Bioaccumulation Of Zn Research Articles

Single and Combined Effect of Cd and Zn on Growth, Metal Accumulation and Mineral Nutrition in Tobacco Plants (Nicotiana tabacum L.)

AbstractContamination by heavy metals (HM) is a global concern due to their impact on terrestrial and aquatic environments. This question has great relevance in agricultural areas due to excessive chemical fertilization. In this sense, Cd is a toxic element that can reach agricultural soils through chemical fertilization or sewage sludges. Tobacco plants (Nicotiana tabacum L.)can uptake and accumulate Cd in their tissues, and therefore, an increased risk for human health due to tobacco consumption. This study was performed to evaluate the response of tobacco plants to a single and combined amendment of Cd and Zn on agricultural soil with a pot experiment. A factorial experiment was performed with four Cd levels (0, 25, 50 and 100 mg kg-1) and three Zn levels (0, 15 and 25 mg kg-1). Growth, Cd and Zn bioaccumulation and nutrient uptake parameters were assessed. The results revealed that during the tobacco growth, Cd was bioaccumulated on roots (translocation factor <1), while Zn was bioaccumulated on the aerial part (TF>1). Besides, the Zn amendment significantly decreased the Cd uptake and accumulation, especially under intermediate doses (15 mg kg-1Zn). Zinc amendments could be helpful as a mitigation measure for Cd uptake in tobacco plants and, therefore, for health risk reduction.

Assessment of trace elements and fluoride originating from phosphogypsum in the sediment of Gulf of Gabes (southeastern Tunisia): what are the potential sources of accumulation and bioavailability?

To assess potential impacts of industrial activities on the pollution status of Gulf of Gabes, twenty sediment and water samples along with phytoplankton enumeration were achieved at different stations with specific features. Comparing trace element concentrations in sediment to applicable SQG standards, we were intrigued by an accumulation of Zn, Cr, Ni, and especially Cd, which exhibited relatively high content compared to these standards. Moreover, trace metal bioavailability was high in front of industrial discharge areas. The chemical speciation pointed out a high affinity of Pb, Zn, Cr, Mn, Ni, Co, and Fe for the residual fraction of the sediment. Bioavailability of trace elements was confirmed in surface sediment by the presence of a potential toxic fraction especially in front of industrial discharge areas. Toxicity assessment performed for the first time in the Gulf of Gabes through SEM and AVS models pointed to a high potential risk near both Ghannouch and Gabes Ports. Finally, the correlations between phytoplankton species and the labile fraction inferred potential phytoplankton bioaccumulation of Zn, Cu, and Cd both in the seawater and in the labile fraction.

Transfer and transformation characteristics of Zn and Cd in soil-rotation plant (Brassica napus L and Oryza sativa L) system and its influencing factors

Rice–rape rotation is a widely practiced cropping system in China. However, changes in soil properties and management could change the bioavailability of Cd, In order to explore the occurrence state, transportation and transformation characteristics of heavy metals Cd and Zn in rice-rape rotation system in Guizhou karst area with high background value of Cd. In the karst rice–rape rotation area, the physical and chemical properties of soil, chemical specifications and activities of Cd and Zn at different soil depths and during various crop growth stages, and the bioaccumulation of Cd and Zn in different tissues of rice and rape were studied by field experiment and laboratory analysis. The bioaccumulation of Cd and Zn and the effects of physical and chemical soil properties on the activities and bioavailabilities of Cd and Zn during rice–rape rotation were explored. The findings revealed that soil particle size, composition, pH, redox potential, soil organic matter, and Cd and Zn contents varied dramatically, especially in deep soils. The physical and chemical properties of the deep and surface soils were significantly related to the bioaccumulation of Cd and Zn. Cd and Zn are activated during crop rotation. Cd was easier to be enriched in rice, while Zn was easier to be enriched in rape. The correlation between Cd and Zn contents in Brassica campestris L and their enrichment abilities were not significant, but that in Oryza sativa L were significant. During rice-rape rotation, the chemical speciations and activities of Cd and Zn changed with the changes of soil properties and waterlogging environment. This study had important basic guiding significance for the evaluation, prevention and control of heavy metal pollution, and improving soil quality in different rotation systems in karst areas, and was conducive to promoting the safe production of rape and rice.

