# Microplastic Pollution: Chemical Characterization and Impact on Wildlife
## 3 Microplastics and Wildlife
### Microplastics in Aquatic Animals
SOD activity in both gut and liver tissues decreased as exposure time increased, with the maximum inhibition reaching 75% (14 th day) for gut SOD and 30% (7 th day) for liver SOD. Microphasics in association with zoonotic parasites are a great threat to shellfish health, which in turn, have a risk to enter the human and wildlife food chain by the consumption of affected shellfish. The author [PERSON] et al. [78] investigated zoonotic protozoan parasites such as _Toxoplasma gondii_, _Cryptosporidium parvum_, and _Giardia enterica_ with polyethylene microbeads and polyester microfibers and found that microplastics can increase the bioavailability of parasite and cause severe impacts on shellfish in the marine environment. In this study, the author used 27 bottles (15 treatment bottles, 9 control bottles which are plastic-free, and 3 negative controls) using 30 mL of seawater in each and microbeads and microfibers were tested separately in those bottles. The treatment and control bottles include microfiber treatment bottles (microfibers + parasites), microbead treatment bottles (microbeads + parasites), and negative controls either microbeads or microfibers only). Microplastic treatment bottles (n = 15, 5 per time point) contained microplastics as well as a mixture of 1000 ocysts of _T. gondii_, _G. enterica_, and _C. parvum_. In this experiment, microbead experiment bottles and microfibers experiment bottles contained 0.053 g (940 particles) and 0.000156 g (481 particles), respectively, and they used a concentration of 31 microbeads/mL and 16 microfibers/ mL in the first experiment and a concentration of 31 microplastics/mL in the second experiment. All three protozoan parasites were found on the surfaces of microplastics, including microbeads and microfibers. In the case of microbeads, parasite counts on these plastics increased over time. In contrast, G. _ enterica_ and _T. gondii_ parasite counts in seawater decreased over a 7-day period, but not _C. parvum_. Counts of _G. enterica_ associated with microbeads increased significantly (_p_ < 0.05) over each testing day. On day 7, _T. gondii_ numbers on the microbeads were significantly greater than on day 1, whereas _T. gondii_ concentrations in the seawater were significantly lower than on day 1. Results suggest parasites coagulate with MPs in solution, but further work is needed to assess the impact on animal health. Microplastics are present in the tissues of various wild coastal animals and are of great concern for transmission from infected tissues to the food chain of tertiary animals or humans. The authors [PERSON] et al. [79] investigated samples of the stomach, intestinal wall, liver, and muscle of flounders, cod, seabirds, otters, and seals, and found the highest level of microplastic in the cod liver which may be transferred throughout the food web of wild animals and birds. Local fishermen donated fresh or frozen birds and mammals to the study. The animals were mostly caught as bycatch in fishing nets and crab traps. Three otters (_Lutra lutra_), two sawbill ducks (red breasted merganser; _Mergus serrator_), and one common guillemot (common murre; _Uria aalge_) were delivered to the Norwegian Veterinary Institute (NVI) in Bergen for investigation of both microplastic and health parameters. One harbor seal (_Phoca vitulina_) was autopsied in the open air. Three cod (_Gadus morthua_) and three flounders (_Limanda limanda_) were caught exclusively for the project by Norwegian Hunter and Anglers Association volunteers and delivered fresh to NVI. Three additional otters were sampled for health parameters but were not included in the chemical MP investigation. All animals were autopsied in accordance with NVI guidelines (http://kvalitet/eknet/docs/pub/dok01304.htm accessed on 15 December 2022). Most organs' tissue samples, including tissues with obvious lesions, were fixed in 10% neutral buffered formalin, embedded in paraffin, and regularly processed into slices of 3-4 mm thickness for histopathological analysis.