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Browsing by Subject "pehmeä pohja"

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  • Mustonen, Anna-Riina (2020)
    In this Master’s thesis, I investigated the number of microplastics (< 5 mm) in three different groups of benthic invertebrates found in the Baltic Sea: the clam Limecola balthica, the polychaete Marenzelleria spp. and the bloodworm Chironomus spp. larvae. I also investigated the number of microplastics in the soft sediments that are the natural habitats of these animals. I collected the samples along the coast of the Gulf of Finland, between Hanko, Helsinki, and Kotka. To extract the microplastics from the samples I used density separation, hydrogen peroxide and enzymes. I analyzed the samples by focal plane array µFTIR and the spectra were automatically compared to a reference library by MPHunter software. According to this study, the benthic invertebrates are exposed to high quantities of microplastics in their natural habitat, and the animals end up ingesting microplastics. The number of microplastics in the sediment samples were high (between 0–10 145 kg-1 and 1 847–93 973 kg-1 DW sediment), and 90% of them were <300 µm sized particles that the animals used in this study normally ingest, and 54 % were <100 µm sized particles that the animals prefer the most. On average, all the animals had ingested the smaller microplastics that were available in sediments. Despite the high concentration of microplastics in the sediments, the animals had ingested only low numbers of microplastics per individual on average (L. balthica 0,11 ± 0,05 pcs., Marenzelleria spp. 0,46 ± 0,63 pcs., and Chironomus spp. 0,27 ± 0,19 pcs.). No relationship was found between the three different animal groups and the presence of ingested plastic particles, so the animal groups seem to be equally exposed to microplastics. No relationship was either found between the animal groups and the sizes of ingested microplastics. The plastic materials found in the animals and sediments (PA, PP, PE, PET, PMMA and PVC) are commonly used plastic materials. Most of these materials are used in disposable packaging and fishing gear that are the most common sources of microplastics found in marine environments. Although the number of ingested microplastics in benthic invertebrates in the Gulf of Finland seems to be low, the exposure to the microplastics can still be high during their lifetime. The results of this study depict the presence of microplastics in animals during a certain time. The low number of ingested microplastics may present the fact that microplastics do not accumulate in the animals, but rather pass through the digestive system in a short time (2–4 h). The ingested microplastics pose a risk to benthic invertebrates causing them physical and chemical harm. Oxidizing and bioturbating the sediments and as nutrition to other animals the benthic invertebrates have an important role in the Baltic Sea ecosystem, and therefore the consequences of the microplastic in benthic invertebrate community might be far-reaching. It is important to investigate the long term impact of microplastics on benthic invertebrates in order to estimate the real consequences to the marine ecosystems.