Assessment of trace elements pollution in the sea ports of New South Wales (NSW), Australia using oysters as bioindicators

Human health risk attributed to consumption of seafood and recreation swimming in Negombo Lagoon, Sri Lanka: An assessment on lagoon water and inhabitant oysters (Crassostrea cucullata Born, 1778)

The Negombo Lagoon is a coastal lagoon influenced by local communities that introduce waste into its ecosystem. This study examined seven sewage entry points, out of which five sites were chosen for oyster sampling based on availability. Physicochemical and microbiological parameters of water (measured in triplicate at each site, n = 84) and oyster samples (total length, TL > 6 cm, n = 30) were assessed. Variation in regional coliform contamination was analyzed employing a one-way analysis of variance (ANOVA). Results indicated that the northern part of the lagoon exceeded recommended coliform thresholds for swimming (total coliform concentration (TCC) < 126 most probable number (MPN)) and seafood consumption (TCC < 100 MPN/g), indicating the presence of Escherichia coli. Water quality indices affirmed fecal pollution, except in the southern part of the lagoon. Furthermore, the study found high oyster consumption (76.7 %), elucidating that oysters from the northern part of Negombo Lagoon pose health risks.

The French Mussel Watch Program reveals the attenuation of coastal lead contamination over four decades

The mid-20th century industrial peak caused severe global lead (Pb) marine contamination. Although Europe initiated Pb emission reduction regulations in the 1980s, the short- and long-term impacts remain unclear. This study investigates the evolution of Pb contamination on the French coast through elemental and isotope analysis in oysters and mussels from the French "Mussel Watch" Program. Observations at 114 monitoring stations over four decades have shown decreasing Pb levels in these bivalve mollusks. In 1988, 95 % exceeded the background reference values; this level had dropped to 39 % by 2021. The Pb isotope ratios in bivalves from eight target sites revealed a reduction in bioaccumulated anthropogenic Pb, albeit without complete elimination. The long residence time of legacy Pb combined with inputs from diffuse urban sources likely explains the persistent presence of anthropogenic Pb on the French coast. This study endorses the importance of continuous biomonitoring to evaluate environmental regulations and policies.

Bioaccumulation of estuarine pollutants in leaf oysters (Isognomon ephippium) on the mid-north coast, New South Wales, Australia

Filter feeding bivalves are useful bioindicators for the detection of biologically available pollutants. We investigated trace metals, metalloids, and pesticides in leaf oyster (Isognomon ephippium) soft tissue and shells and compared them to sediment in five estuaries in northern New South Wales, Australia. Concentrations of Pb, Cr, Mn, Ni, Fe and Al were higher in sediments, whereas Zn, Cd, Ag, Hg, Se and As bioaccumulated in the soft tissue. The amount of Cu, Hg and Ni in the sediment from Tweed and Richmond River estuaries exceeded the Australian national sediment quality guideline values. Only one pesticide, atrazine, was detected in leaf oyster soft tissue. Combinations of six elements in the soft tissue were the best predictors of oyster condition index and shell size, whereas sediment contaminants showed weak relationships. Overall, the bioaccumulation of metals and metalloids increases with leaf oyster size and reduces leaf oyster condition, suggesting these large bivalves are useful bioindicators for pollution in estuarine environments.

Characterization of trace elements in thermal and mineral waters of Greece

Natural thermal and mineral waters are widely distributed along the Hellenic region and are related to the geodynamic regime of the country. The diverse lithological and tectonic settings they are found in reflect the great variability in their chemical and isotopic composition. The current study presents 276 (published and unpublished) trace element water data and discusses the sources and processes affecting the water by taking into consideration the framework of their geographic distribution. The dataset is divided in groups using temperature- and pH-related criteria. Results yield a wide range of concentrations, often related to the solubility properties of the individual elements and the factors impacting them (i.e. temperature, acidity, redox conditions and salinity). Many elements (e.g. alkalis, Ti, Sr, As and Tl) present a good correlation with temperature, which is in cases impacted by water rock interactions, while others (e.g. Be, Al, Cu, Se, Cd) exhibit either no relation or an inverse correlation with T possibly because they become oversaturated at higher temperatures in solid phases. A moderately constant inverse correlation is noticed for the vast majority of trace elements and pH, whereas no relationship between trace element concentrations and Eh was found. Seawater contamination and water-rock interaction seem to be the main natural processes that influence both salinity and elemental content. All in all, Greek thermomineral waters exceed occasionally the accepted limits representing in such cases serious harm to the environment and probably indirectly (through the water cycle) to human health.