Aluminium-based galvanic anode impacts the photosynthesis of microphytobenthos and supports the bioaccumulation of metals released

Very few studies have looked at the potential biological effects of degradation products of galvanic anodes particularly on primary producers which are central to food webs in marine ecosystems. The galvanic anode cathodic protection system (GACP) is widely used to protect submerged metallic structures from corrosion. Aluminium (Al) and zinc (Zn) are the main constituents of galvanic anodes and are therefore released in the marine environment by oxidation process to form ions or oxy-hydroxides. The main objective of our study was to evaluate the effects of the metals released from an aluminium-based galvanic anode on microphytobenthos performance in term of biofilm growing through the analysis of photosynthetic parameters, the determination of chlorophyll and extracellular polymeric substances (EPS). The bioaccumulation of Al and Zn were measured in the microphytobenthic compartment collected at the surface of polyvinyl chloride (PVC) plates exposed during 13 days to seawaters enriched in different concentrations of metals released from dissolution of one anode. Determination of bioconcentration factors confirmed that the microphytobenthos has incorporated Al. A significative effect was observed on the Chl a concentration for the higher tested concentration ([Al] = 210.1 ± 60.2 µg L − 1; [Zn] = 20.2 ± 1.4 µg L − 1). The seawater exposed to the anode affected the MPB productivity (ETRIImax) with consequences on acclimatation light (Ek), absorption cross section of PSII (σPII), Fv/Fm and NPQ. Regarding the EPS production, the anode degradation presented an impact on high and low molecular weight of both carbohydrates and protein fractions of microphytobenthos suggesting that EPS play an essential role in sequestering metal contaminants to maintain the integrity of the biological membranes and the functionality of the cellular organelles. The accumulation of Al released by GACP in microphytobenthos cells could lead to physiologic problems in photosynthetic organisms.

How fish cells responded to zinc challenges: Insights from bioimaging

Zinc ion (Zn) is an essential nutrition element and it is important to understand its regulation and distribution among different cellular organelles. Here, subcellular trafficking of Zn in rabbitfish fin cells was investigated through bioimaging, and the results showed that the toxicity and bioaccumulation of Zn were both dose- and time-dependent. Cytotoxicity of Zn only occurred when the Zn concentration reached 200–250 μM after 3 h of exposure when the cellular quota of Zn:P reached a threshold level around 0.7. Remarkably, the cells were able to maintain homeostasis at a low Zn exposure concentration or within the first 4-h exposure. Zn homeostasis was mainly regulated by the lysosomes which stored Zn within the short exposure period, during which the number and size of lysosomes as well as the lysozyme activity increased in response to incoming Zn. However, with increasing Zn concentration beyond a threshold concentration (> 200 μM) and an exposure time > 3 h, homeostasis was disrupted, leading to an Zn spillover to cytoplasm and other cellular organelles. At the same time, cell viability decreased due to the Zn damage on mitochondria which caused morphological changes (smaller and rounder dots) and over production of reactive oxygen species, indicating the dysfunction of mitochondria. By further purifying the cellular organelles, cell viability was found to be consistent with the mitochondrial Zn amount. This study suggested that the amount of mitochondrial Zn was an excellent predictor of Zn toxicity on fish cells.

