Organisms In Food Chain Research Articles

Potential thyroid hormone disorder risks of tire antioxidants to aquatic food chain organisms after absorbing free radicals in marine and freshwater environments

Tire antioxidants are essential functional chemical additives in tire rubber production. Because of the characteristic easy precipitation in the water environment, the environmental pollution problem caused by tire antioxidants is concerning. To reveal the mechanism by which tire antioxidants reduce common oxidative factors (free radicals) in the environment and to control the potential biological thyroid hormone disorder risk of tire antioxidant derivatives, eight commonly used antioxidants in tire production were selected for analysis. Firstly, the ability of tire antioxidants to reduce three different free radicals was quantitatively characterized based on Gaussian calculation method and inferring the radical reduction mechanism of tire antioxidants. Moreover, using the PaDEL-Descriptor software and random forest algorithm found that the N-octanol/water partition coefficient, a structure descriptor of tire antioxidant molecules, significantly correlated with their reducing ability. Second, molecular docking and molecular dynamics methods were used to assess the thyroid hormone disorder risk to aquatic organisms of eight antioxidants after reducing three free radicals. And this is the first study to construct an assessment score list of potential thyroid hormone disorder risk of the derivatives of tire antioxidants after reducing free radicals to marine and freshwater aquatic organisms based on the risk entropy method. Through the screening of this list, it was found that the derivative of the antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline oxidized by free radicals had the highest risk of thyroid hormone disorder. In addition, the top organism in the aquatic food chain was the most affected. This study also revealed that van der Waals interactions and hydrogen bonding were the main influencing factors of thyroid hormone disorder risk to aquatic organisms of the derivatives of tire antioxidants that reduce free radicals based on amino acid residue analysis. Overall, the results provide theoretical support for the selection of antioxidants and the avoidance and control of environmental risks in the tire rubber production process.

Structure and function of ABC transporters in oceanic species.

The pollution of the world's oceans is a mounting problem that threatens the safety and well-being of our planet. Many marine organisms and ecosystems are exposed to pollutants with currently unknown toxicity and consequences. Membrane proteins that act as xenobiotic - foreign molecule - exporters are an important line of defense against pollutants in the organisms’ environment. One of the most ubiquitous membrane transporter proteins are the ATP binding cassette transporters (ABC). Found in organisms across all domains of life and in many tissue types, ABC transporters selectively export many different small molecules from within the cell, preventing the toxic accumulation of xenobiotics within the organism. Many of the small molecules exported by ABC transporters are pollutants. However, some small molecule pollutants may act as inhibitors of ABC transporters by interacting with their binding site and impeding transport. For example, a study conducted on one transporter - ABCB1 or P-glycoprotein - in mice found that transport activity was significantly reduced in the presence of DDD, DDE, and DDT. In the case of ABC transporters in oceanic species, many reagents found polluting the ocean may inhibit ABC transporters’ ability to export their wide range of substrates. This would lead to detrimental effects to the health of organisms in the oceanic food chain (e.g. yellowfin tuna) and to embryonic development (e.g. purple sea urchin). A thorough molecular and structural investigation of these transporters expressed in marine species is necessary to determine which chemicals inhibit transport. Using cryo-EM and x-ray crystallography, we intend to study the structure of the ABC transporter active site and the differences between activating and inhibiting molecular transport.