Metal Biological Enrichment Capacities, Distribution Patterns, and Health Risk Implications in Sea Bass (Lateolabrax japonicus)

Seabass (Lateolabrax japonicus) is a major aquacultured fish species worldwide. The bioconcentration, bioaccumulation, and biomagnification of metals in water, sediments, and commercial feed were investigated in L. japonicus from an aquaculture pond in the Pearl River Delta of South China. Aluminum (Al), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), and lead (Pb) were determined in the dorsal muscle, viscera, backbone, gill, and stomach contents of L. japonicus. The gill and stomach contents had higher levels of bioconcentration of most metals than other parts of fish. Based on the bioaccumulation factor, the gill and backbone exhibited the highest accumulation of Zn, while the viscera had the highest capacity to accumulate Cu. The mean biomagnification factor values exceeded for As in dorsal muscle, for Cu in the viscera, for Cr and Pb in the gill, and for Al, Cr, Fe, Cu, and Pb in the stomach contents, indicating efficient bioaccumulation from commercial feed and their habitat. Non-metric multidimensional scaling analysis revealed two groups that resulted from the accumulation of metals in various parts of L. japonicus. Moreover, health risk assessment indicated that no notable adverse health effects occurred from the ingestion of L. japonicus.

Evaluation of metal contamination in surface sediments and macroalgae in mangrove and port complex ecosystems on the Brazilian equatorial margin

This study evaluated metal contamination in surface sediments and macroalgae of mangroves and port complexes on the Brazilian equatorial margin. Samples were collected between August 2020 and February 2021 at seven points in a mangrove swamp under the influence of port activity and at two points without port activity. Metal concentrations in the macroalgae and sediments were determined using inductively coupled plasma‒optical emission spectrometry. All macroalgal species bioaccumulated metals, as demonstrated by their bioaccumulation factors. The geochemical contamination indices indicated that the estuarine complex was influenced by port activity as moderately contaminated by Pb, Cr, Mn, and Fe and considerably contaminated by Zn and Cu. The enrichment factor confirmed significant mineral enrichment of Zn and Cu in this environment. The concentrations of the metals in the sediment followed the order Fe > Mn > Cr > Zn > Cu > Pb at most sampling points. Cladophoropsis membranacea recorded the highest bioaccumulation values for Pb (0.44), Rhizoclonium africanum for Zn (1.08), Cr (0.55), and Fe (0.30), and Bostrychia radicans for Mn (2.22). The bioaccumulation pattern of metals in the most abundant macroalgal species followed the order Bostrychia radicans (Mn > Zn > Cu > Cr > Pb > Fe) and Rhizoclonium africanum (Zn > Mn > Cr > Cu > Pb > Fe).

Bioaccumulation and human health implications of trace metals in oysters from coastal areas of China

This study recompiled a national dataset to characterize the pollution level and health risk of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) in oysters along the coastal areas of China. Results showed that the median concentrations of Cd, Cu, Pb and Zn in nationwide oysters were 5.5, 335, 1.3 and 1280 mg/kg dry weight, respectively. Generally, oysters from the north coasts presented lower metal pollution and higher quality than those from the south. The regional characteristics of trace metals in oysters might be contributed by the interspecific differences. Nationally, the noncarcinogenic risk posed by these four metals in oysters was relatively low, with the risk only occurring in a few hotspots such as the Pearl River Estuary and the Jiulong River Estuary. However, more attention should be paid to the carcinogenic risk of Cd, and priority should be given to formulating control measures to mitigate Cd pollution.

