Abstract
Marine microplastics pollution is a major environmental concern in marine ecosystems worldwide, yet the biological impacts of microplastics on the coastal biota are not yet fully understood. We investigated the impact of suspended microplastics on the energy budget of the mussels Mytilus coruscus using the Cellular Energy Allocation (CEA) approach. The mussels were exposed to control conditions (no microplastics) or to one of the three concentrations of 2 μm polystyrene microspheres (10, 104, and 106 particles/L) for 14 days, followed by 7 days of recovery. Exposure to high concentrations of microplastics (104 or 106 particles/L) increased cellular energy demand (measured as the activity of the mitochondrial electron transport system, ETS) and depleted cellular energy stores (carbohydrates, lipids, and proteins) in the mussels whereas exposure to 10 particles/L had no effect. Carbohydrate levels decreased already after 7 days of microplastics exposure and were restored after 7 days of recovery. In contrast, the tissue levels of lipids and proteins declined more slowly (after 14 days of exposure) and did not fully recover after 7 days following the removal of microplastics. Therefore, the total energy content and the CEA declined after 7–14 days of exposure to high microplastics concentrations, and remained suppressed during 7 days of subsequent recovery. These findings demonstrate a negative impact of microplastics on energy metabolism at the cellular level that cannot be restored during a short time recovery. Given a close link of CEA with the organismal energy balance, suppression of CEA by microplastics exposure suggests that bioenergetics disturbances might lead to decreases in growth and productivity of mussels’ populations in environments with heavy microplastics loads.
Highlights
An exponential increase in production and use of plastic materials leads to a rise in the amount of plastic waste in aquatic habitats worldwide (Andrady and Neal, 2009; Wang C. et al, 2020)
The energy stored in carbohydrates decreased in the digestive gland of the mussels exposed for 7–14 days to 104 or 106 particles/L compared with the control group (p < 0.05) (Figure 1A)
There was a tendency for concentration-dependent decrease in the carbohydrate content caused by microplastics, but the difference between the mussels exposed to the two highest tested microplastics concentrations was not statistically significant (p > 0.05)
Summary
An exponential increase in production and use of plastic materials leads to a rise in the amount of plastic waste in aquatic habitats worldwide (Andrady and Neal, 2009; Wang C. et al, 2020). Microplastics have been globally detected in aquatic environments, including beaches, sediments and water column (Zhao et al, 2018; Teng et al, 2019; Li et al, 2020; Wang C. et al, 2020) and are considered ubiquitous emergent contaminants in marine ecosystems (Rochman et al, 2019). One of the major concerns related to the environmental impacts of microplastics is their interference with organisms’ feeding (Botterell et al, 2019). Due to their small size, microplastics are ingestible by marine organisms and can accumulate in their digestive tract and other tissues potentially interfering with the digestion and nutrient uptake (Wright et al, 2013a,b). The ingestion of microplastics by marine biota has been extensively documented in the laboratory experiments and in the field (Khan and Prezant, 2018; Pinheiro et al, 2020; Xu et al, 2020; Müller, 2021), but its implications for nutrition and energy metabolism remain insufficiently well-studied in marine organisms, including suspension feeders (such as bivalves) that are considered one of the most susceptible trophic guilds for microplastics (Wright et al, 2013a,b)
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