Potential ecotoxicity of substrate-enriched zinc oxide nanoparticles to Physalaemus cuvieri tadpoles

Although the ecotoxicological effects of ZnO nanoparticles (ZnO NPs) have already been reported in different taxa, little is known about their impacts on amphibians. Thus, we aimed to evaluate the potential effects of exposure of Physalaemus cuvieri tadpoles to substrates enriched with ZnO NPs (and with its ionic counterpart, Zn+2, ZnCl2 – both at 100 mg/kg) previously used in the cultivation of Panicum maximum (Guinea grass). We showed that although exposure for 21 days did not impact the survival, growth, and development of tadpoles, we noted an increase in the frequency of erythrocyte nuclear abnormalities in the “ZnCl2” and “ZnONP” groups, which was associated with suppression of antioxidant activity in the animals (inferred by SOD and CAT activity and DPPH free radical scavenging capacity). In the tadpoles of the “ZnONP” group, we also noticed a reduction in creatinine and bilirubin levels, alpha-amylase activity, and an increase in alkaline phosphatase activity. But the treatments did not alter the activity of the enzymes lactate dehydrogenase and gamma-glutamyl-transferase and total protein and carbohydrate levels. On the other hand, we report a cholinesterase and hypotriglyceridemic effect in the “ZnCl2” and “ZnONP” groups. Zn bioaccumulation in animals, from ZnO NPs, from Zn+2 released from them, or both, has been associated with causing these changes. Finally, principal component analysis (PCA) and the values of the “Integrated Biomarker Response” index revealed that the exposure of animals to substrates enriched with ZnO NPs caused more pronounced effects than those attributed to its ionic counterpart. Therefore, our study reinforces the need to consider the environmental risks of using these nanomaterials for agricultural purposes for amphibians.

Phytoremediation and Nurse Potential of Aloe Plants on Mine Tailings

Mine tailings are a source of potentially toxic metals (PTMs) worldwide. Phytoremediation is a low-cost green technology that uses metal-tolerant plants to extract these contaminants and rehabilitate the soil. In mine tailing restoration efforts, it can be beneficial to introduce species that can facilitate the colonization of other plants (i.e., nurse plant syndrome). In this study, the phytoremediation and nursing potential of two species adapted to metalliferous soil, Aloe burgersfortensis and A. castanea, were evaluated for the first time. An experiment was performed with aloe plants grown in pots containing potting soil, platinum tailings, and gold tailings. Leaves were assessed for bioaccumulation of PTMs. Seeds of Bermuda grass and African daisy, two successional pioneers, were planted with the aloes and had their developmental parameters evaluated after 30 days. Allelopathic effects were also assessed, with seeds of the pioneer plants infused with root extracts of the aloes from the different soil treatments. A. castanea demonstrated greater potential for the bioaccumulation of Cd, Co, Mn, Ni, and Zn in the tailings. The presence of aloes benefited germination rates, leaf count, length, and plant biomass of grasses and daisies in the mine tailings, without significant allelopathic effects. Therefore, aloes-especially A. castanea-should be employed in the rehabilitation of metal-contaminated soils to extract metals and to aid the establishment of other species to enhance the phytoremediation processes.

Field evaluation of metal bioaccumulation in the gastropod Helix aspersa at agricultural and industrial sites in Lebanon.

Juvenile Helix aspersa Müller exposed in field microcosms were used to assess the spatial and temporal bioaccumulation of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn at two agricultural and two industrial sites in Lebanon. The study was performed over a 12-week period where caged snails were sampled once every 3weeks and assessed for metal bioaccumulation and partitioning between soft tissue and shells. Results showed that metal bioaccumulation by snails was site dependent, with Fe and Cd being the greatest and least accumulated metals, respectively. Significant differences between bioaccumulation in each of the matrices (soft tissue and shells) were also observed. Time-dependent bioaccumulation results showed an increasing accumulation trend at both agricultural sites, while a slight decline was observed at the end of the sampling campaign for the industrial sites. The study of the bioaccumulation factors (BAF) revealed that tested H. aspersa were macroconcentrators for Zn and Cd (BAF > 2) and deconcentrators for all other analyzed elements (BAF < 1). The high partitioning factor values obtained for Cu and Zn indicate an affinity of these two elements for the soft tissues of the snails. The results of this field study indicate that H. aspersa are well suited for active biomonitoring and could provide reliable information on metal pollution and bioavailability.