Exposure to multiple elements reduces the health of Saccostrea glomerata: An assessment of the Richmond River estuary, NSW, Australia

This study investigated relationships between Sydney Rock Oyster (SRO) health and element concentrations in sediments and oysters from the Richmond River estuary. Six sites were sampled between November 2019 and May 2020. Multivariate permutational analysis of variance was used to compare oyster health parameters and element concentrations between sites, wet and dry conditions, and in oyster and sediment samples. Statistical analysis revealed significant spatial differences in oyster mortality, condition index, and size. Metal concentrations in oyster flesh significantly differed from metals in sediments. Most metals in sediments were below guideline values, except for Ni at some sites. Mortality, condition index, and weight correlated negatively with individual elements in oyster flesh (P, Zn, Mg, Al, Ni). BEST statistical models included various combinations of metals in sediment and flesh. This study highlights that spatial differences in SRO health tend to be related to site-specific metal compositions in sediment and oysters.

Seasonal variations and human health risk assessment of trace elements in the bivalve ecosystem in the Sea of Marmara

Twelve trace elements were studied in four economically important bivalve molluscs (Mediterranean mussel, manila clam, striped venus clam, and truncated wedge clam) from the southern Marmara Sea for seasonal bioaccumulation and human health risk assessment. According to the findings, Fe and Zn were the most accumulative and element concentrations changed considerably (P < 0.05) between seasons and species. Daily, weekly, monthly intake and target hazard quotients of the trace elements were estimated and compared with maximum limits. The results revealed that consuming these bivalve molluscs from the southern Marmara Sea could be considered safe for human consumption. Nevertheless, further monitoring is needed in order to better follow the development in time of elemental pollution due to increasing environmental pressure on the Marmara Sea basin, together with research on other different bioaccumulative organisms.

Source and Distribution of Emerging and Legacy Persistent Organic Pollutants in the Basins of the Eastern Indian Ocean

Persistent organic pollutants (POPs) have received significant and ongoing attention. To establish favorable regulatory policies, it is vital to investigate the occurrence, source, and budgets of POPs worldwide. POPs including phthalic acid esters (PAEs), organophosphate esters (OPEs), brominated flame retardants (BFRs), and highly chlorinated flame retardants (HFRs) have not yet been examined in the Eastern Indian Ocean (EIO). In this study, the distribution of POPs has been investigated from surface sediments with the depth of 4369-5742 m in the Central Indian Ocean Basin (CIOB) and Wharton Basin (WB) of EIO. The average (±SD) concentrations of ∑₁₁PAEs, ∑₁₁OPEs, ∑₄ BFRs, and ∑₅HFRs were 1202.0 ± 274.36 ng g^-1 dw, 15.3 ± 7.23 ng g^-1 dw, 327.6 ± 211.74 pg g^-1 dw, and 7.9 ± 7.45 pg g^-1 dw, respectively. The high abundance of low-molecular-weight (LMW) PAEs, chlorinated OPEs, LMW BDEs, and anti-Dechlorane Plus indicated the pollution characteristics in the EIO. Correlation analysis demonstrated that LMW compounds may be derived from the high-molecular-weight compounds. The monsoon circulation, currents, and Antarctic Bottom Water may be the main drivers. POP accumulation rate, depositional flux, and mass inventory in the Indian Ocean were also estimated.

Assessment of microplastic and trace element pollution in the southeastern Mediterranean coasts, Egypt, using shellfish Arca noae as a bioindicator

The ubiquitous presence of microplastics (MPs) and trace elements in the marine environment is regarded as a global threat to marine organisms. The current study aims to assess MP levels and trace element (Cu, Zn, Cd, Pb, Se, and Fe) accumulation in the shellfish Arca noae collected from five locations along the southeastern Mediterranean coasts, Alexandria, Egypt. The frequency of the occurrence of ingested MPs in A. noae soft tissues was 48%, whereas the abundance of MPs was 1.65 ± 0.28 MP/individual and 0.58 ± 0.04 items g¹ of the wet weight of tissue. Polyethylene was the most abundant polymer in A. noae, followed by polypropylene and polystyrene. The concentration levels of Zn, Cd, and Pb detected in the soft tissues of A. noae are higher than the maximum permissible limits. This study provides baseline data for further environmental assessments, with the use of A. noae as an early warning indicator in biomonitoring programs.

