Single contaminant and combined exposures of polyethylene microplastics and fluoranthene: accumulation and oxidative stress response in the blue mussel,Mytilus edulis

Abstract

The microplastic "vector effect" has received increasing attention. The aim of this study was to investigate the influence of polyethylene microplastic beads (PE MP) on accumulation and associated oxidative stress responses attributed to fluoranthene (Flu) in blue mussels, Mytilus edulis. Blue mussels were exposed for 96 h to four treatment groups: Flu-only, MP-only, Flu and MP coexposure, and Flu-incubated MP. Treatments were conducted at a low and high concentration (50 μg/L and 100 Flu μg/L and 100, and 1000 MP/mL). Results demonstrated that in both the gill and digestive gland, coexposure did not markedly affect Flu uptake, but this treatment significantly decreased tissue Flu concentrations. Antioxidant responses including activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), and levels of total glutathione (GSH) in both gills and digestive glands were significantly altered suggesting a perturbation of redox state induced by the exposure conditions. Although individual biomarkers varied, the biomarker profile enabled certain generalizations to be made. Antioxidant responses occurred more likely in gill tissue than in digestive gland. Individual contaminant exposures to Flu or MP led to varying responses, but coexposures and incubated exposures did not result in additive or synergistic effects. Exposure concentrations (i.e., low or high treatments) were not a consistent a predictor of response; and the internal Flu dose did not consistently predict outcome of various biomarkers. Importantly, MP-only exposure appeared to be capable of eliciting direct effects on the oxidative stress system as demonstrated by the activities of CAT and GPx. These findings warrant further investigation.

Microplastics, microfibres and nanoplastics cause variable sub-lethal responses in mussels (Mytilus spp.)

“…following a 7-day exposure to PS-MP, and Magara et al (2018) showed no effect on SOD activity in the gills or digestive glands of M. edulis exposed to 100-1000 PE-MP mL -1 for 4 days. Wang et al (2020) identified a non-significant increase in SOD activity in the digestive glands of the mussel Mytilus coruscus following 24 h exposure to microplastics, and no changes in SOD activity with longer exposure periods.…”

“…We posit that higher plastic concentrations may be sufficient to cause attrition within the gastro-intestinal tract resulting in the abrasion of tissues, leading to cellular damage and lipid peroxidation. It is recognised that oxidative stress responses can be variable, differing with genotype, age, reproductive status, feeding and temperature, and that a broader suite of biomarkers and wider literature should be considered in inferring biological pathways (Magara et al, 2018;Trestrail et al, 2020). Histological studies have shown that microplastics can permeate into the epithelial cells of the digestive gland resulting in epithelial thickening, the formation of granulocytomas and reduced epithelial cilia densities (Bråte et al, 2018;Paul-Pont et al, 2016;von Moos et al, 2012).…”

Bioaccumulation and biomagnification of microplastics in marine organisms: A review and meta-analysis of current data

“…Further, bioaccumulation of chemical additives associated with MP uptake has also been documented, albeit in fewer species [54,57,71]. Interestingly, in all six species examined, uptake of chemical additives was higher when exposed to the chemical alone compared to exposure alongside or on MPs [57,59,60,67,71]. For most of the studies reporting bioaccumulation of MPs or chemical additives, the concentrations in the surrounding environment were not measured, hindering the elucidation of potential exposure pathways.…”

“…A total of 4 species have been examined for contamination with chemical additive associated with MPs uptake under controlled laboratory exposures, namely the mussels Mytilus edulis [59] and Mytilus spp. [60], the clam Scrobicularia plana [61] and the amphipod Allorchestes compressa [57] (S7 Table in S1 File).…”

Health impacts of environmental contamination of micro- and nanoplastics: a review

“…Bivalves are a group of animals that lack some of the common molluscan organs, such as the radula and odontophore, so they cannot chew when they eat. All their ingested food goes directly into the digestive system and can be used in MNPs research [80][81][82][83][84][85]. Most bivalves are filter feeders, including oysters, clams, shellfish, mussels, etc.…”