The Role of Mycorrhizal-Assisted Phytomining in the Recovery of Raw Materials from Mine Wastes

In recent years, critical and secondary raw materials (CRMs and SRMs, respectively) have received great interest within the circular economy model. In this work, the mycorrhizal-assisted phytomining (MAP) system, composed of Helianthus annuus–arbuscular mycorrhizal fungus Rhizophagus intraradices–Zn-volcanic ashes, was applied in bioreactors for the recovery of CRMs (Sr, P) and SRMs (Cr, Zn, Cu, Mn, Rb, Ni) from mining wastes of the Los Cóndores mine (Argentina). Our results showed high bioaccumulation of Sr, P, Mn, and Zn in the aerial tissues, and a high root-to-shoot translocation for Mn (4.02) &gt; Sr &gt; P &gt; Rb &gt; Zn (0.84). Mycorrhization treatment increased the root-to-leaf translocation for Cr and P and prevented translocation towards flower tissues in most elements. The estimated bioextracting potential of the MAP system (290 plants) in a vegetable depuration module (VDM) ranged from 158 mg/m3 P &gt; Zn &gt; Mn &gt; 15.1 mg/m3 Sr. We demonstrated a promising and cost-effective biotechnology applicable in agronomical practices, given the exclusion of toxic elements in flower parts, as well as for the recovery of CRMs and SRMs by hydrometallurgy from plant biomass.

Improved efficacy of foliar application of zinc oxide nanoparticles on zinc biofortification, primary productivity and secondary metabolite production in dragonhead

Improving medicinal plants' performance in semi-arid regions facing climate change could support sustainable food and agriculture production. Nano-fertilization is considered an emerging strategy for increasing plant production, while avoiding agroecosystem contamination. The objective of this study was to evaluate potential beneficial effects of foliar applications of two sources of zinc (Zn oxide nanoparticles [ZnONPs] as a novel nano-fertilizer and Zn suspension [ZnS] as a conventional fertilizer) on Zn biofortification, primary productivity (biomass) and secondary metabolite production in a medicinally important dragonhead (Dracocephalum moldavica L.) under semi-arid conditions. After 60- and 74-day post-planting, the desired fertilizers were sprayed on to plant foliage. The results showed that leaf Zn bioaccumulation, total chlorophyll, and total flavonoids increased in a dose-dependent manner for both Zn compounds. Sub-toxic levels of Zn-based NPs uptake (up to on average 152.6 mg Zn/kg upon foliar treatment with 160 mg ZnONPs treatment) led to stimulatory effects on total chlorophyll (0.93 g/kg FW), shoot biomass (2168 kg/ha), and essential oil content (3.4 g/kg) and yield (7.4 kg/ha) compared to ZnS treatment or control. The levels of secondary metabolites including neral, geraniol and geranial increased significantly with 160 mg/L ZnONPs compared to equivalent concentration of ZnS or control. The TEM analyses of leaf ultrastructure revealed changes in cellular organelles at 400 mg/L ZnONPs, likely a result of higher oxidative stress (malondialdehyde and H2O2). Higher efficacy of ZnONPs will support greater economic return for dragonhead growers and curtail environmental pollution. Foliar application of 160 mg/L ZnONPs is recommended for optimal micronutrient Zn biofortification, biomass production and essential oil yield in dragonhead, and may serve as a sustainable strategy to promote agricultural yield in (semi-) arid regions.

Differential Physiological Response and Potential Toxicological Risk of White Cabbage Grown in Zinc-Spiked Soil

