From antioxidant defense to genotoxicity: Deciphering the tissue-specific impact of AgNPs on marine clam Ruditapes philippinarum.

The escalating use of silver nanoparticles (AgNPs) across various sectors for their broad-spectrum antimicrobial capabilities, has raised concern over their potential ecotoxicological effects on aquatic life. This study explores the impact of AgNPs (50 µg/L) on the marine clam Ruditapes philippinarum, with a particular focus on its gills and digestive glands. We adopted an integrated approach that combined in vivo exposure, biochemical assays, and transcriptomic analysis to evaluate the toxicity of AgNPs. The results revealed substantial accumulation of AgNPs in the gills and digestive glands of R. philippinarum, resulting in oxidative stress and DNA damage, with the gills showing more severe oxidative damage. Transcriptomic analysis further highlights an adaptive up-regulation of peroxisome-related genes in the gills responding to AgNP-induxed oxidative stress. Additionally, there was a noteworthy enrichment of differentially expressed genes (DEGs) in key biological processes, including ion binding, NF-kappa B signaling and cytochrome P450-mediated metabolism of xenobiotics. These insights elucidate the toxicological mechanisms of AgNPs to R. philippinarum, emphasizing the gill as a potential sensitive organ for monitoring emerging nanopollutants. Overall, this study significantly advances our understanding of the mechanisms driving nanoparticle-induced stress responses in bivalves and lays the groundwork for future investigations into preventing and treating such pollutants in aquaculture.

Seawater quality criteria and ecotoxicity risk assessment of zinc oxide nanoparticles based on data of resident marine organisms in China.

Water quality criteria (WQC) for zinc oxide nanoparticles (ZnO NPs) are crucial due to their extensive industrial use and potential threats to marine organisms. This study conducted toxicity tests using marine organisms in China, revealing LC50 or EC50 values for ZnO NPs ranging from 0.36 to 95.6 mg/L across seven species, among which the salinity lake crustacean zooplankton Artemia salina exhibited the highest resistance, while diatom Phaeodactylum tricornutum the most sensitive. Additionally, the EC10 or maximum acceptable toxicant concentration (MATC) values for ZnO NPs were determined for five species, ranging from 0.03 to 2.82 mg/L; medaka Oryzias melastigma demonstrated the highest tolerance, while mysis shrimp Neomysis awatschensis the most sensitive. Based on the species sensitivity distribution (SSD) method, the derived short-term and long-term WQC for ZnO NPs were 138 µg/L and 8.37 µg/L, respectively. These values were further validated using the sensitive species green algae Chlorella vulgaris, confirming effective protection. There is no environmental risk observed in Jiaozhou Bay, Yellow River Estuary and Laizhou Bay in the northern coastal seas of China. This study provides important reference data for the establishment of water quality standards for nanoparticles.

Arsenate toxicity to the marine microalga Chlorella vulgaris increases under phosphorus-limited condition.

To understand the arsenic (As) toxicity to aquatic organisms in the phosphors-polluted aquatic ecosystem, the growth, the physiological response of Chlorella vulgaris exposed to As (V), and the underlying mechanism were investigated under different phosphorus (P) levels (0, 6, 13, 32 µM). Results showed that As toxicity to the marine microalga C. vulgaris was enhanced under P-limited condition. P supply distinctly altered the effect of As on the light-harvesting efficiency of photosystem. Insufficient P supply also resulted in an enhanced level of membrane integrity loss, which probably facilitated As entering cells and led to stronger toxicity to C. vulgaris under low P supply. At high concentrations of As, the relative superoxide dismutase (SOD) activity was significantly enhanced. When phosphorus was limited, the activation of peroxidase (POD) was significantly enhanced after adding As (V). When intracellular SOD activity was at its highest level, the level of membrane peroxidation (MDA) was also at the highest level, and membrane peroxidation level was positively related to the level of membrane integrity loss (Pearson R2=0.8977). These results suggested that alternation of light-harvesting efficiency of photosystem and As-induced oxidative damage, resulting in membrane peroxidation and integrity loss, were the possible mechanism of As toxicity to C. vulgaris. This study provided insight into the understanding of As toxicity to algae in the eutrophication aquatic system and the potential application of algae in As remediation.

Microbial communities across nearshore to offshore coastal transects are primarily shaped by distance and temperature.