BIODIVERSITY OF AQUATIC PLANTS AND MICROFLORA IN TAGWAI DAM, NIGERIA

Aquatic biodiversity of microflora and plants are the varieties of organisms and the ecosystems that make up the wetlands of the world and their interactions. Tagwai Dam is located in Chanchaga local government area of Niger State, Nigeria, located between longitude 60°39' to 60°44' East and latitude 34° to 90°37' North to South-west of Minna, Niger State, Nigeria. Transect sampling collection of aquatic flora and phytosociological method was adopted by using planktonic net, sterilized poly pots and plastic bottles from five sampling stations. Isolation and identification of microflora was conducted using serial dilution for bacterial species and biochemical tests for the identification. Agar pour plate method for the isolation and morphological characteristics for the identification of fungal species. The dominant families of aquatic plants included Araceae, Nymphaeaeceae, Alismataceae, Marsileaceae and Ceratophyllaceae. The identified bacterial species were Salmonella species, Proteus species, Psuedomonas species, Enterobacter species, while, the fungal species identified were Aspergillus species, Mucor pusillus, Penicillum notatum and Candida albicans were the most dominant microflora found from the sampling stations. The abundance and identification of these aquatic plants and microflora revealed there biodiversity and importance as they serve source of food and energy to the wetland. Aquatic plants and micro flora make up the ecosystem more reliable and comfortable for the aquatic animals and zooplanktons. They are the primary source of energy, the first organisms in food chain in a wetland community.

Polystyrene microplastic particles in combination with pesticides and antiviral drugs: Toxicity and genotoxicity in Ceriodaphnia dubia

Freshwater ecosystems are recognized as non-negligible sources of plastic contamination for the marine environment that is the final acceptor of 53 thousand tons of plastic per year.In this context, microplastic particles are well known to directly pose a great threat to freshwater organisms, they also indirectly affect the aquatic ecosystem by adsorbing and acting as a vector for the transport of other pollutants (“Trojan horse effect”). Polystyrene is one of the most widely produced plastics on a global scale, and it is among the most abundant microplastic particles found in freshwaters. Nevertheless, to date few studies have focused on the eco-genotoxic effects on freshwater organisms caused by polystyrene microplastic particles (PS-MPs) in combination with other pollutants such as pharmaceuticals and pesticides.The aim of this study is to investigate chronic and sub-chronic effects of the microplastic polystyrene beads (PS-MP, 1.0 μm) both as individual xenobiotic and in combination (binary/ternary mixtures) with the acicloguanosine antiviral drug acyclovir (AC), and the neonicotinoid broad-spectrum insecticide imidacloprid (IMD) in one of the most sensitive non-target organisms of the freshwater food chain: the cladoceran crustacean Ceriodaphnia dubia. Considering that the individually selected xenobiotics have different modes of action and/or different biological sites, the Bliss independence was used as reference model for this research. Basically, when C. dubia neonates were exposed for 24 h to the mixtures during Comet assay, mostly an antagonistic genotoxic effect was observed. When neonates were exposed to the mixtures for 7 days, mostly an additive chronic toxic effect occurred at concentrations very close or even overlapping to the environmental ones ranging from units to tens of ng/L for PS-MPs, from tenths/hundredths to units of μg/L for AC and from units to hundreds of μg/L for IMD, revealing great environmental concern.

Linking ecosystem services to a coastal bay ecosystem health assessment: A comparative case study between Jiaozhou Bay and Daya Bay, China

Coastal bays, situated within Earth’s critical zone, play important ecological and socioeconomic roles. This study developed an integrated ecosystem health assessment framework based on ecosystem services specific to coastal bays, particularly exploring approaches to determine critical indicators and establish a reference benchmark. The framework was applied to two typical coastal bays (Jiaozhou Bay and Daya Bay) to ascertain significant health differences, subsequent challenges and prospective management. Comparatively, Daya Bay was healthier. Daya Bay received an overall comprehensive index ecosystem health score of 69.42 (good); however, its ecosystem services scores differed significantly (supporting services = 71.34, regulating services = 87.29, provisioning services = 3.59, cultural services = 74.30), indicating severe degradation in its ecosystem food provisioning function. Jiaozhou Bay received corresponding score of 55.79 (moderate), and its ecosystem services scores were relatively lower (supporting services = 63.31, regulating service = 54.30, provisioning services = 6.18, and cultural services = 54.74), indicating widespread ecosystem degradation. The health status of coastal bays is closely associated with both natural characteristics and human interventions. The narrow bay mouth of Jiaozhou Bay, its limited enclosed seawater area, and the intensive land reclamation that has taken place since the 1950s have directly or indirectly led to the low score of most of its indicators, particularly regarding the significant reductions in its water area and shoreline. The geological advantages of Daya Bay is its large area of water and that it is open to the outer sea, which have contributed to its comparatively healthier status, wherein scores of only a few indicators were bad (i.e., biological indicators of sensitive organisms in the upper food chain). Results from this study provide important information for prospective bay management. For Jiaozhou Bay, more effort should be paid to improving ecosystem health in a comprehensive way, particularly fishing control, land reclamation control and habitat restoration. For Daya Bay, overfishing should be better controlled, while more emphasis should be paid to protecting and restoring certain moderately specific habitats and species. For effective management, we highlight that ecosystem management strategies needs to be differentiated among different bays based on their significant natural and social features. Our approach provides a practical ecosystem health assessment tool that can be applied to other coastal bays to better inform sustainable management and conservation initiatives.