Physiological, agricultural and toxicological impact of an excess of Zn in the soil is an important issue, as Zn is a heavy metal and impairs many processes of plants and animals. The novelty of this work is that it is a comprehensive approach to facilitate visualization not only of the condition of cabbage plants under Zn stress, but also prediction of the toxicity associated with consumption of such cabbages. We treated plants of two cabbage cultivars, differing in their earliness, with 50 and 200 mg Zn kg−1 soil (Zn50 and Zn200, respectively) above the natural Zn levels of 118.13 mg kg−1 soil (Zn0). Leaf cell membrane integrity, condition of the photosynthetic apparatus (reflected by relative chlorophyll content (SPAD) and Fv/Fm parameter of chlorophyll a fluorescence), head biomass, and Zn bioaccumulation in the heads were analyzed. Toxicological risk was also assessed by Daily Intake of Metal (DIM) and Health Risk Index (HRI) indicators. The data revealed that plants of the late cultivar were more sensitive to soil Zn than those of the early one. Detrimental effects of Zn (especially at the higher dose, Zn200) were manifested in the seedlings just after three weeks of treatment, and then reflected in the yield. We assume that, due to their fast and prolonged response to Zn, the seedlings of the late cultivar can be used as biomarkers of Zn toxicity. Although Zn plants did not indicate toxicological risk, based on DIM and HRI, Zn concentration in the soil should be taken into account prior to cabbage planting, because plants which do not reveal symptoms of injury can accumulate Zn above the permissible level.

Bioaccumulation of Cu, Fe and Zn in Wild Ruminants in Middle Gemer Region

The aim of this study was to monitor trace metals (copper, iron and zinc) concentrations in parenchymatous organs and muscle tissue of red deer (n=23) and roe deer (n=25) that were hunted down in the middle Gemer region in south central Slovakia. Being expressed in mg kg–1 in all cases, these concentrations assumed the following values: mean renal copper concentration in red deer was 4.36, hepatic 19.65, muscle 1.96; renal iron concentration was 72.5, hepatic 131.9, muscle 45.09; mean zinc concentration in kidney was 27.77, in liver 30.22 and in muscle 29.58 , respectively. In roe deer, mean level of copper in kidney was 4.83, in the liver 26.4, in muscle tissue 2.1; mean concentration of iron in kidney was 66.69, in liver 122.83, in muscle tissue 49.07; mean concentration of zinc in kidney was 27.34, in liver 29.76, and in muscle tissue 24.37, respectively. Concentration of metals under study in different age groups showed that the values rose proportionally with age except for zinc concentration, where the highest Zn concentrations were detected in muscle of young animals. In other trace metal levels no significant differences were detected between age groups, males or females. Based on the given results, the Revuca district does not show itself as the most polluted region considering surveyed heavy metals, but nevertheless the presented results document that the presence of heavy metals in the tissues of game is still an interesting object for the next studies.

Insights into the kinetic regulation of Zn bioaccumulation at trace levels: Lighting up Saccharomycescerevisiae

Zn displays a double-edged effect by acting both as a micronutrient and a toxic metal, and quantitative analysis of its kinetic flux under low environmental concentrations is critical to understand its intracellular regulation. In the present study, we employed a Zn sensitive model eukaryote, the yeast Saccharomyces cerevisiae, which responded to intracellular Zn levels by increasing its autofluorescence, to quantify Zn influx, transportation between labile and storage pools, and efflux under different Zn exposure levels (<1 μM). We demonstrated that the yeast regulated Zn uptake from the extracellular source by a gradually decreased accumulation following an initial high accumulation rate. The subsequent reduced accumulation rate resulted in a steady-state Zn accumulation at 0.061 and 0.073 μg Zn/μg P as the threshold values for the control yeast and Zn-depleted yeast, respectively, independently of the extracellular Zn concentration. Compared with the control yeast, the Zn-depleted yeast possessed a higher accumulation rate, but the difference of bioaccumulation was maintained at approximately 0.01 μg Zn/μg P under different concentrations of extracellular Zn. In contrast, transportation between labile Zn and storage Zn pools or Zn efflux to the extracellular environment was not obvious after Zn exposure, indicating that the Zn dose was below a basal requirement. Such stabilized Zn accumulation was only induced by controlling the Zn influx at the bio-interface. With the novel monitoring of the kinetic changes of autofluorescence, our study demonstrated a remarkably tight Zn regulation system in yeast, providing enlightenment for Zn homeostasis in eukaryotes under low Zn exposure in aqueous environments.

In Situ Assay of Interfacial Interaction between ZnO Nanoparticles and Live Cell Disturbed by Surfactants.