Recent studies have focused on linking marine microbial communities with environmental factors, yet, relatively little is known about the drivers of microbial community patterns across the complex gradients from the nearshore to open ocean. Here, we examine microbial dynamics in 15 five-station transects beginning at the estuarine Piver's Island Coastal Observatory (PICO) time-series site and continuing 87 km across the continental shelf to the oligotrophic waters of the Sargasso Sea. 16S rRNA gene libraries reveal strong clustering by sampling site with distinct nearshore, continental shelf and offshore oceanic communities. Water temperature and distance from shore (which serves as a proxy for gradients in factors such as productivity, terrestrial input and nutrients) both most influence community composition. However, at the phylotype level, modelling shows the distribution of some taxa is linked to temperature, others to distance from shore and some by both factors, highlighting that taxa with distinct environmental preferences underlie apparent clustering by station. Thus, continental margins contain microbial communities that are distinct from those of either the nearshore or the offshore environments and contain mixtures of phylotypes with nearshore or offshore preferences rather than those unique to the shelf environment.

Conserved Microbial Toxicity Responses for Acute and Chronic Silver Nanoparticle Treatments in Wetland Mesocosms.

Most studies of bacterial exposure to environmental contaminants focus on acute treatments; however, the impacts of single, high-dose exposures on microbial communities may not readily be extended to the more likely scenario of chronic, low-dose contaminant exposures. Here, in a year-long, wetland mesocosm experiment, we compared microbial community responses to pulse (single 450 mg dose of silver) and chronic (weekly 8.7 mg doses of silver for 1 year) silver nanoparticle (Ag0 NP) treatments, as well as a chronic treatment of "aged" sulfidized silver nanoparticles (Ag2S NPs). While mesocosms exposed to Ag2S NPs never differed significantly from the controls, both Ag0 NP treatments exhibited reduced microbial diversity and altered community composition; however, the effects differed in timing, duration, and magnitude. Microbial community-level impacts in the acute Ag0 NP treatment were apparent only within the first weeks and then converged on the control mesocosm composition, while chronic exposure effects were observed several months after exposures began, likely due to interactive effects of nanoparticle toxicity and winter environmental conditions. Notably, there was a high level of overlap in the taxa which exhibited significant declines (>10×) in both treatments, suggesting a conserved toxicity response for both pulse and chronic exposures. Thus, this research suggests that complex, but short-term, acute toxicological studies may provide critical, cost-effective insights into identifying microbial taxa sensitive to long-term chronic exposures to Ag NPs.

Single and combined metal contamination in coastal environments in China: current status and potential ecological risk evaluation.

With the development of industrialization and urbanization, metal and metalloid pollution is one of the most serious environmental problems in China. Current contamination status of metals and metalloid and their potential ecological risks along China's coasts were reviewed in the present paper by a comprehensive study on metal contents in marine waters and sediments in the past few decades. The priority metals/metalloid cadmium (Cd), mercury (Hg), chromium (Cr), lead (Pb), and arsenic (As), which were the target elements of the designated project "Comprehensive Prevention and Control of Heavy Metal Pollution" issued by the Chinese government in 2011, were selected considering their high toxicity, persistence, and prevalent existence in coastal environment. Commonly used environmental quality evaluation methods for single and combined metals were compared, and we accordingly suggest the comprehensive approach of joint utilization of the Enrichment Factor and Effect Range Median combined with Pollution Load Index and Mean Effect Range Median Quotient (EEPME); this battery of guidelines may provide consistent, internationally comparable, and accurate understanding of the environment pollution status of combined metals/metalloid and their potential ecological risk.

Organic matter modifies biochemical but not most behavioral responses of the clam Ruditapes philippinarum to nanosilver exposure.

Adsorption of dissolved organic matter (DOM) can alter the environmental fate, bioavailability and toxicity of silver nanoparticles (Ag NPs). However, a number of questions remain about DOM's ability to modify nanotoxicity. Here, we examine the impact of humic acid (HA, as a model DOM) on the toxicity of Ag NPs (10 µg L-1) in the marine clam Ruditapes philippinarum. Results showed that DOM additions to Ag NP treatments reduce clam silver tissue burdens and the oxidative stress response. However, HA does not significantly affect the impact of Ag NPs on clam acetylcholinesterase activity and feeding behavior (measured as filtration rate). Overall, the integrated biological response index supports the conclusion that humic acid reduces the toxicity of Ag NPs, clearly indicating the importance of considering environmental factors when assessing potential risks posed by nanomaterials in natural settings.

Trace elements distribution and ecological risk assessment of seawater and sediments from Dingzi Bay, Shandong Peninsula, North China.