Oyster arsenic, cadmium, copper, mercury, lead and zinc levels in the northern South China Sea: long-term spatiotemporal distributions, combined effects, and risk assessment to human health

Estuarine and coastal ecosystems are often considered vulnerable due to the complex biogeochemical processes and the human disturbances through a variety of pollution. Among environmental contaminants, heavy metals in estuarine and coastal ecosystems have been of increasing concern in environmental conservation. Long-term exposure to heavy metal contamination, mainly through food and water, could be harmful to human health. It is therefore critical to understand the quantitative comparisons and combined effects of different heavy metals in common seafood species, such as oysters. This work studied the long-term spatiotemporal trends and health risk assessment of oyster arsenic (As), cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn) levels in the coastal waters of northern South China Sea. Cultured oysters (Crassostrea rivularis) from 23 estuaries and harbors in the coastal areas of northern South China Sea in 1989-2015 were analyzed for the spatiotemporal trends of the six heavy metal levels. Metal pollution index (MPI), target hazard quotient (THQ), and hazard index (HI) were used for quantifying the exposure of the six heavy metals to human health through oyster consumption. Principal component analysis (PCA) was used for assessing the relative importance of the six metals in oyster heavy metal distribution patterns in the northern South China Sea. Overall, the As, Cd, Cu, Hg, Pb, and Zn levels in oysters from the northern South China Sea generally declined from 1989 to 2015, stayed relatively high (MPI = 2.42-3.68) during 1989-2000, gradually decreased since 2000, and slightly increased after 2010. Oyster heavy metal levels were highest in the Pearl River Estuary (MPI = 1.20-5.52), followed by west Guangdong and east Guangdong, Guangxi, and Hainan coastal waters. This pattern is probably because economics and industry around the Pearl River Estuary have been growing faster than the other areas of this work in the recent two decades, and it should be taken as a hotspot for the monitoring of seafood safety in southern China. Principal component analysis indicated that Cu, Zn, and Cd were the most important metals in the long-term distributions of oyster heavy metal levels in the northern South China Sea. Health risk assessment suggested that the risk of the six heavy metals exposure through oyster consumption were relatively high during 1989-2005 (THQ = 1.01-5.82), significantly decreased since 2005 (THQ < 1), and slightly increased after 2010.

A nationwide survey of trace metals and Zn isotopic signatures in mussels (Mytilus edulis) and oysters (Crassostrea gigas) from the coast of South Korea

Thirteen trace metals and Zn isotopic signatures were investigated in mussels and oysters collected from the coast of South Korea to evaluate their bioavailability in bivalve mollusks. The average Cu, Zn, and Cd concentrations were 2.6-17.7 times higher in oysters than mussels, and high biota sediment accumulation factors (>30) were observed for these metals in oysters. Except for Pb in mussels, most metals had no correlation with total sediment concentrations. In oysters, Fe, V, Cu, Zn, Sn, and Pb concentrations were significantly correlated with sediments. The average values of δ⁶⁶Zn_IRMM3702 in mussels, oyster, and sediments were +0.09‰, +0.12‰, and -0.06‰, respectively. Soft tissues of mussels and oysters with high Zn concentrations tended to contain lighter Zn isotopes. The results indicate that oysters are a better biomonitoring organism for metal contamination than mussels and can be used in the monitoring and management of coastal environments and ecosystems.