The interfacial interaction between pollutants and organisms is a critical process in controlling the environmental fates of pollutants; however, in situ assay of the interaction is still a great challenge. Here, in situ determination of dissociation constants (Kd) for ZnO nanoparticles (ZnO NPs) from live algal cells disturbed by different-charged surfactants was established using microscale thermophoresis (MST). Moreover, in situ measurement of the adhesion force between the ZnO NPs probe and live single cell was performed using an atomic force microscope (AFM). Results showed that the cationic cetyltrimethylammonium chloride (CTAC) and anionic sodium dodecylbenzenesulfonate (SDBS) increased but nonionic Triton X-100 (TX-100) decreased the adhesion of ZnO NPs on cells. However, the force signature exhibited a smooth single retracted peak at short distances in the SDBS- and TX-100-treated groups, distinguished from the "see-saw" pattern peak in the CTAC-treated groups. The extended Derjaguin-Landau-Verway-Overbeek (XDLVO) calculation further confirmed that SDBS and TX-100 mainly disturbed the short-range hydration on the NP-cell interface, while CTAC reduced the long-range electrostatic repulsion. Furthermore, an excellent linear correlation between Zn bioaccumulation and two parameters (Kd and adhesion force) indicated that NP-cell interfacial interactions affected Zn bioaccumulation. Thus, in situ assay provides a quantitative basis for the pollutant-organism interfacial interaction to evaluate the environmental fate and ecological risk of pollutants.

Modelling the bioconcentration of Zn from commercial sunscreens in the marine bivalve Ruditapes philippinarum

Sunscreens contain ZnO particles used as a UV filter cause adverse effects in the marine environment through the release of this metal into seawater and its bioaccumulation in organisms. A mathematical model using sunscreen colloidal residues, seawater and R. philippinarum clams as differentiated compartments, is proposed in order to interpret both the kinetic pattern and the bioaccumulation of Zn in clams. Two kinetic laboratory experiments were conducted, both with and without clams exposed to sunscreen concentrations from 0 to 200 mg L−1. Both the lowest value of uptake rate coefficient obtained when 5 mg L−1 of sunscreen is added (0.00688 L g−1 d−1) and the highest obtained at sunscreen addition of 100 mg L−1 (0.0670 L g−1 d−1), predict a lower bioavailability of Zn in a complex medium such as the seawater-sunscreen mixtures, in comparison to those studied in the literature. The efflux rate coefficient from clams to seawater increased from 0 to 0.162 d−1 with the sunscreen concentrations. The estimated value of the inlet rate coefficient at all studied concentrations indicates that there is a negligible colloidal Zn uptake rate by clams, probably due to the great stability of the organic colloidal residue. An equilibrium shift to higher values of Zn in water is predicted due to the bioconcentration of Zn in clams. The kinetic model proposed with no constant Zn (aq) concentrations may contribute to a more realistic prediction of the bioaccumulation of Zn from sunscreens in clams.

Chronic toxicity, bioavailability and bioaccumulation of Zn, Cu and Pb in Lactuca sativa exposed to waste from an abandoned gold mine

Abandoned mines with untreated waste cause environmental pollution. The complex mixture of mining waste includes high metal content, anthropogenic chemicals and sterile rocks. Adverse effects of contaminated soils have been widely assessed by the use of plants. The aim of this study was to assess the chronic toxicity of a contaminated soil by waste from an abandoned gold mine on Lactuca sativa and its relationship with the bioavailability and bioaccumulation of Zn, Cu and Pb. Soil samples were taken from the site of mining waste stacking and a reference site in La Planta (Argentina). Contamination indices were calculated and acute and chronic exposures on L. sativa were carried out. Phytotoxicity indices, morphological and biochemical parameters, and concentrations of Zn, Cu and Pb in pseudo total and bioavailable soil fractions and in plant tissue were determined. Concentration- and time-dependent toxicity effects were observed, especially on plant width, fresh aerial biomass, leaf area and percentage of plants with completely necrotic aerial biomass. High levels of Zn (1453.3 ± 220.3 μg g−1) were found in plant tissue compared to Pb (277.2 ± 18.0 μg g−1) and Cu (255.3 ± 25.6 μg g−1). Toxicological endpoints correlated with metal uptake and mining waste concentration. In addition, bioaccumulation factors correlated with mobilisable and water soluble fractions. The concentration of Pb in aerial biomass surpassed the permissible concentrations in leaf vegetables, even at the reference site, indicating that lettuce crop consumption could be risky for the local population's health. This study demonstrated a strong relationship between metal bioavailability, toxicity endpoints and bioaccumulation, contributing with novel information to future ecotoxicological risk assessments and remediation plans.

