Microplastics (MPs) are the most numerous debris reported in marine environments and assessment of the amounts of MPs that accumulate in wild organisms is necessary for risk assessment. Our objective was to assess MP contamination in mussels collected around the coast of Scotland (UK) to identify characteristics of MPs and to evaluate risk of human exposure to MPs via ingestion of mussels. We deployed caged mussels (Mytilus edulis) in an urbanised estuary (Edinburgh, UK) to assess seasonal changes in plastic pollution, and collected mussels (Mytilus spp and subtidal Modiolus modiolus) from eight sampling stations around Scotland to enumerate MP types at different locations. We determined the potential exposure of humans to household dust fibres during a meal to compare with amounts of MPs present in edible mussels. The mean number of MPs in M. modiolus was 0.086 ± 0.031 (SE, n = 6)/g ww (3.5 ± 1.29 (SE) per mussel). In Mytilus spp, the mean number of MPs/g ww was 3.0 ± 0.9 (SE, n = 36) (3.2 ± 0.52 (SE) per mussel), but weight dependent. The visual accuracy of plastic fibres identification was estimated to be between 48 and 50%, using Nile Red staining and FT-IR methodologies, respectively, halving the observed amounts of MPs in wild mussels. We observed an allometric relationship between the number of MPs and the mussels wet weight. Our predictions of MPs ingestion by humans via consumption of mussels is 123 MP particles/y/capita in the UK and can go up to 4620 particles/y/capita in countries with a higher shellfish consumption. By comparison, the risk of plastic ingestion via mussel consumption is minimal when compared to fibre exposure during a meal via dust fallout in a household (13,731–68,415 particles/Y/capita).

The effects of the biocide Triclosan, used in personal care products and known as a common environmental contaminant, on byssal apparatus were studied in the marine mussel Mytilus galloprovincialis. Experimental evidences indicated that an exposure for 7 days at a concentration of 10 μg/L induced marked alterations in the byssus gland resulting in a significant delay in byssus regrowth and in a decrease in threads resistance to traction. Such alterations in animals exposed to tidal and waves action would cause a significant loss in ecological fitness and severely impact on mussel survival. Triclosan release in coastal environments therefore should be more carefully monitored to prevent drastic consequences.

Warming and acidification are expected impacts of climate change to the marine environment. Besides, organisms that live in coastal areas, such as bivalves, can also be exposed to anthropogenic pollutants like pharmaceuticals (PhACs) and endocrine disrupting compounds (EDCs). In this study, the effects of warming and acidification on the bioconcentration, metabolization and depuration of five PhACs (sotalol, sulfamethoxazole, venlafaxine, carbamazepine and citalopram) and two EDCs (methylparaben and triclosan) were investigated in the mussel species (Mytilus galloprovincialis), under controlled conditions. Mussels were exposed to warming and acidification, as well as to the mixture of contaminants up to 15.7 μg L−1 during 20 days; followed by 20 days of depuration. All contaminants bioconcentrated in mussels with levels ranging from 1.8 μg kg−1 dry weight (dw) for methylparaben to 12889.4 μg kg−1 dw for citalopram. Warming increased the bioconcentration factor (BCF) of sulfamethoxazole and sotalol, whereas acidification increased the BCF of sulfamethoxazole, sotalol and methylparaben. In contrast, acidification decreased triclosan levels, while both stressors decreased venlafaxine and citalopram BCFs. Warming and acidification facilitated the elimination of some of the tested compounds (i.e. sotalol from 50% in control to 60% and 68% of elimination in acidification and warming respectively). However, acidification decreased mussels' capacity to metabolize contaminants (i.e. venlafaxine). This work provides a first insight in the understanding of aquatic organisms' response to emerging contaminants pollution under warming and acidification scenarios.

Heavy metal contamination has been widely studied in coastal areas around the world. However, integrative studies of heavy metals pollution by monitoring and characterizing sediments, organisms, and biomarkers as well as their holistic interactions are rare. Here, we selected a developed coastal area in eastern Guangdong, China as the study field. Heavy metal analysis (both in sediment and mussel) and biomarker tests, including neutral red retention time test (NRRT) and micronuclei (MN) test, were employed in the current research. Anthropogenic activities influenced the heavy metal levels in sediments. Significant relationships (p < 0.05) were observed in the concentrations of Cd, Cu, and Zn between sediments and transplanted mussel, and significant relationships (p < 0.05) were also observed in between the concentrations of Cd, Cu, and Zn in sediments and the NRRT of mussel. The potential ecological risk index (RI) of sediments significantly correlated with NRRT (R = −0.991, p < 0.05). In Hao River, where the highest RI of sediments was found, the highest MN frequency and the lowest NRRT in mussels were detected simultaneously. The results indicated that the heavy metal pollution might cause subcellular toxic and genotoxic effects on mussels, especially for those from polluted areas (i.e., Hao River). The present study suggests that the transplanted green-lipped mussels are suitable for assessing heavy metal pollution, especially for Cd, Cu, and Zn.