Spatial and temporal distribution of trace elements in Padina pavonica from the northern Adriatic Sea

Chemical pollution is a major environmental concern especially in coastal areas, having adverse impacts on marine organisms and ecosystem services. Macroalgae can accumulate trace elements, but available studies are restricted to a limited number of elements and species. The goal of this research was to assess, seasonally, the concentrations of 22 elements in the brown alga Padina pavonica from monitoring sampling sites in Slovenian waters. The concentration of most elements in thalli differed significantly between spring and autumn, with generally higher levels in autumn samples. However, it was not possible to correlate these concentrations with the ecological status of macroalgae. The maximum values set by European regulations for the potentially hazardous As, Cd and Hg in food and feed were never exceeded, while Pb concentrations were slightly higher. The results show that P. pavonica can act as an effective bioindicator of chemical pollution.

Elemental composition of whole body soft tissues in bivalves from the Bijagós Archipelago, Guinea-Bissau

Marine bivalves are bioindicators of coastal environmental pollution, integrating monitoring programs worldwide. Nonetheless, the choice of particular species as an indicator requires validation, achieved by understanding the differences in element concentrations among and within species. The present study compares the chemical composition of whole body soft tissues of four common bivalve species from the Bijagós Archipelago, a pristine region of West Africa. Significant differences were recorded in the concentrations of various elements among studied species, which likely arise from species-specific uptake and bioaccumulation processes. Overall, there was a segregation between a group including the bloody cockle Senilia senilis and oyster Crassostrea tulipa (with high Cd and Zn concentrations) versus the two other species, Austromacoma nymphalis (with low Cu and high Mn, Se, Hg, Pb concentrations) and Diplodonta spp. (with high values of Cu, Al, Fe, V, Cr, Hg, Pb). C. tulipa was sampled in two different substrates (rock beds and mangrove roots), and the two groups revealed different chemical profiles, with significantly higher concentrations of P, Si, Zn and Cr and lower Cu in specimens fixed in mangrove roots. These results strongly suggest the influence of small-scale environmental variability on the accumulation of particular elements. We found extremely high Cd concentrations in S. senilis (27.1 ± 7.53 μg g^-1 DW) and identified C. tulipa as another high Cd-accumulating species (ca. 10 μg g^-1 DW). Our results suggest a detoxifying mechanism linked with the presence of Se to reduce the potential toxic effects of Cd in these two species. Cadmium concentrations reported for some bivalve species in this area largely exceed the maximum values proposed by the European Union, emphasizing the need for a regular contamination assessment.

Assessing the ecological quality status of the highly polluted Bagnoli area (Tyrrhenian Sea, Italy) using foraminiferal eDNA metabarcoding

Morphology-based benthic foraminifera indices are increasingly used worldwide for biomonitoring the ecological quality of marine sediments. The recent development of foraminiferal eDNA metabarcoding offers a reliable, time-, and cost-effective alternative to morphology-based foraminiferal biomonitoring. However, the practical applications of these new tools are still highly limited. In the present study, we evaluate the response of benthic foraminifera and define the ecological quality status (EcoQS) in the Bagnoli area (Tyrrhenian Sea, Italy) based on a traditional morphology-based approach and eDNA metabarcoding. The geochemical data show that several sites in front of the former industrial plant contain higher concentrations of potentially toxic elements than the effect range median and are characterized by the highest total organic carbon (TOC) content, whereas the distantly located sites can be considered relatively low- to unpolluted. Significant differences (i.e., diversity and assemblage composition) in both morphological and molecular datasets were found between the relatively low- to unpolluted and the most polluted areas. Similarly, the selected ecological indices of both morphological and molecular datasets strikingly and congruently resulted in a clear separation following the environmental stress gradient. The molecular indices (i.e., g-exp(H'_bc), g-Foram AMBI, and g-Foram AMBI-MOTUs) reliably identified poor-to-bad EcoQS in the polluted area in front of the former industrial plant. On the other hand, the Foram-AMBI based on morphology well identified an overall trend but seemed to overestimate the EcoQS if the traditional class boundaries were considered. The congruent and complementary trends between morphological and metabarcoding data observed in the case of the Bagnoli site further support the application of foraminiferal metabarcoding in routine biomonitoring to assess the environmental impacts of heavily polluted marine areas.

