Microplastics represent an emerging environmental issue and have been found almost everywhere including seafood, raising a great concern about the ecological and human health risks they pose. This study addressed the common technical challenges in the assessment of microplastics in seafood by developing an improved protocol based on Raman spectroscopy and using the green-lipped mussel Perna viridis and the Japanese jack mackerel Trachurus japonicus as the test models. Our findings identified a type of stainless-steel filter membranes with minimal Raman interference, and a combination of chemicals that achieved 99–100% digestion efficiency for both organic and inorganic biomass. This combined chemical treatment reached 90–100% recovery rates for seven types of microplastics, on which the surface modification was considered negligible and did not affect the accuracy of polymer identification based on Raman spectra, which showed 94–99% similarity to corresponding untreated microplastics. The developed extraction method for microplastics was further combined with an automated Raman mapping approach, from which our results confirmed the presence of microplastics in P. viridis and T. japonicus collected from Hong Kong waters. Identified microplastics included polypropylene, polyethylene, polystyrene and poly(ethylene terephthalate), mainly in the form of fragments and fibres. Our protocol is applicable to other biological samples, and provides an improved alternative to streamline the workflow of microplastic analysis for routine monitoring purposes.

Differences in the accumulation of mercury (Hg) in five species of marine bivalves, including scallops Chlamys nobilis, clams Ruditapes philippinarum, oysters Saccostrea cucullata, green mussels Perna viridis, and black mussels Septifer virgatus, were investigated. The bivalves displayed different patterns of Hg accumulation in terms of the body concentrations of methylmercury (MeHg) and total Hg (THg), as well as the ratio of MeHg to THg. Parameters of the biodynamics of the accumulation of Hg(II) and MeHg could reflect the species-dependent Hg concentrations in the bivalves. With the exception of black mussels, we found a significant relationship between the efflux rates of Hg(II) and the THg concentrations in the bivalves. The interspecific variations in the MeHg to THg ratio were largely controlled by the relative difference between the elimination rates of Hg(II) and MeHg. Stable isotope (δ¹³C) analysis indicated that the five bivalve species had contrasting feeding niches, which may also affect the Hg accumulation.

In the current study, we compared protein profiles in gills of Perna viridis after exposure to Prorocentrum lima, a dinoflagellate producing DSP toxins, and identified the differential abundances of protein spots using 2D-electrophoresis. After exposure to P. lima, the level of okadaic acid (a main component of DSP toxins) in gills of P. viridis significantly increased at 6 h, but mussels were all apparently healthy without death. Among the 28 identified protein spots by MALDI TOF/TOF-MS, 12 proteins were up-regulated and 16 were down-regulated in the P. lima-exposed mussels. These identified proteins were involved in various biological activities, such as metabolism, cytoskeleton, signal transduction, response to oxidative stress and detoxification. Taken together, our results indicated that the presence of P. lima caused DSP toxins accumulation in mussel gill, and might consequently induce cytoskeletonal disorganization, oxidative stress, a dysfunction in metabolism and ubiquitination/proteasome activity.

In this study, the aqueous uptake and dietary assimilation (trophic transfer) of two endocrine disrupting compounds (dioxin and phathalic acid) in the green mussel Perna viridis were quantified. During short-term exposure period, dioxin rapidly sorbed onto phytoplankton and its accumulation was much higher than that of phthalate. The uptake of these two compounds by the mussels increased with increasing temperature and salinity (for dioxin only). The dietary assimilation of the two contaminants was rather modest (10–64% for dioxin and 20–47% for phthalate), and was greatly dependent on the food species and concentration. Interestingly, dietary assimilation increased with increasing diatom food concentration. Gut passage time was partially responsible for the variable dietary assimilation. Given the high dissolved uptake rate and the modest dietary assimilation, aqueous exposure was predicted to be the dominant bioaccumulation source for both dioxin and phthalate in the green mussels under most conditions.

Tributyltin (TBT) is a toxic organotin compound that belongs to the group of Persistent Organic Pollutants (POPs) and it is documented to cause severe sexual disorders development in aquatic fauna. According to the present study, The TBT concentration in coastal water ranged from 303 ± 7.4 ngL⁻¹ to 25 ± 4.2 ngL⁻¹ wherein sediment was from 107 ± 4.1 ngKg⁻¹ to 17 ± 1.4 ngKg⁻¹. TBT in Perna viridis was found to range from 4 ± 1.2 ngKg⁻¹ to 42 ± 2.2 ngKg⁻¹ wet weight and in ascending order of the body weight. The highest TBT level in water and sediment was found in the Colombo port where the highest level of TBT in P. viridis (42 ± 2.2 ngKg⁻¹) was recorded from the Dikkowita fishery harbor. A positive correlation between the number of male P. viridis and TBT level (p < 0.05) suggests possible reproductive impairment in aquatic animals exposed continuously to a high concentration of TBT.