A field study on the composition, structure, and function of endophytic bacterial community of Robinia pseudoacacia at a composite heavy metals tailing

Robinia pseudoacacia (R. pseudoacacia) is a well reported plant species for heavy metal phytoremediation, and it was capable to improve Cd uptake efficiency after inoculated with plant growth promoting endophytes. However, the knowledge on R. pseudoacacia associated endophytes in field condition and the relationship between these microbial communities and heavy metal uptake capacities are still scarce. In this study, the characteristics of heavy metal bioaccumulation and translocation in R. pseudoacacia, and the structure and function of its endophytic bacterial communities were revealed. The results showed that heavy metal pollution made microbes more sensitive to the environment as the diversity (Shannon) of endophyte community decreased but the abundance (Chao) increased. Redundancy analysis (RDA) also showed that heavy metals were the key factor affecting the composition of endophyte. In the co-occurrence network, 27 keystone taxa mainly from Actinobacteria, Proteobacteria and Firmicutes occupied the dominant niches, among which 16 OTUs mainly from lactobacillus, bacteroides, staphylococcus, methylorubrum and bifidobacterium were positively related to bioaccumulation and translocation of Cd, Cu, Pb and Zn. Besides, heavy metal stress enhanced the functional adaptability of endophytic bacteria community. Related predicted genes were enriched in immune response, physiological metabolism pathway and stress-resistant enzyme synthesis. This study showed that heavy metal stress enhanced the structural and functional adaptability of endophyte community and keystone taxa played significant role in improving the efficiency of phytoremediation.

Heavy metal accumulation in selected fish species from Pulicat Lake, India, and health risk assessment

Heavy metal pollution in aquatic systems has become a major problem worldwide. The present study was designed to assess bioaccumulation of metals, Cu, Zn, Pb, and Cr, in fish species such as Lutjanus fulviflamma, Chanos chanos, Arius sp., and Terapon jarbua, commonly present in the Pulicat Lake, a brackish water ecosystem located in north Chennai coastal region, southeast India. Mean concentration of Cu and Cr in the sediment samples were 123.1μg/g and 90.1μg/g, respectively. The order of metal prevalence in water and sediment samples were Pb>Cr>Zn>Cu and Cu>Cr>Pb>Zn, respectively. However, in fish samples, the order of metal accumulation was Cu>Cr>Zn>Pb. Mean concentration of Cu in L. fulviflamma, C. chanos, Arius sp., and T. jarbua was 10.5μg/g, 25.5μg/g, 19.0μg/g, and 23.6μg/g, respectively. Mean Cr concentration in the animals varied from 1.19μg/g to 23.1μg/g with highest accumulation in the liver of Arius sp. In general, maximum accumulation of metals is mostly observed in the gills of the organisms. Although the concentration of Cu and Cr in the muscles was above World Health Organization’s permissible limit, the Estimated Daily Intake values were below the standard reference dose which means that the muscle tissues of the fishes are safe for human consumption.

Interplay of Seasonality, Major and Trace Elements: Impacts on the Polychaete Diopatra neapolitana.