Biochemical responses of oysters in evaluating environmental quality of tropical Indian estuarine systems

Impact of varying concentrations and counts of toxic metals and indigenous bacteria on antioxidative defense system in edible oyster, Saccostrea cucullata, collected from four tropical estuarine systems of Goa (west coast of India), are presented in this study. Relatively high abundance of bacteria was estimated from the oysters especially during monsoon season (June-September). Density of total and fecal coliforms were about 24 times higher in the organism than the surrounding water (average TC: 4360 and FC: 3475 MPN 100 ml^-1). Sedimentary Cd, Pb, and Hg concentrations varied from 0.12 to 0.48, 19.28-102.48, and 0.03-0.13 mg kg^-1 (dry wt.) while, bioaccumulation of Cd, Pb, and Hg in the oysters ranged from 5.17 to 10.6, 0.18-7.99, and 0.06-0.22 mg kg^-1 (dry wt.) respectively. Higher degree of pollution and moderate ecotoxicological risks with increasing toxicity (36-37%) was observed in two of the tropical estuaries. Biomarker response in the oysters was somewhat inconsistent with pollution load in the estuarine systems. Elevated environmental stress was observed during pre-monsoon (March-May) followed by the monsoon period. Sedimentary metals were identified as predominant inducers of antioxidative defence system in oysters from the study areas. This study suggests that, biomarker can be useful in assessing the combined effects of metal and bacterial contaminations on native oysters and in evaluating environmental quality in tropical estuarine systems.

Accumulation of different metals in oyster Crassostrea gigas: Significance and specificity of SLC39A (ZIP) and SLC30A (ZnT) gene families and polymorphism variation

The Zrt/Irt-like proteins (ZIP, SLC39A) and zinc transporters (ZnT, SLC30A) are the two major gene families responsible for the import/export of Zn and other metals. In this study, the mRNA expression levels and genetic variations of eight ZnTs and 14 ZIPs were identified in Crassostrea gigas after exposure to Zn, Cd, Cu, Hg, and Pb. Metal exposure induced reactive oxygen species (ROS) and malondialdehyde (MDA) accumulation and antioxidant enzyme expression. The expanded gene numbers of superoxide dismutase (SOD) in the oysters exhibited diverse expression under exposure to the five metals, and the contrasting expressions of both ZnTs and ZIPs under different metal exposures were observed, revealing their ion-specific responses. Zn and Cu have similar transporters and induce high expression levels of ZnT1, 2, 7, and 9 and ZIP1, 3, 6, 9, 10, 11, and 14. Pb induced high expression levels of ZIP7, and 13 and ZnT5, 6, and 7, which are mainly expressed in the endoplasmic reticulum (ER). Cd induced high expression levels of ZnT1, 2, and 7 and ZIP1, 6, 9, 10, 11, and 13. Hg exposure was found to have little effect on the ZIP and ZnT expression levels. Based on 3784 single nucleotide polymorphisms (SNPs) within the ZnTs and ZIPs, genetic association analysis for Zn accumulation was conducted on 427 oyster samples. The 38 SNPs, which were located within 12 genes, were identified to be associated with Zn content (p < 0.01), explaining the phenotypic variation from 1.61% to 3.37%. One nonsynonymous mutation and related haplotypes were identified within ZIP1, explaining 1.69% of the variation in Zn. Its high expression under Zn exposure revealed its important role in Zn transportation. To the best of our knowledge, this study is the first comprehensive investigation of the transportation mechanisms of ZIPs and ZnTs under different metal exposures and the genetic effect of Zn accumulation in oysters, and provides valuable biomarkers and genetic resources to evaluate environmental metal pollution.

