The project Arctic Fibre, within the Fram Centre research programme Plastic in the Arctic, is a collaboration between SINTEF Ocean, Akvaplan-niva, and NILU, and investigates the effects UV degradation and biofilm formation have on the behaviour of microplastic fibres.
As part of this endeavour, Australian Alex Abrahams is doing a thesis project where she examines the interactions between microfibres and the green sea urchin.
Although named after the Norwegian town of Drøbak, the green sea urchin (Strongylocentrotus droebachiensis) is a common component of the benthos throughout northern seas, both on the Atlantic and the Pacific side. Alex investigates whether biofilm formation on microfibres has an effect on their ingestion or egestion by the sea urchins. In the summer of 2020, she collected sea urchins near the shore on Kvaløya, and conducted an experimental study, exposing the sea urchins to both microplastic fibres (blue acrylic) and a natural control fibre (wool) to see if the fibres were ingested, egested, and for how long they remain in the intestinal tract. Some fibres were incubated (“aged”) in natural seawater for two weeks to allow a biofilm to form on their surface.
Then, Alex ran experiments where five groups of sea urchins were exposed to clean or aged acrylic fibres, clean or aged wool, or a control condition without fibres.
The urchins were measured and put into individual beakers of seawater, along with fibres (except the controls) and a piece of seaweed as food source. After 48 hours, Alex dissected half of the urchins and placed the other half in clean (fibre-free) water for depuration.
Faecal pellets from these urchins were collected after 2, 3 and 5 days of incubation. Because of the nice weather and the Kvaløya summer heat, lab activities were moved to the jetty outside the Akvaplan-niva lab at Kraknes. Later, the ethanol-preserved faecal pellets were analysed under the microscope at the Fram Centre to count and measure the fibres the urchins had egested with their faeces.
Alex found the highest numbers of fibres in pellets from the wool exposures after two days of incubation. In the faecal pellets from urchins exposed to acrylic fibres, the number of fibres per pellet was higher for aged fibres than for clean ones.
After three and five days, no acrylic fibres were found in the faeces and only very few wool fibres were present. This seems to suggest that the acrylic fibres are egested quickly, within two days.
They may also be more durable, and the high number of wool fibres in the faecal material may point to degradation during the digestion process, such that wool fibres break into several pieces.
In a next step, Alex will analyse the urchin gut contents for fibres. If there is retention of fibres in the intestines, this may increase the possibility of ecotoxicological effects on the urchins and/or trophic transfer of fibres from the urchins to their predators, such as sea stars, crabs, large fish, mammals, birds – and humans.
The year 2020 has been full of surprises, characterised by continuous readjustment and change. The difficulties of the pandemic have been felt by everyone, not least by our students, who had cruises, fieldwork, conferences, and travel scheduled this year. We were lucky to be able to offer Alex field and lab facilities during this period and prevent delays in completing her degree. We look forward to more exciting results from the Arctic Fibre project in 2021.