Effects of polystyrene microplastics on early stages of two marine invertebrates with different feeding strategies

Nowadays, microplastics represent one of the main threats to marine ecosystems, being able to affect organisms at different stages of their life cycle and at different levels of the food web. Although the presence of plastic debris has been reported in different habitats and the ability to ingest it has been confirmed for different taxa, few studies have been performed to elucidate the effects on survival and development of marine animals. Thus, we explored the effects of different environmental concentrations of polystyrene microbeads on the early stages of two invertebrate species widespread in the Mediterranean shallow waters: the pelagic planktotrophic pluteus larvae of the sea urchin Paracentrotus lividus and the filter-feeding sessile juveniles of the ascidian Ciona robusta. We evaluated the effects on larvae and juvenile development and determined the efficiency of bead ingestion. The feeding stages of both species proved to be extremely efficient in ingesting microplastics. In the presence of microbeads, the metamorphosis of ascidian juveniles was slowed down and development of plutei altered. These results prompted the necessity to monitor the populations of coastal invertebrates since microplastics affect sensitive stages of life cycle and may have consequences on generation recruitment.

S. Messinetti, S. Mercurio, M. Parolini and al., Environmental Pollution, Volume 237, June 2018, Pages 1080-1087

The article

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Microplastics Affect Energy Balance and Gametogenesis in the Pearl Oyster Pinctada margaritifera

Plastic pollution in the environment is increasing at global scale. Microplastics (MP) are derived from degradation of larger plastic items or directly produced in microparticles form (<5 mm). Plastics, widely used in structures and equipments of pearl farming, are a source of pollution to the detriment of the lagoon ecosystem. In order to evaluate the impact of MP on the physiology of Pinctada margaritifera, a species of ecological and commercial interests, adult oysters were exposed to polystyrene microbeads (micro-PS of 6 and 10 μm) for 2 months. Three concentrations were tested: 0.25, 2.5, 25 μg L-1 and a control. Ingestion and respiration rate and assimilation efficiency were monitored on a metabolic measurement system to determine the individual energy balance (Scope For Growth, SFG). Effects on reproduction were also assessed. The assimilation efficiency decreased significantly according to micro-PS concentration. The SFG was significantly impacted by a dose-dependent decrease from 0.25 μg L-1 (p < 0.0001). A negative SFG was measured in oysters exposed to 25 μg L-1. Gonads may have provided the missing energy to maintain animals’ metabolism through the production of metabolites derived from germ cells phagocytosis. This study shows that micro-PS significantly impact the assimilation efficiency and more broadly the energy balance of P. margaritifera, with negative repercussions on reproduction.

Tony Gardon, Céline Reisser, Claude Soyez, Virgile Quillien, and Gilles Le Moullac, Environ. Sci. Technol., Just Accepted Manuscript, April 5, 2018

Accumulation, tissue distribution, and biochemical effects of polystyrene microplastics in the freshwater fish red tilapia (Oreochromis niloticus)

While the presence of microplastics (MPs) in marine environments has been detected worldwide, the importance of MPs pollution in freshwater environments has also been emphasized in recent years. However, the body of knowledge regarding the biological effects of MPs on freshwater organisms is still much more limited than on marine organisms. The aim of the present study was to evaluate the accumulation and tissue distribution of MPs in the freshwater fish red tilapia (Oreochromis niloticus), as well as the biochemical effects of MPs on O. niloticus. During 14 days of exposure to 0.1 μm polystyrene-MPs at concentrations of 1, 10, and 100 μg L−1, the MPs concentrations in various tissues of O. niloticus generally increased over time following the order gut > gills > liver ≈ brain. Moreover, the acetylcholinesterase (AChE) activity in the fish brain was inhibited by MPs exposure, with a maximum inhibition rate of 37.7%, suggesting the potential neurotoxicity of MPs to freshwater fish. The activities of cytochrome P450 (CYP) enzymes [7-ethoxyresorufin O-deethylase (EROD) and 7-benzyloxy-4-trifluoromethyl-coumarin O-dibenzyloxylase (BFCOD)] in the fish liver exhibited clear temporal variabilities, with significant decreases followed by elevations compared to the control. The alterations of the EROD and BFCOD activities indicate the potential involvement of CYP enzymes for the metabolism of MPs. The activity of antioxidative enzyme superoxide dismutase (SOD) in the liver was significantly induced throughout the exposure period, while the malondialdehyde (MDA) content did not vary with MPs exposure, suggesting that the antioxidative enzymatic system in O. niloticus could prevent oxidative damage. These results highlight the ingestion and accumulation of MPs in different tissues of freshwater fish, which lead to perturbations in fish biological systems and should be considered in environmental risk assessment.