δ15N of Chironomidae: An index of nitrogen sources and processing within watersheds for national aquatic monitoring programs

Nitrogen (N) removal along flowpaths to aquatic ecosystems is an important regulating ecosystem service that can help reduce N pollution in the nation's waterways, but can be challenging to measure at large spatial scales. Measurements that integrate N processing within watersheds would be particularly useful for assessing the magnitude of this vital service. Because most N removal processes cause isotopic fractionation, δ15N from basal food-chain organisms in aquatic ecosystems can provide information on both N sources and the degree of watershed N processing. As part of EPA's National Aquatic Resource Surveys (NARS), we measured δ15N of Chironomidae collected from over 2000 lakes, rivers and streams across the continental USA. Using information on N inputs to watersheds and summer total N concentrations ([TN]) in the water column, we assessed where elevated chironomid δ15N would indicate N removal rather than possible enriched sources of N. Chironomid δ15N values ranged from −4 to +20‰, and were higher in rivers and streams than in lakes, indicating that N in rivers and streams underwent more processing and cycling that preferentially removes 14N than N in lakes. Chironomid δ15N increased with watershed size, N inputs, and water chemical components, and decreased as precipitation increased. In rivers and streams with high watershed N inputs, we found lower [TN] in streams with higher chironomid δ15N values, suggesting high rates of gaseous N loss such as denitrification. At low watershed N inputs, the pattern reversed; streams with elevated chironomid δ15N had higher [TN] than streams with lower chironomid δ15N, possibly indicating unknown sources elevated in δ15N such as legacy N, or waste from animals or humans. Chironomid δ15N values can be a valuable tool to assess integrated watershed-level N sources, input rates, and processing for water quality monitoring and assessment at large scales.

Mesopelagic Fish Protein Hydrolysates and Extracts: A Source of Novel Anti-Hypertensive and Anti-Diabetic Peptides

The abundance of fish and zooplankton (1 × 109 tons to 7 × 1010 tons) in the mesopelagic zone of the ocean is a source of novel raw materials that provides opportunities for sustainable new product development. The peculiar conditions of light and pressure in this ecological zone and the position of the specific organisms in the marine food chain results in diversity in their bio-composition. Mesopelagic fish are an underutilized resource, rich in proteins and omega-3 oils, and present opportunities to develop novel feed, food and functional food ingredients and products. However, there is also a need to ensure that this resource is not overfished and is processed to optimize the catch in line with sustainability goals. There is therefore a need to establish sustainable bioprocessing technologies to yield value added products from mesopelagic fish species. In the present study, various protein extracts from the mesopelagic fish Maurolicus muelleri (M) and Meganyctiphanes norvegica (Northern Krill) (K) and combinations of proteins from these species (C) were generated using hydrolysis methods. Protein Hydrolysates were generated using four different enzymes including Alcalase, endocut-01, endogenous M/K enzymes and FoodPro PNL. Hydrolysates were characterized and assessed for their ability to inhibit enzymes important in diseases associated with metabolic syndrome. The ability of generated Hydrolysates to inhibit enzymes including Angiotensin-1-converting enzyme (ACE-1; EC. 3.4.15.1) associated with blood pressure regulation, Acetylcholinesterase (AChE; EC 3.1.1.7) associated with maintenance of the nervous system, and Dipeptidyl peptidase IV (DPP-IV; EC 3.4.14.5) linked with development of type-2-diabetes, was determined. In a separate process, the same mesopelagic fish species were transformed into fishmeal, Hydrolysates, fish-silage, and aqueous extracts (AQ) and screened for bioactivities using the same bioassays. The Hydrolysates contained greater than 60% protein (dry weight basis) when analyzed using the DUMAS method. A hydrolysate from M. muelleri generated using FoodPro PNL (M1) inhibited the ACE-1 enzyme by 89.56% when assayed at a concentration of 1 mg/ml compared to the positive control Captopril©. Aqueous extract two (AQ2) inhibited ACE-1 by 95.28% when assayed at 1 mg/ml compared to the control. Sample M1 inhibited DPP-IV by 100% and aqueous extract one (AQ1) inhibited the same enzyme by 90.08% when assayed at a concentration of 1 mg/ml compared to Sitagliptin used as the positive control. All samples assayed did not significantly inhibit the enzyme AChE–fraction C3 (combined hydrolzate 3: Krill and M. muelleri) inhibited AChE by 27.48% only. Based on these results samples M1, C3, and AQ1 were selected for further characterization and the IC50 values for each were determined in relation to ACE-1 and DPP-IV inhibition as well as their amino acid composition. Glutamate and aspartate were the most abundant amino acids in the selected samples. IC50 values of <0.2 mg/ml and distinct terminal amino acids were identified in each of the three fractions. The study shows that targeting processing of mesopelagic fish have potential to generate Hydrolysates for use in the prevention of type-2-diabetes and hypertension.