Selected trace elements (Hg, As, Pb, Cu, Cd, Cr and Zn) in seawater and sediments from Dingzi Bay, a semi-enclosed bay suffering from severe degradation located in the Shandong Peninsula, were investigated to evaluate the spatial distribution and potential ecological risk. Results indicated that higher concentrations occurred in the inner bay. Calculation of pollution load index (PLI) showed overall low values while the concentration factor (CF) indicated that Hg, As and Cd were at moderate risk levels in the region. Based on the effects-range classification, As was likely to pose environment risk. Principal component analysis (PCA) revealed that in addition to background contributions, the trace elements contamination could also be affected by anthropogenic pollution sources. The results of present study provide useful background information for further marine investigation and management in the region.

Fate and effects of metal-based nanoparticles in two marine invertebrates, the bivalve mollusc Scrobicularia plana and the annelid polychaete Hediste diversicolor.

The objective of this paper is to synthesize results from seven published research papers employing different experimental approaches to evaluate the fate of metal-based nanoparticles (Ag NPs, Au NPs, CuO NPs, CdS NPs, ZnO NPs) in the marine environment and their effects on two marine endobenthic species, the bivalve Scrobicularia plana and the ragworm Hediste diversicolor. The experiments were carried out under laboratory (microcosms) conditions or under environmentally realistic conditions in outdoor mesocosms. Based on results from these seven papers, we addressed the following research questions: (1) How did the environment into which nanoparticles were released affect their physicochemical properties?, (2) How did the route of exposure (seawater, food, sediment) influence bioaccumulation and effects?, (3) Which biomarkers were the most responsive? and (4) Which tools were the most efficient to evaluate the fate and effects of NPs in the marine environment? The obtained results showed that metal-based NPs in general were highly agglomerated/aggregated in seawater. DGT tools could be used to estimate the bioavailability of metals released from NPs under soluble form in the aquatic environment. Both metal forms (nanoparticulate, soluble) were generally bioaccumulated in both species. Among biochemical tools, GST and CAT were the most sensitive revealing the enhancement of anti-oxidant defenses in both species exposed to sub-lethal concentrations of metal-based NPs. Apoptosis and genotoxicity were frequently observed.

Heavy metal pollution status in surface sediments of Swan Lake lagoon and Rongcheng Bay in the northern Yellow Sea.

The national 'Shandong Peninsula Blue Economic Zone Development Plan' compels the further understanding of the distribution and potential risk of metals pollution in the east coast of China, where the rapid economic and urban development have been taken off and metal pollution has become a noticeable problem. Surface sediments collected from the largest swan habitat in Asia, the Swan Lake lagoon and the surrounding coastal area in Rongcheng Bay in northern Yellow Sea, were analyzed for the total metal concentrations and chemical phase partitioning of five heavy metals (Cu, Zn, Pb, Cd, and Cr). Metal contents in the studied region have increased significantly in the past decade. The speciation analyzed by the sequential extraction showed that Zn and Cr were present dominantly in the residual fraction and thus of low bioavailability, while Cd, Pb and Cu were found mostly in the non-residual fraction thus of high potential availability, indicating significant anthropogenic sources. Among the five metals, Cd is the most outstanding pollutant and presents high risk, and half of the surface sediments in the studied region had a 21% probability of toxicity based on the mean Effect Range-Median Quotient. At some stations with comparable total metal contents, remarkably different non-residual fraction portions were determined, pointing out that site-specific risk assessment integrating speciation is crucial for better management practices of coastal sediments.

Biochemical and behavioural responses of the endobenthic bivalve Scrobicularia plana to silver nanoparticles in seawater and microalgal food.

Because of their bactericidal effects, Ag nanoparticles (Ag NPs) have promising industrial development but could lead to potential ecological risks. The aim of this study was to examine the uptake and effect of silver (soluble or as lactate Ag NPs of 40 nm) at low concentrations (10 µg L(-1)) in the endobenthic bivalve Scrobicularia plana exposed, for 14 days, directly (water) or via the diet (microalgae). The stability of Ag NPs in seawater was examined using dynamic light scattering. Release of soluble Ag from Ag NPs in the experimental media was quantified by using diffusive gradient in thin film. Bioaccumulation of Ag in bivalves was measured by electrothermal atomic absorption spectrometry. Behavioural and biochemical biomarkers were determined in bivalves. Aggregation of Ag NPs and the release of soluble Ag from Ag NPs were observed in the experimental media. For both forms of Ag, bioaccumulation was much more important for waterborne than for dietary exposure. The response of oxidative stress biomarkers (catalase, glutathion S-transferase, superoxide dismutase) was more important after dietary than waterborne exposure to Ag (soluble and NPs). These defences were relatively efficient since they led to a lack of response of damage biomarkers. Burrowing was not affected for bivalves exposed directly or through the diet to both Ag forms but feeding behaviour was impaired after 10 days of dietary exposure. Since no differences of responses to Ag either soluble or nanoparticulate were observed, it seems that labile Ag released from Ag NPs was mainly responsible for toxicity.