Microplastics (MPs) can be defined as small pieces of plastics that are less than five millimetres in diameter. MPs can be consumed and may be accumulated by filter-feeding organisms such as mussels. Therefore, this study aimed to determine the acute effects of different types, sizes and concentrations of artificially synthesized MPs on the mortality rate and MP accumulation of the green mussel Perna viridis. The samples were exposed to 66, 333, 666, and 1333 items/L of small MPs (<30 μm), medium MPs (30–300 μm), and large MPs (300–1000 μm) polystyrene (PS), polypropylene (PP), and polybutylene succinate (PBS) for 96 h. MPs accumulation in the soft tissue of mussels and mortality effects from MPs ingestion were assessed. There was no mortality observed in the control group. Small PP particles can lead to more mortality than PS and PBS particles of the same size. However, medium- and large PS caused a higher mortality percentage than the same size particles of PP and PBS. Large PS, PP, and PBS showed higher mortality potential than other sizes. MPs largely accumulated in the soft tissues rather than in gill tissues following the 96-hour exposure period. Increased accumulation of the three types of MPs was accompanied by an increase in the percentage of mussel mortality. The study highlights how particle size and type are key factors in plastic particulate toxicity.

Triazophos, as a lipophilic organophosphate pesticide, displays higher bioaccumulation in the gonads of shellfish. To study the reproductive toxicity of triazophos, we applied metabolomics to characterize the gender-specific metabolic responses in mussel Perna viridis exposed to triazophos. Metabolites were differently altered by triazophos in ovaries of mussel at different concentrations and time intervals, while basically similar metabolic response patterns were observed in male mussels at the two tested concentrations after exposure for 24 and 48h. The significant changes of metabolites in ovaries of mussel exhibited the disturbances in energy metabolism and osmotic regulation, while in male samples triazophos only affected the energy metabolism. Moreover, glycine, sn-glycero-3-phosphocholine, ethanol, aspartate, etc. exhibited consistent variation tendency in both male and female individuals. While the changes of homarine, betaine, taurine, hypotaurine, malonate, β-alanine, succinate, and choline showed obviously gender-specific responses. Overall, this study confirmed the gender-specific responses in gonad of P. viridis to triazophos exposure.

This study report the impact of heavy metals on cytopathology and DNA damage in the gills and hepatopancreas of Perna viridis collected from Ennore estuary and the Kovalam coastal waters. Principal Component Analysis (PCA) showed significant differences among all variables at the scale of plots. The ultrastructural alterations such as lack of microvilli, distorted mitochondria, electron dense particles and the presence of large mucous droplets were common in the gill and hepatopancreatic cells of mussels from Ennore estuary. However, the gill and hepatopancreatic cells of P. viridis from Kovalam revealed normal compartmentalization of cells. The percentage of tail DNA in the mussels from Ennore estuary was recorded as 12.44 and 10.14% in the gills and hepatopancreas respectively. Overall, it has been demonstrated that the Comet and cytopathological assays are useful biomarkers to assess the level of pollution and it provide reliable information on ecotoxicology and genotoxicology of coastal waters.

The nutrient uptake and release by the mussels in relation with amount of food consumption are emphasised in this research. Results of the study demonstrate that about 16% of the total mass dry weight food consumed by the mussels was released as faeces. The depositions of particulate carbon, nitrogen, and phosphorus in mussel faeces were found to be 26.3, 5.7, and 0.6mg/day/indv respectively. Soluble inorganic nutrients such as NH4+-N (2.5mg/day/indv), and PO43−-P (0.6mg/day/indv) were also released as mussel excretion. The nutrient absorption efficiency for the green mussel body was found to be 65.1% for carbon, 62.1% for nitrogen, and 79.2% for phosphorus. Subsequently, green mussels can remove particulate carbon, nitrogen and phosphorus at 108.1, 13.5, and 4.6mg/day/indv from aquatic systems. Finally, the results can help in estimating the carrying capacity of mussel cultivation without deteriorating the water quality in marine ecosystems.

This study investigates green mussel filtration rates based on variation of the mussel size and density, and attempts to correlate these with the amount of Chaetoceros calcitrans consumed by kinetic modeling. The filtration rates were found to be more effective in small mussels and with greater volumes of seawater/mussel which represent low mussel densities in the mussel farms. Under field condition, the first order kinetic model is useful for evaluation of mussel filtration rate. However, the composite exponential kinetic model was determined to better describe filtration rates in a close system. Higher ratios of seawater volume L/g DW mussel tissue, resulted in an increasing filtration rate until a maximum plateau was reached at 10.37L/h/g DW tissue as determined by first order kinetics. Based on the filtration rate, carbon, nitrogen, and phosphorus uptake by green mussels were found to be 2128.72, 265.41, and 66.67mg/year/indv, respectively.