Glyphosate (GLY) is one of the most used herbicide worldwide. Considering that information concerning the impact of GLY on bivalves is scarce, in this study we evaluated for the first time the effects of environmentally realistic concentrations of GLY (10, 100 and 1000 μg/L) to the mussel Mytilus galloprovincialis. Mussels were exposed for 7, 14 and 21 days and several biomarkers were measured in haemocytes/haemolymph (total haemocyte counts, haemocyte diameter and volume, haemolymph pH, haemolymph lactate dehydrogenase activity, haemocyte lysate lysozyme and acid phosphatase activities), as well as in gills and digestive gland (antioxidant enzyme and acetylcholinesterase activities). The concentrations of GLY and its main metabolite aminomethylphosphonic acid in the experimental tanks were also measured. The MANOVA analysis demonstrated that the experimental variables considered (exposure concentration, exposure duration, and their interaction) affected significantly biomarker responses. In addition, the two-way ANOVA analysis indicated that GLY was able to affect most of the cellular parameters measured, whereas antioxidant enzyme activities resulted to be influenced moderately. Interestingly, exposure to GLY reduced significantly acetylcholinesterase activity in gills. Although preliminary, the results of this study demonstrated that GLY can affect both cellular and biochemical parameters in mussels, highlighting a potential risk for aquatic invertebrates.

The temporal and spatial trends in sediment of 22 poly- and perfluorinated (PFAS) compounds were investigated in the southern Great Lakes Erie and Ontario as well as Lake St. Clair. Surface concentrations measured by Ponar grab samples indicated a trend for greater concentrations near to urban sites. Mean concentrations ∑22PFAS were 15.6, 18.2 and 19 ng g−1 dm for Lakes St. Clair, Erie and Ontario, respectively. Perfluoro-n-butanoic acid (PFBA) and Perfluoro-n-hexanoic acid (PFHxA) were frequently determined in surface sediment and upper core samples indicating a shift in use patterns. Where PFBA was identified it was at relatively great concentrations typically >10 ng g−1 dm. However as PFBA and PFHxA are less likely to bind to sediment they may be indicative of pore water concentrations Sedimentation rates between Lake Erie and Lake Ontario differ greatly with greater rates observed in Lake Erie. In Lake Ontario, in general concentrations of PFAS observed in core samples closely follow the increase in use along with an observable change due to regulation implementation in the 1970s for water protection. However some of the more water soluble PFAS were observed in deeper core layers than the time of production could account for, indicating potential diffusion within the sediment. Given the greater sedimentation rates in Lake Erie, it was hoped to observe in greater resolution changes since the mid-1990s. However, though some decrease was observed at some locations the results are not clear. Many cores in Lake Erie had clearly observable gas voids, indicative of gas ebullition activity due to biogenic production, there were also observable mussel beds that could indicate mixing by bioturbation of core layers.

CO2-driven acidification and emerging contaminants, such as pharmaceuticals, pose new threats for the maintenance of natural populations of marine organisms by interfering with their normal biochemical pathways and defences. The combined effects of seawater acidification, as predicted in climate change scenarios, and an emerging contaminant (the non-steroidal anti-inflammatory drug, NSAID, diclofenac) on oxidative stress-related parameters were investigated in the Mediterranean mussel Mytilus galloprovincialis and the Manila clam Ruditapes philippinarum. A flow-through system was used to carry out a three-week exposure experiment with the bivalves. First, the animals were exposed to only three pH values for 7 days. The pH was manipulated by dissolving CO2 in the seawater to obtain two reduced pH treatments (pH −0.4 units and pH −0.7 units), which were compared with seawater at the natural pH level (8.1). Thereafter, the bivalves were concomitantly exposed to the three experimental pH values and environmentally relevant concentrations of diclofenac (0.00, 0.05 and 0.50 μg/L) for an additional 14 days. The activities of superoxide dismutase, catalase and cyclooxygenase, and lipid peroxidation and DNA strand-break formation were measured in both the gills and digestive gland after 7, 14 and 21 days of exposure to each experimental condition. The results show that the biochemical parameters measured in both the mussels and clams were more influenced by the reduced pH than by the contaminant or the pH*contaminant interaction, although the biomarker variation patterns differed depending on the species and tissues analysed. Generally, due to increases in its antioxidant defence, M. galloprovincialis was more resistant than R. philippinarum to both diclofenac exposure and reduced pH. Conversely, reduced pH induced a significant decrease in COX activity in both the gills and digestive gland of clams, possibly resulting in the increased DNA damage observed in the digestive gland tissue.

