78
T. A. Aragaw and B. A. Mekonnen
there was a great similarity in the abundance, size distribution, and color patterns of
MPs in clams those in sediment than in water [43].
Zhang et al. [44] examined MPs’ occurrence in biota, distribution, and physical
characteristics in the backwater area of Xiangxi River, China. Most importantly,
polyethylene and nylon (0.3–1.8 mm) MPs were detected in the digestion tracts of
26% of fish samples. In addition, MPs were detected in both surface water and sediment with concentrations ranging from 0.55 × 105 to 342 × 105 particles/km
2 and
80 to 864 particles/m
2 , respectively. Specifically, PE, PP, and PS polymers were identified in surface water, while PE, PP, PET, and pigments were observed in sediment
[44]. Additionally, Faura et al. [45] assessed plastic abundance, potential ingestion by
birds and fish, and the associated pollutants in Lakes Geneva, Switzerland. Evidence
shows the abundance of MPs (<5 mm) in 4.3 ± 2.6 particles per bird found in all
samples. The result suggests birds and fish are susceptible to MPs ingestion [45].
4 Interaction and Uptake Mechanism of Microplastics
by Aquatic Biota
MPs finally entered into water bodies by surface runoff, discharge from wastewater plants, and domestic/industrial drainage systems. MPs interaction with the
surrounding environment and aquatic biota is dynamic. After entering the aquatic
systems, MPs distributed into numerous environmental matrices such as surface
water, and benthic sediment causes bioavailability to the aquatic biota. Besides, MPs
are continually changing their fate and bioavailability in the aquatic system. The vast
majority of MPs in the oceans are supposed to originate from the weathering of larger
plastic debris [46], through mechanical and biological degradation. The weathering
of the large plastic debris is driven mainly by UV-radiation-induced photooxidation,
releasing low-molecular-weight polymer fragments resulting in fragmentation to a
range of smaller [47]. Then, these weathered MPs have contaminated the aquatic
biota inhabitants and interact with biota in different levels through ingestion and
tropical transfer as illustrated in Fig. 1 mainly through ingestion of plastic litter.
Ingestion is the most likely integration and uptake mechanism of MPs by marine
and freshwater biota [7]. Ingestion of plastics can be direct and indirect [19]. Laboratory tests have shown that amphipods and sea cucumber, barnacles mussels, and
lugworms can ingest MPs as the particles are in the size range of their prey [48].
Therefore, small plastic fragments have existed to invertebrates at the base of the food
shown in Fig. 1. Hence, direct ingestion is inherent in food consumption resulting
from unintentional intake through non-preset criteria of ingestion (by filter feeders),
or active selection to eat plastics instead of food. Small-size MPs give them the
possibility to be ingested by a wide range of biota in benthic and pelagic ecosystems.
Particles can also accumulate in sediment [16] suggesting that these would be available to many benthic communities. In some cases, the aquatic biota feeding method
does not permit a distinction between prey and anthropogenic items [49]. Secondly,
T. A. Aragaw and B. A. Mekonnen
there was a great similarity in the abundance, size distribution, and color patterns of
MPs in clams those in sediment than in water [43].
Zhang et al. [44] examined MPs’ occurrence in biota, distribution, and physical
characteristics in the backwater area of Xiangxi River, China. Most importantly,
polyethylene and nylon (0.3–1.8 mm) MPs were detected in the digestion tracts of
26% of fish samples. In addition, MPs were detected in both surface water and sediment with concentrations ranging from 0.55 × 105 to 342 × 105 particles/km
2 and
80 to 864 particles/m
2 , respectively. Specifically, PE, PP, and PS polymers were identified in surface water, while PE, PP, PET, and pigments were observed in sediment
[44]. Additionally, Faura et al. [45] assessed plastic abundance, potential ingestion by
birds and fish, and the associated pollutants in Lakes Geneva, Switzerland. Evidence
shows the abundance of MPs (<5 mm) in 4.3 ± 2.6 particles per bird found in all
samples. The result suggests birds and fish are susceptible to MPs ingestion [45].
4 Interaction and Uptake Mechanism of Microplastics
by Aquatic Biota
MPs finally entered into water bodies by surface runoff, discharge from wastewater plants, and domestic/industrial drainage systems. MPs interaction with the
surrounding environment and aquatic biota is dynamic. After entering the aquatic
systems, MPs distributed into numerous environmental matrices such as surface
water, and benthic sediment causes bioavailability to the aquatic biota. Besides, MPs
are continually changing their fate and bioavailability in the aquatic system. The vast
majority of MPs in the oceans are supposed to originate from the weathering of larger
plastic debris [46], through mechanical and biological degradation. The weathering
of the large plastic debris is driven mainly by UV-radiation-induced photooxidation,
releasing low-molecular-weight polymer fragments resulting in fragmentation to a
range of smaller [47]. Then, these weathered MPs have contaminated the aquatic
biota inhabitants and interact with biota in different levels through ingestion and
tropical transfer as illustrated in Fig. 1 mainly through ingestion of plastic litter.
Ingestion is the most likely integration and uptake mechanism of MPs by marine
and freshwater biota [7]. Ingestion of plastics can be direct and indirect [19]. Laboratory tests have shown that amphipods and sea cucumber, barnacles mussels, and
lugworms can ingest MPs as the particles are in the size range of their prey [48].
Therefore, small plastic fragments have existed to invertebrates at the base of the food
shown in Fig. 1. Hence, direct ingestion is inherent in food consumption resulting
from unintentional intake through non-preset criteria of ingestion (by filter feeders),
or active selection to eat plastics instead of food. Small-size MPs give them the
possibility to be ingested by a wide range of biota in benthic and pelagic ecosystems.
Particles can also accumulate in sediment [16] suggesting that these would be available to many benthic communities. In some cases, the aquatic biota feeding method
does not permit a distinction between prey and anthropogenic items [49]. Secondly,