Jiannan Ding, Shanshan Zhang, Roger Mamitiana Razanajatovo and al., Environmental Pollution, Volume 238, July 2018, Pages 1-9

The article

Sorption of organic compounds by aged polystyrene microplastic particles

Microplastics that are released into the environment undergo aging and interact with other substances such as organic contaminants. Understanding the sorption interactions between aged microplastics and organic contaminants is therefore essential for evaluating the impact of microplastics on the environment. There is little information available on how the aging of microplastics affects their sorption behavior and other properties. We have therefore investigated the effects of an accelerated UV-aging procedure on polystyrene microplastics, which are used in products such as skin cleaners and foams. Physical and chemical particle characterizations showed that aging led to significant surface oxidation and minor localized microcrack formation. Sorption coefficients of organic compounds by polystyrene microplastics following aging were up to one order of magnitude lower than for pristine particles. Sorption isotherms were experimentally determined using a diverse set of probe sorbates covering a variety of substance classes allowing an in-depth evaluation of the poly-parameter linear free-energy relationship (ppLFER) modelling used to investigate the contribution of individual molecular interactions to overall sorption. The ppLFER modelling was validated using internal cross-validation, which confirmed its robustness. This approach therefore yields improved estimates of the interactions between aged polystyrene microplastics and organic contaminants.

Thorsten Hüffer, Anne-Katrin Weniger, Thilo Hofmann, Environmental Pollution, Volume 236, May 2018, Pages 218–225

The article

Comparisons of microplastic pollution between mudflats and sandy beaches in Hong Kong

Most of the previous studies of microplastic pollution on coastal habitats focused on high energy beaches although low energy areas such as mudflats are supposed to retain more microplastics, not to mention that mudflats are biologically more diverse. We quantified and characterized microplastics from 10 mudflats and 10 sandy beaches in Hong Kong spanning from the eastern to western waters. Sediment samples were collected at 1.0 m and 1.5 m above chart datum (CD) and at the strandline. Abundance of microplastics ranged between 0.58 and 2116 items kg−1 sediment with that on mudflats being ten times more than on beaches. Polyethylene (46.9%) was the most abundant and followed by polypropylene (13.8%) and polyethylene terephthalate (13.5%). Expanded polystyrene was the most abundant in the strandline samples but not at 1.0 m and 1.5 m above CD. Although previous studies have concluded that the input from Pearl River is a major source of microplastics on Hong Kong shores, this study has demonstrated that the contribution of local pollution sources such as discharge from sewage treatment plants to microplastic pollution should not be neglected.

Hoi-Shing Lo, Xiaoyu Xu, Chun-Yuen Wong, Siu-Gin Cheung, Environmental Pollution, Volume 236, May 2018, Pages 208–217

The article

Occurrence of microplastics in commercial fish from a natural estuarine environment

Microplastic ingestion has been reported for several marine species, but the level of contamination in transitional systems and associated biota is less known. The aim of this study was to assess the occurrence of microplastic ingestion in three commercial fish species: the sea bass (Dicentrarchus labrax), the seabream (Diplodus vulgaris) and the flounder (Platichthys flesus) from the Mondego estuary (Portugal). Microplastics were extracted from the gastrointestinal tract of 120 individuals by visual inspection and digestion solution. A total of 157 particles were extracted from 38% of total fish (96% fibers), with 1.67 ± 0.27 (SD) microplastics per fish. Significantly higher amount of ingested microplastics was recorded for D. vulgaris (73%). The dominant polymers identified by μ-FTIR were polyester, polypropylene and rayon (semi-synthetic fiber). It is reported for the first time the presence of this pollutant in fish populations from the Mondego estuary raising concerns on their potential negative effects.

Filipa Bessa, Pablo Barría, João M. Neto and al., Marine Pollution Bulletin, Volume 128, March 2018, Pages 575–584

The article

Polystyrene Nanoplastics-enhanced Contaminant Transport: Role of Irreversible Adsorption in Glassy Polymeric Domain

Nanoplastics (NPs) are becoming an emerging pollutant of global concern. A potential risk is that NPs may serve as carriers to increase the spreading of co-existing contaminants. In this study, we examined the effects of polystyrene nanoplastics (PSNPs, 100 nm), used as a model NP, on the transport of five organic contaminants of different polarity in saturated soil. The presence of low concentrations of PSNPs significantly enhanced the transport of nonpolar (pyrene) and weakly polar (2,2′,4,4′-tetrabromodiphenyl ether) compounds, but had essentially no effects on the transport of three polar compounds (bisphenol A, bisphenol F and 4-nonylphenol). The strikingly different effects of NPs on the transport of nonpolar/weakly polar versus polar contaminants could not be explained with different adsorption affinities, but was consistent with the polarity-dependent extents of desorption hysteresis. Notably, desorption hysteresis was only observed for nonpolar/weakly polar contaminants, likely because nonpolar compounds tended to adsorb in the inner matrices of glassy polymeric structure of polystyrene (resulting in physical entrapment of adsorbates), whereas polar compounds favored surface adsorption. This hypothesis was verified with supplemental adsorption and desorption experiments of pyrene and 4-nonylphenol using a dense, glassy polystyrene polymer and a flexible, rubbery polyethylene polymer. Overall, the findings of this study underscore the potentially significant environmental implication of NPs as contaminant carriers.

Jin Liu, Yini Ma, Dongqiang Zhu, Tianjiao Xia, Yu Qi, Yao Yao, Xiaoran Guo, Rong Ji, and Wei Chen, Environ. Sci. Technol., Just Accepted Manuscript, February 8, 2018