Ingestion of small-sized and irregularly shaped polyethylene microplastics affect Chironomus riparius life-history traits

Microplastics (MPs) are emerging contaminants of freshwater ecosystems. Once in aquatic systems, most of these plastic particles undergo processes of fragmentation, biofouling, and sedimentation, resulting in increased concentrations of smaller sized and irregularly-shaped particles in the sediment. High levels of MPs in freshwater sediments can denote a potential threat to benthic and sediment-dwelling organisms such as dipteran larvae. This study evaluates the ecotoxicological effect of three pools of irregularly-shaped polyethylene (PE) microplastics (pools containing 90% of the particles within 32–63 μm (size-class A), 63–250 μm (size-class B) and 125–500 μm (size-class C)), with concentrations ranging from 1.25 to 20 g Kg−1 sediment, on the dipteran Chironomus riparius life-history traits. After ten days of exposure, larvae ingested PE particles typically in the 32–63 μm range, even when 90% of the particles possessed higher size (i.e., in size-classes B and C) and the larvae mandible allowed the ingestion of such bigger-sized particles. Thus, the number of ingested particles was higher in size-class A, followed by B and C, and led to a significant reduction with similar magnitude on larval growth (Lowest Observed Effect Concentrations (LOEC) = 2.5 g Kg−1 sediment DW) and a significant delay on imagoes emergence (e.g., LOEC = 1.5 g Kg−1 sediment DW for females). The results from this study show that the ingestion and persistence of small-sized polyethylene microplastics caused significant impairments on life-history traits of C. riparius. Considering their role on freshwater food-webs and the potential persistence of small-sized PE particles in their larval gut, these results also point for the potential adverse effects of small-sized microplastics at the community and ecosystem level.This study was supported by FCT through national funds (PIDDAC), and the cofunding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020 within the research project ComPET (POCI-01-0145-FEDER-030361) and CESAM (UID/AMB/50017). Also, by FCT and FSE/POCH, via a Post-Doc grant to A.L. Patricio Silva (SFRH/BPD/114870/2016), a Ph.D. grant to Carlos Silva (SFRH/BD/128134/2016) and a research contract under the program “Investigador FCT2015” to João L.T. Pestana (IF/01420/2015).publishe

Microplastic contamination and ecological status of freshwater ecosystems: a case study in two northern Portuguese rivers

Background: Most European rivers have not yet achieved “good” ecological status. In addition, the presence and abundance of microplastics (MPs) in freshwater is a matter of great concern to the scientific community. Methodology: This study assesses the ecological status of four sampling sites of Selho (S1–S4) and Costa-Couros (C1–C4) rivers (Guimarães, Portugal), and the abundance of MPs in sediments and benthic macroinvertebrates (Oligochaeta) from those sites. Results: All sites of both rivers under higher pressure did not reach a “good” ecological status (S2–S3, C2–C4) based on the macroinvertebrate community. High levels of nutrients were observed at all sites in both rivers (except C2), especially phosphorus. In the Oligochaeta’s gut of Costa-Couros river, the high number of MPs seems to be associated with their weight (95.25 ± 25.61 to 1069.00 ± 385.30 MPs g/fresh weight), suggesting the existence of malnutrition and digestive disorders, whereas the highest number of MPs in gut (134.00 ± 30.36 to 558.6 ± 100.70 MPs g/fresh weight) were found for the heaviest organisms of Selho. Conclusions: Thus, sites with higher ecological status do not necessarily have lower abundance of MPs. In the sediments, urbanization seems to be the main driver for MP contamination. MP contamination is pervasive across the sediments and Oligochaeta’s gut in both rivers. Since MPs have the potential to cause harm to environmental and human health, it is essential to monitor not only the ecological status of freshwaters, but also emerging pollutants such as MPs.This study was financially supported by the Guimarães City Council, by the Ministry of the Environment and Climate Action (Portugal) through the project “Aqualastic: Educar, Reduzir e Valorizar”, by the Foundation for Science and Technology (FCT) and the POPH/FSE (Human Potential Operational Program/European Social Fund) through funds of CESAM (UIDP/50017/2020; UIDB/50017/2020; LA/P/0094/2020), and by the project comPET (POCI-01-0145-FEDER-030361)

Oxidative damage and decreased aerobic energy production due to ingestion of polyethylene microplastics by Chironomus riparius (Diptera) larvae

