Research Workshop on the Occurrence, Effects, and Fate of Microplastic marine debris. NOAA Technical Memorandum.

Lots, F., Behrens, P., Vijver, M., Horton, A. and Bosker, T. (2017). A large-scale investigation of microplastic contamination: Abundance and characteristics of microplastics in European beach sediment. Marine Pollution Bulletin, 123(1-2), pp.219-226.

Plasticseurope.org. (2018). Plastics- the facts 2018. [online] Available at: https://www.plasticseurope.org/application/files/6315/4510/9658/Plastics_the_facts_2018_AF_web.pdf [Accessed 26 Nov. 2019].

Provencher, J., Vermaire, J., Avery-Gomm, S., Braune, B. and Mallory, M. (2018). Garbage in guano? Microplastic debris found in faecal precursors of seabirds known to ingest plastics. Science of The Total Environment, 644, pp.1477-1484.

Wang, J., Tan, Z., Peng, J., Qiu, Q. and Li, M. (2016). The behaviors of microplastics in the marine environment. Marine Environmental Research, 113, pp.7-17.

Wilcox, C., Van Sebille, E. and Hardesty, B. (2015). Threat of plastic pollution to seabirds is global, pervasive, and increasing. Proceedings of the National Academy of Sciences, 112(38), pp.11899-11904.

Wright, C. (2017). Risk of microplastic ingestion by coastal birds in east Iceland. Undergraduate. University of Glasgow.

 

Follow

Follow this blog

Get every new post delivered right to your inbox.

Email address