Size dependent bioaccumulation and ecotoxicity of gold nanoparticles in an endobenthic invertebrate: the Tellinid clam Scrobicularia plana.

Gold nanoparticles (AuNPs) have important technological applications resulting in an increased potential for release to the environment, and a greater possibility of toxicological effects. The marine bivalve Scrobicularia plana was exposed to AuNPs of size 5, 15 and 40 nm during a 16 d laboratory exposure at 100 µg Au L(-1). After exposure to AuNPs forming aggregates (>700 nm), the clams accumulated Au in their soft tissues. Biochemical (biomarkers) and behavioral (burrowing and feeding) responses were investigated. Au NPs were responsible of metallothionein induction (5, 40 nm), increased activities of catalase (15, 40 nm) and superoxide dismutase (40 nm) and of glutathione S-transferase by the three sizes of AuNPs indicating defense against oxidative stress. Exposure to AuNPs impaired burrowing behavior. However, it must be underlined that these effects were observed at a dose much higher than expected in the environment.

Behavioural and biochemical responses of two marine invertebrates Scrobicularia plana and Hediste diversicolor to copper oxide nanoparticles.

Engineered nano-sized Cu oxide particles are extensively used in diverse applications. Because aquatic environments are the ultimate "sink" for all contaminants, it is expected that nanoparticles (NP) will follow the same fate. In this study, two marine invertebrates Scrobicularia plana and Hediste diversicolor were chosen as ecotoxicological models. The aim was to evaluate behavioural (burrowing kinetics, feeding rate) and biochemical (biomarkers) responses of S. plana and H. diversicolor exposed in the laboratory to Cu (10 µg L(-1)) added in natural seawater either in the form of engineered nanoparticles (NPs) of CuO or as dissolved Cu in 2% HNO(3). Exposure was characterized by considering (i) the physico-chemical fate of NP (ii) the fraction of labile Cu in experimental media and (iii) Cu bioaccumulation. Results showed high aggregation of CuO NPs in seawater and no additional bioavailable Cu concentrations. Behavioural impairments were observed in S. plana exposed to CuO NPs or soluble Cu whereas in H. diversicolor, only the exposure to soluble Cu led to a burrowing decrease. No obvious neurotoxicity effects were revealed since in both species, no changes in cholinesterasic activity occurred in response to both forms of Cu exposure. Biomarkers of oxidative-stress catalase and glutathione-S-transferase were enhanced in both species whereas superoxide dismutase was increased only in S. plana exposed to CuO NPs. Metallothionein-like protein was increased in bivalves exposed to both forms of Cu. Since, no detectable release of soluble Cu from CuO NPs occurred during the time of experiment, ecotoxicity effects seem to be related to CuO NPs themselves.

Influences of dissolved and colloidal organic carbon on the uptake of Ag, Cd, and Cr by the marine mussel Perna viridis.

The cross-flow ultrafiltration and radiotracer techniques were used to study the influences of natural dissolved organic carbon (DOC) and colloidal organic carbon (COC) on the bioavailability of Ag, Cd, and Cr to the green mussel Perna viridis. We examined the uptake of these metals by the mussels at different concentrations of DOC and COC from different origins (estuarine, coastal, and diatom decomposed). Using the DOC originating from the decomposed diatom (Thalassiosira pseudonana), we demonstrated that Cd and Cr uptake, quantified by the concentration factor (DCF), increased linearly with increasing DOC concentration. There was, however, no consistent influence of natural DOC concentration on the metal uptake when the DOC was obtained from different sources of seawater (coastal and estuarine). The influences of COC on metal bioavailability were metal-specific and dependent on the geochemical properties of colloids and colloid-metal complexation. Cd uptake rate was not influenced by the COC concentrations. Uptake of diatom-decomposed colloidal Cr was enhanced by 3.4x, whereas the uptake of diatom-decomposed colloidal Ag was decreased by 8.2x compared with the uptake of low molecular weight Cr and Ag (<1 kDa). The uptake of diatom-decomposed colloidal Cr and Ag was generally lower than the uptake of metals bound with the same type of colloids for 2 days. Further aging of the colloid-metal binding reduced metal bioavailability to the mussels. In the presence of different sizes of colloidal particles where there was no major binding of colloids with the metals, metal uptake by the mussels was not influenced by different COC concentrations. Overall, our study suggests that although metal dissociation from colloids may be an important step for the uptake of colloidal metals, other mechanisms such as pinocytosis and co-transport may also be involved in the uptake of these metals, especially in aquatic environments with high DOC and COC concentrations.