Riverine sediments are major sinks of microplastics from inland anthropogenic activities, imposing a threat to freshwater benthic invertebrates. This study investigated the ingestion of three size-classes (SC) of irregularly shaped polyethylene microplastics (PE-MPs; SC I: 32-63 μm; II: 63-250 μm; III: 125-500 μm) after 48 h by dipteran larvae (detritivore/collector) Chironomus riparius, and the consequent effects on neurotransmission, energy allocation and oxidative stress. The tested PE-MPs concentrations (1.25; 5; 20 g kg-1) were within the range of concentrations reported in riverbanks from highly urbanised areas (1 - 9 g kg-1), except for 20 g kg-1 representing the worst-case scenario. After exposure to SC I, larvae presented high amounts (up to ∼2400 particles/organism) of PE-MPs in their guts, with an average size-range of 30-60 μm. In the SC II and III, larvae presented PE-MPs of higher diameter (up to 125 μm) and a visible gut obstruction. The high number of particles in the larval gut (SC I) and/or difficulties for their egestion (SC I, II and III) induced oxidative damage and reduced aerobic energy production. In addition, larvae exposed to SC II and III revealed depletion in their total lipid reserves as a consequence of lacking nutrients, and the ones exposed to SC III presented a decrease in their detoxification capacity. These results highlight that freshwater detritivores with low selective feeding behaviour (e.g., chironomids) are more prone to ingest microplastics, with potentially adverse effects on cellular metabolism, redox status and antioxidant-detoxification defences. These harmful effects at lower levels of the biological organisation may ultimately affect organisms' physiology and fitness.publishe

Microplastics in freshwaters: are benthic invertebrates at risk?

Microplastics contamination is an increasing environmental problem in freshwater ecosystems, with environmentally consequences as severe as in marine environments. However, studies on the ecological impact of such particles in these ecosystems remain scarce. Here, we show that sediments contaminated with polyethylene microbeads (sized 48 µm) led to a decrease in the growth and development of the dipteran C riparius which led to a delay in emergence of adult insects Furthermore, a 48 h exposure triggered an activation of immune system, induced oxidative damage, and altered energy metabolism. These findings highlight the potential deleterious effects of small sized microplastics 50 µm), at environmental relevant concentrations 1 2 g MPs/Kg sediment w/w), to C riparius and eventually to other benthic macroinvertebrate species.Thanks are due for Carlos Silva doctoral grant (SFRH/BD/128134/2016) and for the financial support to CESAM (UID/AMB/50017-POCI-01-0145-FEDER-007638), to FCT/MEC through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020.Not Publishe

Oxidative stress biomarkers in Senegal sole, Solea senegalensis, to assess the impact of heavy metal pollution in a Huelva estuary (SW Spain): Seasonal and spatial variation

The responseofwildfishtoheavymetalswasstudiedinsole(Solea senegalensis) collectedin2004, 2005 and 2006 at three sampling sites from Huelva estuary (SWSpain), in the vicinity of a petrochemical and mining industry. Heavy metals As, Cd, Cu, Fe, Pb and Zn were analyzed in samples collected from sediment, water and tissue (liver) to examine their bioconcentration and effects in fish such as lipid peroxidation (LPO), catalase (CAT;EC1.11.1.6), glutathione peroxidase (GPx; EC1.8.1.7), glutathione S-transferase (GST;EC2.5.1.18) and glutathione reductase (GR;EC1.11.1.6) were also analyzed in the fish liver.The results showed different effects in sole from diverse locations with varying degrees of pollution. Significant differences in LPO, CAT and GR activities between control fish and fish from sampling sites were observed as well as seasonal differences for biomarkers. Significant correlations were established between some biomarkers and heavy metals concentrations in liver, sediment and water. This study indicates the usefulness of integrating a set of biomarkers to assess the effects of pollutants in aquatic environments under complex mix of pollutants and chronic pollution situation

EROD activity and cytochrome P4501A induction in liver and gills of Senegal sole Solea senegalensis from a polluted Huelva Estuary (SW Spain).

