Ecotoxicological Assessment of Microplastics in Freshwater Sources—A Review

Abstract

High living standards and a comfortable modern way of life are related to an increased usage of various plastic products, yielding eventually the generation of an increased amount of plastic debris in the environment. A special concern is on microplastics (MPs), recently classified as contaminants of emerging concern (CECs). This review focuses on MPs’ adverse effects on the environment based on their bioactivity. Hence, the main topic covered is MPs’ ecotoxicity on various aquatic (micro)organisms such as bacteria, algae, daphnids, and fish. The cumulative toxic effects caused by MPs and adsorbed organic/inorganic pollutants are presented and critically discussed. Since MPs’ bioactivity, including ecotoxicity, is strongly influenced by their properties (e.g., types, size, shapes), the most common classification of MPs types present in freshwater are provided, along with their main characteristics. The review includes also the sources of MPs discharge in the environment and the currently available characterization methods for monitoring MPs, including identification and quantification, to obtain a broader insight into the complex problem caused by the presence of MPs in the environment.

Effects of Polyester Fibers and Car Tire Particles on Freshwater Invertebrates

“…Furthermore, after 21 days of exposure, adults' ingestion was on average higher at the second highest concentration (0.015 g/L) compared with the highest concentration (0.15 g/L). The lower ingestion rate at the highest exposure concentration may have been caused by the increased agglomeration of tire particles in the test beakers, which has also been observed elsewhere (Miloloža et al, 2021). Daphnia magna commonly feeds on small, suspended particles in the water (planktonic algae), and their particle selectivity mainly depends on the particle size (Ebert, 2005;Gophen & Geller, 1984).…”

“…This ingestion has been shown to cause adverse effects such as intestinal damage, reduced growth, decreased reproduction, and decreased survival of aquatic organisms (Foley et al, 2018; Kögel et al, 2020). Most studies assessing the effects and ingestion of microplastics under laboratory conditions have been performed with polyethylene and polystyrene fragments or beads, which are not necessarily the most abundant microplastic types in the environment (De Ruijter et al, 2020; Kögel et al, 2020; Kutralam‐Muniasamy et al, 2020; Miloloža et al, 2021). Furthermore, data for freshwater benthic organisms remain very limited (Bellasi et al, 2020; Kögel et al, 2020), and most toxicity tests are performed without sediment, thus limiting the applicability of these data for conducting sediment risk assessments.…”

Assessment of the Influence of Size and Concentration on the Ecotoxicity of Microplastics to Microalgae Scenedesmus sp., Bacterium Pseudomonas putida and Yeast Saccharomyces cerevisiae

“…Therefore, scientists are still intensively conducting toxicity tests on various organisms. Test on the toxicity of MPs often use crustaceans Daphnia magna or zebrafish Danio rerio as test organisms [ 16 ]. Thus, ingested MPs have been reported to accumulate in body of Daphnia magna without significant effects on survival and reproduction for particle sizes 63–75 μm [ 17 ], while increased mortality and reduced reproductive capacity have been reported for sizes below 5 μm [ 18 , 19 ].…”

“…In addition, these tests are simple, inexpensive, and provide accurate results [ 21 ]. The most commonly used microorganisms are algae and their growth inhibition is monitored as a toxicity effect [ 16 ]. A decrease in chlorophyll content and photosynthetic activity due to lower expression of photosynthetic genes, shading effect, growth inhibition, oxidative stress, physical deterioration of microalgal cells, homoaggregation and heteroaggregation have been identified as the main negative effects for microalgae [ 22 ].…”

Converting mg/L to Particles/L: Reconciling the Occurrence and Toxicity Literature on Microplastics

“…Most adverse effects to date have been reported in the mg/L or μg/L range for micro- and nanoplastics, respectively. For example, half of the exposed Daphnia magna subjects were immobilized after 48h of exposure to 66.97 mg/L or 660 μg/L of 1 or 0.11 μm polystyrene (PS) beads, respectively (reviewed in ). The difference in units (particles/L in the occurrence literature vs .…”