4 Impact and Fate of Microplastics in the Riverine …
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4.4 Aquatic Ecotoxicity of Microplastics
4.4.1 Toxic Effect of MPs Uptake
After entering to the aquatic system, the mobility and disintegration process generates a blend of parent plastic particles, fragmented particles and other non-polymeric
degradation products. Thus, the exposure effect of this complex blend of plastics and associated chemicals to aquatic organisms varies within the time-space.
The uptake of MPs by aquatic organisms occurs directly from water column and
sediment, and the most important uptake routes include ingestion, dermal uptake
or through respiratory surfaces. It was reported that the toxicity of MPs could
affect all aquatic organisms through its trophic transfer potential (Farrell and Nelson
2013). It was reported that the freshwater zooplankton Bosminacoregoni uptakes PS
beads (2–6 µm) when exposed and could not differentiate between MPs and algae
(Bern 1990). However, the study also reports that Daphnia cucullata can differentiate between PS MPs and preferentially uptook algal cell. In contrast, another study
reports that D. magna could readily ingest nanobeads and microbeads of PS and
retained to greater extent within the organism (Rosenkranz et al. 2009). The chronic
effect of secondary MPs (mean size 2.6 µm) against D. magna was also studied
and found that it leads to elevated mortality, increased inter-brood period, reproduction disability at concentration of 105,000 MPs particles L
−1 (Ogonowski et al.
2016). The trophic transfer of MPs was observed from blue mussels (Mytilus edulis)
to crabs (Carcinusmaenas) (Farrell and Nelson 2013). The mussels exposed to PS
MPs (0.5 µm) at concentration of 1 million particles mL
−1 was able to transfer PS
microsphere to crab haemolymph (15,033 particles mL
−1 ) within 24 h.
The shape and size of MPs play important role in the uptake process to the biota.
A smaller particle size of MPs, mimicking food particles, will be better ingested by
the organism than larger size. Angular-type MPs are more refrained to dislodge than
smooth spherical particles and thus can cause obstruction to gills and digestive tract.
Physical effect of microplastics ingestion on the aquatic organisms has been reviewed
recently, and the mechanisms include blockages of the digestive system, blockages
of feeding appendages, abrasion of tissues, reduction in enzyme production, lower
feeding stimulation, embedment in issues, decreased growths, nutrient dilution, lower
steroid hormone levels and impaired reproduction (Wright et al. 2013a, b). Biological
effect of nano and microplastics against some aquatic organisms is listed in Table 4.1.
4.4.2 Toxic Effect of Leaching Chemicals
Since commercial plastics are made of petroleum resources and consist specifically
of synthetic polymers viz. PE, PP, PS, polyvinyl chloride (PVC), etc., they differ
in chemical and physical properties such as density, porosity, thermal conductivity
103
4.4 Aquatic Ecotoxicity of Microplastics
4.4.1 Toxic Effect of MPs Uptake
After entering to the aquatic system, the mobility and disintegration process generates a blend of parent plastic particles, fragmented particles and other non-polymeric
degradation products. Thus, the exposure effect of this complex blend of plastics and associated chemicals to aquatic organisms varies within the time-space.
The uptake of MPs by aquatic organisms occurs directly from water column and
sediment, and the most important uptake routes include ingestion, dermal uptake
or through respiratory surfaces. It was reported that the toxicity of MPs could
affect all aquatic organisms through its trophic transfer potential (Farrell and Nelson
2013). It was reported that the freshwater zooplankton Bosminacoregoni uptakes PS
beads (2–6 µm) when exposed and could not differentiate between MPs and algae
(Bern 1990). However, the study also reports that Daphnia cucullata can differentiate between PS MPs and preferentially uptook algal cell. In contrast, another study
reports that D. magna could readily ingest nanobeads and microbeads of PS and
retained to greater extent within the organism (Rosenkranz et al. 2009). The chronic
effect of secondary MPs (mean size 2.6 µm) against D. magna was also studied
and found that it leads to elevated mortality, increased inter-brood period, reproduction disability at concentration of 105,000 MPs particles L
−1 (Ogonowski et al.
2016). The trophic transfer of MPs was observed from blue mussels (Mytilus edulis)
to crabs (Carcinusmaenas) (Farrell and Nelson 2013). The mussels exposed to PS
MPs (0.5 µm) at concentration of 1 million particles mL
−1 was able to transfer PS
microsphere to crab haemolymph (15,033 particles mL
−1 ) within 24 h.
The shape and size of MPs play important role in the uptake process to the biota.
A smaller particle size of MPs, mimicking food particles, will be better ingested by
the organism than larger size. Angular-type MPs are more refrained to dislodge than
smooth spherical particles and thus can cause obstruction to gills and digestive tract.
Physical effect of microplastics ingestion on the aquatic organisms has been reviewed
recently, and the mechanisms include blockages of the digestive system, blockages
of feeding appendages, abrasion of tissues, reduction in enzyme production, lower
feeding stimulation, embedment in issues, decreased growths, nutrient dilution, lower
steroid hormone levels and impaired reproduction (Wright et al. 2013a, b). Biological
effect of nano and microplastics against some aquatic organisms is listed in Table 4.1.
4.4.2 Toxic Effect of Leaching Chemicals
Since commercial plastics are made of petroleum resources and consist specifically
of synthetic polymers viz. PE, PP, PS, polyvinyl chloride (PVC), etc., they differ
in chemical and physical properties such as density, porosity, thermal conductivity