EROD activity and induction cytochrome P4501A in liver and gills of Senegal sole, Solea senegalensis, from a heavy metal and PAH polluted estuary, was studied. Liver and gill CYP1A catalytic activity was assessed at the enzyme activity level-measured as 7-ethoxyresorufin-O-deethylase and cellular localization of CYP1A in the liver was studied using immunohistochemistry. Liver EROD was correlated with phenanthrene-type metabolites in liver and copper concentrations in water. Strong CYP1A occurrence was observed in acinar pancreatic cells, pancreatic duct epithelium and vascular system endothelium and negative/rare induction were observed in hepatocytes and sinusoidal endothelium. In gills, EROD activity showed a significant correlation with different fractions of heavy metals in sediment but no correlation was observed between EROD activity and PAHs. Strongly positive CYP1A associated staining of the vascular system endothelia and primary filament cells and a moderate staining of pillar cells in gills were observed. The results substantiated the utility of EROD activity and CYP1A induction measurement as biomarkers for use by aquatic toxicologists and indicate that catalytic assays and immunohistochemical assays appear to be sensitive to different kinds of pollutants being the use of both methods recommended for monitoring programs

Biomarkers responses in muscle of Senegal sole (Solea senegalensis) from a heavy metals and PAHs polluted estuary.

The biochemical responses in muscle, such as the enzymatic activities of acetylcholinesterase, lactate dehydrogenase and isocitrate dehydrogenase, were studied in sole (Solea senegalensis) collected in Huelva estuary (SW Spain), in the vicinity of a petrochemical and mining industry. The sampling sites showed different type and degree of pollution. The results demonstrated significant differences in muscle activities of AChE and IDH in Odiel and Tinto Rivers compared to control fish. LDH activity did not show any difference between sampling sites. Significant correlations were established between some biomarkers and heavy metals: AChE was correlated with Pb, Cd and Cu concentrations in water; IDH activity was correlated with Cd and Cu concentrations in water and As, Pb and Cd concentrations in sediments; LDH activity was correlated with As and Zn concentration in water and Cd concentration in sediment. Only one correlation was established between the biomarkers analysed and the concentrations of PAHs: benzo(b)fluoranthene concentration in sediment and IDH

Biochemical effects and polycyclic aromatic hydrocarbons (PAHs) in Senegal sole (Solea senegalensis) from a Huelva estuary (SW Spain).

Relations between several stress oxidative biomarkers and aromatic polycyclic hydrocarbon (PAH) concentrations have been studied in wild sole, Solea senegalensis collected in the vicinity of a petrochemical industry. Antioxidant enzyme activities in eco-toxicological studies constitute excellent markers for exposure to a large variety of pollutants. The 16 PAHs in sediment as well as oxidative damage (LPO), activity of catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR) and PAHs type metabolites in sole liver were analysed. Significant correlations (p<0.05) were established between some biomarkers as GST, GPx and CAT and PAHs metabolites in liver (naphthalene, pyrene and phenanthrene) and PAHs concentrations in sediments (fluoranthene, acenaphthene, anthracene and chrysene). PAHs accumulated in the sediment and organisms are inducers of antioxidant defences. GST, GPx and CAT were robust biomarkers showing correlations with both PAHs in sediments and liver PAH metabolites showing different responses to low and high molecular weight PAHs

The use of muscle biomarkers for assessing physiological effects of heavy metal pollution in the greater white-toothed shrew (Crocidura russula)

The greater white-toothed shrew Crocidura russula has been used as a sentinel species for estimating environmental risks to human populations. Previous studies in mining areas have focused on the liver of shrews as the primary target of physiological and metabolic changes due to heavy metal pollution. However, populations persist even when detoxification by the liver seems to be compromised and damage is observed. These pollutant-adapted individuals inhabiting contaminated sites may exhibit altered biochemical parameters that confer increased tolerance in various tissues other than the liver. The skeletal muscle tissue of C. russula might be an alternative tissue that allows the survival of organisms inhabiting historically polluted sites due to the detoxification of redistributed metals. Organisms from two heavy metal mine populations and one population derived from an unpolluted site were used to determine the detoxification activities, antioxidant capacity, and oxidative damage, as well as cellular energy allocation parameters and acetylcholinesterase activity (a biomarker of neurotoxicity). Muscle biomarkers differ between shrews from polluted sites and shrews from the unpolluted location, with the mine animals showing: (1) a decreased energy consumption concomitant with increased energy reserves and total available energy; (2) reduced cholinergic activity, suggesting an impairment of neurotransmission at the neuromuscular junction; (3) an overall decrease in detoxification capacity and enzymatic antioxidant response and a higher level of lipid damage. Also, some of these markers differed between females and males. These changes may have resulted from a decreased detoxifying capacity of the liver and could potentially bring about significant ecological effects for this highly active species. Heavy metal pollution induced physiological changes in Crocidura russula showing that skeletal muscle may serve as a backup sink organ allowing rapid species adaptation and evolution.publishe