Level of Contamination Assessment of Potentially Toxic Elements in the Urban Soils of Volos City (Central Greece)

A three-year study, designed to record the level of potentially toxic elements within the urban complex in the city of Volos, Greece, was carried out between 2018 and 2020. For the needs of the aforementioned study, 62 surface (0–15 cm) soil samples were collected each year (i.e., 186 samples in total) from an urban area of 3.65 km2, and the average value of pseudo-total metal concentration was measured. Soil pollution indices, such as the contamination factor (CF) and the geo-accumulation index (Igeo), were estimated regarding each of the metals of interest. The respective thematic maps were constructed, and the spatial variability of the contamination degree was displayed. Higher values of the CF and Igeo were obtained near the heavy traffic roads and beside the railway station, the bus stations, and the commercial port. The maps based on the pollution indices, along with the database that was constructed using the appropriate mathematical tools of geostatistical analysis, may be a useful tool for monitoring, prediction, and continuous verification of contamination in the urban soils of Volos city.

Bioaccumulation of trace metals and speciation of copper and zinc in Pacific oysters (Crassostrea gigas) using XANES/EXAFS spectroscopies

Copper (Cu) and zinc (Zn) concentrations in oyster soft tissues can be particularly high due to contamination, leading to extremely green/blue colors. This raises key questions regarding the behavior and speciation of trace metals in oyster soft tissues. This study investigated trace metal concentration profiles of contaminated Pacific oyster (Crassostrea gigas) soft tissues collected from trace metal-contaminated coastal area of Xiangshan District using inductively coupled plasma optical emission spectrometry (ICP-OES), energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Moreover, Cu and Zn speciation in contaminated and non-contaminated oyster soft tissues were investigated by X-ray absorption near edge structure spectroscopy/extended X-ray absorption fine structure (XANES/EXAFS) spectroscopic methods. The contents of Cu (1,100-1,400 mg/kg) and Zn (500-700 mg/kg) dry weight were high in oyster soft tissue samples. The XANES/EXAFS results revealed that Cu and Zn existed primarily as copper (II) oxide (CuO) and zinc oxide (ZnO) in contaminated oysters. Furthermore, Cu and Zn formed clusters with Cu-O and Zn-O interatomic distances of 1.97 and 2.21 Å, (coordination numbers 1.0 and 5.6), respectively. In non-contaminated oysters, the less abundant Cu and Zn existed mainly as copper(I) sulfide (Cu₂S) and zinc sulfide (ZnS) forming clusters with Cu-S and Zn-S (thiolates) bond distances of 2.09 and 1.23 Å (coordination numbers of 4.6 and 2.4). These results provide further understanding on the chemical speciation of Cu and Zn in contaminated and non-contaminated oyster soft tissues as well as the bioaccumulation of trace metals in the oyster soft tissues.

Interrelationship of microplastic pollution in sediments and oysters in a seaport environment of the eastern coast of Australia

Since the middle of the twentieth century, microplastics have emerged as a pollutant of concern. Sea ports are recipients of large amount of discharges through ballast water, ship traffic and other commercial activities, which may additionally add to the overall marine microplastic pollution. The aim of this study was to determine the interrelationship of microplastic pollution in the sediments and oysters at six major seaports (Port Jackson, Botany, Kembla, Newcastle, Yamba and Eden) of New South Wales (NSW). The results revealed the significant abundance of microplastic particles both in sediments and oysters in all the studied seaports which were estimated to be around 83-350 particles/kg dry weight in the sediments and 0.15-0.83 particles/g wet weight in the oysters. Although, the abundance of microplastics showed similar pattern in the sediments and oysters of the studied seaports, oysters had higher number of microplastics than sediments in all sea ports. Moreover, the results showed that the shapes, size and colours in the oysters did not necessarily match the main components in the sediments, although the polymer types matched well between each other. Black fibres between 0.1mm-0.5mm in size were the most abundant microplastics in oysters, whereas white spherules between 0.5mm-1mm in size were dominant in the sediments of NSW seaports. Moreover, the analysis of variance between microplastic abundance in sediment and oysters showed a non-significant positive linear relationship. Fourier Transform Infrared analysis further indicated that both sediments and oysters contained microplastics with two main polymers, polyethylene terephthalate and nylon, which suggests that the abundance of microplastics in the study ports was highly influenced by the port activities, mainly the intensive commercial fishing and fish processing activities along with intensive anthropogenic and industrial activities inside and surroundings the port environments.