The problem of effective assessment of risk posed by complex mixtures of toxic chemicals in the environment is a major challenge for government regulators and industry. The biological effect of the individual contaminants, where these are known, can be measured; but the problem lies in relating toxicity to the multiple constituents of contaminant cocktails. The objective of this study was to test the hypothesis that diverse contaminant mixtures may cause a greater toxicity than the sum of their individual parts, due to synergistic interactions between contaminants with different intracellular targets. Lysosomal membrane stability in hemocytes from marine mussels was used for in vitro toxicity tests; and was coupled with analysis using the isobole method and a linear additive statistical model. The findings from both methods have shown significant emergent synergistic interactions between environmentally relevant chemicals (i.e., polycyclic aromatic hydrocarbons, pesticides, biocides and a surfactant) when exposed to isolated hemocytes as a mixture of 3 & 7 constituents. The results support the complexity-based hypothesis that emergent toxicity occurs with increasing contaminant diversity, and raises questions about the validity of estimating toxicity of contaminant mixtures based on the additive toxicity of single components. Further experimentation is required to investigate the potential for interactive effects in mixtures with more constituents (e.g., 50–100) at more environmentally realistic concentrations in order to test other regions of the model, namely, very low concentrations and high diversity. Estimated toxicant diversity coupled with tests for lysosomal damage may provide a potential tool for determining the toxicity of estuarine sediments, dredge spoil or contaminated soil.

As a result of human activities, climate forecasts predict changes in the oceans pCO₂ and salinity levels with unknown impacts on marine organisms. As a consequence, an increasing number of studies have begun to address the individual influence of pCO₂ and salinity but much remains to be done to understand their combined effects on the physiology and ecology of marine species. Our study addressed this knowledge gap by measuring the influence of current and predicted levels of pCO₂ (380 and 1200 ppm, respectively) and salinity (20, 25 and 30 psμ) on the energetic physiology of juvenile mussels (Mytilus chilensis) from the south-eastern Pacific region. Our results indicate that a reduced salinity caused a significant reduction in clearance rate, absorption efficiency and scope for growth of this species. Meanwhile, an increase in pCO₂ levels caused a reduction in excretion rates and interacted significantly with salinity in the rate of oxygen uptake measured in the mussel. These results suggest that potential changes in salinity might have a direct role on the physiology of M. chilensis. The effect of pCO₂, although less prevalent among the variables measured here, did interact with salinity and is also likely to alter the physiology of this species. Given the ecological and economic importance of M. chilensis, we call for further studies exploring the influence of pCO₂ across a wider range of salinities.

Glyphosate has been the most widely used herbicide worldwide over the last three decades, raising increasing concerns for its potential impacts on environmental and human health. Recent studies revealed that glyphosate occurs in soil, surface water, and groundwater, and residues are found at all levels of the food chain, such as drinking water, plants, animals, and even in humans. While research has demonstrated that glyphosate can induce a broad range of biological effects in exposed organisms, the global molecular mechanisms of action still need to be elucidated, in particular for marine species. In this study, we characterized for the first time the molecular mechanisms of action of glyphosate in a marine bivalve species after exposure to environmentally realistic concentrations. To reach such a goal, Mediterranean mussels Mytilus galloprovincialis, an ecologically and economically relevant species, were exposed for 21 days to 10, 100, and 1000 μg/L and digestive gland transcriptional profiles were investigated through RNA-seq. Differential expression analysis identified a total of 111, 124, and 211 differentially regulated transcripts at glyphosate concentrations of 10, 100, and 1000 μg/L, respectively. Five genes were found consistently differentially expressed at all investigated concentrations, including SERP2, which plays a role in the protection of unfolded target proteins against degradation, the antiapoptotic protein GIMAP5, and MTMR14, which is involved in macroautophagy. Functional analysis of differentially expressed genes reveals the disruption of several key biological processes, such as energy metabolism and Ca2+ homeostasis, cell signalling, and endoplasmic reticulum stress response. Together, the results obtained suggest that the presence of glyphosate in the marine ecosystem should raise particular concern because of its significant effects even at the lowest concentration.