Simple SummaryCoastal systems often serve as sinks for toxic elements, and seasonality has been responsible for many changes in the physical and chemical parameters of waters and sediments, leading to geochemical alterations in aquatic systems and the alteration of element uptake rates in organisms. Diopatra neapolitana worms were collected from five sites of the Ria de Aveiro lagoon in the autumn, winter, spring, and summer of 2018/2019 and were tested to check for differences in the biochemical responses (cell damage, antioxidant enzymes, biotransformation enzymes, and energy-related parameters) among seasons and sites. In general, the results demonstrated that enzyme activities were higher in spring and summer due to high temperatures and element bioaccumulation. Energy-related parameters presented with higher levels in spring and autumn, which was mainly due to element bioaccumulation. Oxidative damage was higher during winter and was related to salinity and decreases in temperature. This study demonstrated that abiotic factors influence the geochemistry of elements and that both significantly affect organism performance in low-contamination systems, such as the Ria de Aveiro lagoon. This knowledge is important to understand how ecological and economically relevant species such as D. neapolitana respond to environmental changes.Polychaetes are known to be good bioindicators of marine pollution, such as inorganic contamination. Major and trace elements are commonly present in sediment and may be accumulated by polychaetes such as the tubiculous Diopatra neapolitana. In this study, D. neapolitana individuals were collected in the autumn, winter, spring, and summer of 2018/2019 from the Ria de Aveiro lagoon (western Portugal) to understand how seasonality influences element accumulation. The impact of the interaction of seasonality and elements on oxidative status, energy metabolism, and oxidative damage was also assessed. The obtained results showed that the activity of the antioxidant enzymes catalase, glutathione S-transferases, and non-protein thiol levels were higher in summer and that superoxide dismutase, lipid peroxidation, and electron transport system activity increased in winter. The lowest glycogen levels were observed during spring, and protein carbonylation was the highest during autumn. These results could mainly be related to high temperatures and the bioaccumulation of Al, As, Mn, and Zn. Energy-related parameters increased during spring and autumn, mainly due to the bioaccumulation of the same elements during spring and summer. Lipid damage was higher during winter, which was mainly due to salinity and temperature decreases. Overall, this study demonstrates that seasonality plays a role in element accumulation by polychaetes and that both impact the oxidative status of D. neapolitana.

Improving water quality, growth performance, and modulating some stress physiological biomarkers in Cyprinus carpio using raw date nuclei as a zinc adsorbent agent

Adsorption of heavy metals by affordable adsorbents has recently become one of the most often applied method for removing these metals from contaminated water. The purpose of this study was to evaluate the efficacy of using raw date nuclei (RDN) as a natural and inexpensive adsorbent to remove Zn ions from contaminated water and reduce its impact on water quality, Zn bioaccumulation levels in fish organs, growth performance, and some physiological aspects of common carp (Cyprinus carpio) under sublethal concentrations. Five experimental groups were examined for eight weeks; CNT, control group rearing in clean water; RDN0, fish group rearing in Zn-contaminated water; RDN3, fish group rearing in Zn-contaminated water and treated with 3 g RDN/L; RDN4.5, fish group rearing in Zn-contaminated water and treated with 4.5 g RDN/L; RDN6, fish group rearing in Zn-contaminated water and treated with 6 g RDN/L. Water quality measures were monitored in a continuously manner without removing fish excreta or renewing water. The results showed that sublethal concentration of Zn alone significantly elevated the level of antioxidant biomarkers (SOD, superoxide dismutase; GST, glutathione transferases; GPX, glutathione peroxidase; CAT, catalase and MDA, malondialdehyde), significantly declined fish performance, increased Zn-accumulation in fish organs (gills and flesh) and increased the ammonia secretions in fish ponds compared to the control group. Zn concentrations in RDN-containing aquariums were significantly lower than in RDN-free aquariums, and Zn removal from polluted water was dependent on RDN dosage. Consequently, fish performance and serum bio-indicators enhanced in the presence of RDN in a fish group reared under sublethal Zn concentrations. In conclusion, although Zn caused toxicity in C. carpio at sublethal levels, treating Zn-contaminated water with RDN at a dosage of 6 g per liter effectively prevented oxidative stress and the harmful impacts of Zn exposure.