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T. A. Aragaw and B. A. Mekonnen
2 Review Methods and Data Treatment
A comprehensive literature review of published articles was retrieved using the
ISI Web of Science, Scopus, PubMed database, and other research-researcher
networks (Google Scholar, Mendeley, and ResearchGate) for plastics and MPs study
published up to September 2020. The keyword queries included ‘Microplastics,
‘microplastics occurrence’ in a combination of ‘biota’, ‘ingestion/uptake/transfer’,
and ‘effects/impacts/toxicity’. The retrieved publications were then previewed separately to eliminate replicates, irrelevant, and unrelated literature. Furthermore, the
retrieved published materials, such as research articles, review articles, case studies,
technical reports, short communications, and books were downloaded. Further, the
downloaded documents were screened by type of the studied water body (freshwater
and marine water), biological groups of studied biota, the observed occurrence of
MPs in biota, the observed ecotoxicological effects of MPs, the detected ecotoxicological effects of combined MPs, and associated pollutants with respective of
countries. Then, published materials are categorized based on research scopes such
as the occurrence of MPs in biota studies, ecotoxicity observed in the global aquatic
system including across countries such as rivers, lakes, oceans, and gulfs and bay
were selected. The impact of MPs associated with other contaminants for the range
of fauna and flora from global water systems was also included.
3 The Occurrence of Microplastics in Aquatic Biota
MPs (<5 mm) have been discovered all over the world in a diversity of aquatic
biota, comprising bivalves, birds, and fish. Several laboratory investigations have also
revealed the existence of MPs in biota through direct ingestion or trophic transfer from
contaminated prey to a range of trophic levels. Hence, MPs have been increasingly
perceived and quantified in marine and freshwater environments and become highly
bioavailable to marine and freshwater organisms [16, 19, 20].
For instance, a recent study by Sathish et al. (2020) assessed the incidence of
MPs ingestion in seawater fish species samples from different habitats of Thirespuram coastal water in Tuticorin, southeast coast of India (Table 1). According to
the authors [21], MPs <500 μm were identified in the fish gastrointestinal tracts
with a concentration range of 0.11 ± 0.06–3.64 ± 1.7 items/individual fish which
is equivalent to 0.0002 ± 0.0001–0.2 ± 0.03 items/g gut weight in the samples.
In addition, FTIR-ATR analysis shown the different shapes of MPs including fiber,
fragment, film, and foam in the samples of water and fish species. As confirmed
by FTIR-ATR, small-sized (<500 μm), fibers, and blue colored PE were the dominantly found plastics in water and fish. Regardless of the plastic polymer identity
found in the fishes, PE was the most frequently recorded MP, followed by PS and
polyamide. Furthermore, the abundance of MPs in fishes is a function of the concentration levels of MPs in the Thirespuram coastal water environment. For example, the
T. A. Aragaw and B. A. Mekonnen
2 Review Methods and Data Treatment
A comprehensive literature review of published articles was retrieved using the
ISI Web of Science, Scopus, PubMed database, and other research-researcher
networks (Google Scholar, Mendeley, and ResearchGate) for plastics and MPs study
published up to September 2020. The keyword queries included ‘Microplastics,
‘microplastics occurrence’ in a combination of ‘biota’, ‘ingestion/uptake/transfer’,
and ‘effects/impacts/toxicity’. The retrieved publications were then previewed separately to eliminate replicates, irrelevant, and unrelated literature. Furthermore, the
retrieved published materials, such as research articles, review articles, case studies,
technical reports, short communications, and books were downloaded. Further, the
downloaded documents were screened by type of the studied water body (freshwater
and marine water), biological groups of studied biota, the observed occurrence of
MPs in biota, the observed ecotoxicological effects of MPs, the detected ecotoxicological effects of combined MPs, and associated pollutants with respective of
countries. Then, published materials are categorized based on research scopes such
as the occurrence of MPs in biota studies, ecotoxicity observed in the global aquatic
system including across countries such as rivers, lakes, oceans, and gulfs and bay
were selected. The impact of MPs associated with other contaminants for the range
of fauna and flora from global water systems was also included.
3 The Occurrence of Microplastics in Aquatic Biota
MPs (<5 mm) have been discovered all over the world in a diversity of aquatic
biota, comprising bivalves, birds, and fish. Several laboratory investigations have also
revealed the existence of MPs in biota through direct ingestion or trophic transfer from
contaminated prey to a range of trophic levels. Hence, MPs have been increasingly
perceived and quantified in marine and freshwater environments and become highly
bioavailable to marine and freshwater organisms [16, 19, 20].
For instance, a recent study by Sathish et al. (2020) assessed the incidence of
MPs ingestion in seawater fish species samples from different habitats of Thirespuram coastal water in Tuticorin, southeast coast of India (Table 1). According to
the authors [21], MPs <500 μm were identified in the fish gastrointestinal tracts
with a concentration range of 0.11 ± 0.06–3.64 ± 1.7 items/individual fish which
is equivalent to 0.0002 ± 0.0001–0.2 ± 0.03 items/g gut weight in the samples.
In addition, FTIR-ATR analysis shown the different shapes of MPs including fiber,
fragment, film, and foam in the samples of water and fish species. As confirmed
by FTIR-ATR, small-sized (<500 μm), fibers, and blue colored PE were the dominantly found plastics in water and fish. Regardless of the plastic polymer identity
found in the fishes, PE was the most frequently recorded MP, followed by PS and
polyamide. Furthermore, the abundance of MPs in fishes is a function of the concentration levels of MPs in the Thirespuram coastal water environment. For example, the