Investigation of nanoplastic cytotoxicity using SH-SY5Y human neuroblastoma cells and polystyrene nanoparticles

Nanoplastics have spread widely throughout not only the oceans but also the atmosphere, and recently created great concern about human health relevant to ingestion and accumulation of the nanoparticles by aquatic organisms in the human food-chain. However, how the nanoplastics have an affect on actual human body remains largely unknown, and in particular, little knowledge about nanoplastic exposure to the nervous system in human has been obtained in vitro and still less vivo. Here, we evaluated how much concentration of nanoplastics had a direct impact on cells in the nervous system as the fundamental information. Specifically, the cytotoxicity was investigated by exposure of polystyrene nanoparticles (PS) to cultured neural cells, human neuroblastoma cells, SH-SY5Y. Our results demonstrated that the PS exposure induced the cytotoxicity in the cells promoted differentiation into neuronal phenotype, and the adverse effect was comparable to or exceed that of acrylamide, a well-recognized potent neurotoxin. Also, the cells under PS exposure exhibited shrinkage of neurite outgrowth, morphology alteration and swelling of the nuclei, and spilling of intracellular components. Moreover, our findings indicate that the concentration of nanoplastics caused the cytotoxicity on neuronal cells is likely to be much higher than those predicted from the marine environment.

Investigation of nanoplastic cytotoxicity using SH-SY5Y human neuroblastoma cells and polystyrene nanoparticles

Nanoplastics have spread widely throughout not only the oceans but also the atmosphere, and recently created great concern about human health relevant to ingestion and accumulation of the nanoparticles by aquatic organisms in the human food-chain. However, how the nanoplastics have an affect on actual human body remains largely unknown, and in particular, little knowledge about nanoplastic exposure to the nervous system in human has been obtained in vitro and still less vivo. Here, we evaluated how much concentration of nanoplastics had a direct impact on cells in the nervous system as the fundamental information. Specifically, the cytotoxicity was investigated by exposure of polystyrene nanoparticles (PS) to cultured neural cells, human neuroblastoma cells, SH-SY5Y. Our results demonstrated that the PS exposure induced the cytotoxicity in the cells promoted differentiation into neuronal phenotype, and the adverse effect was comparable to or exceed that of acrylamide, a well-recognized potent neurotoxin. Also, the cells under PS exposure exhibited shrinkage of neurite outgrowth, morphology alteration and swelling of the nuclei, and spilling of intracellular components. Moreover, our findings indicate that the concentration of nanoplastics caused the cytotoxicity on neuronal cells is likely to be much higher than those predicted from the marine environment.

Response of bacterial communities to variation in water quality and physicochemical conditions in a river-reservoir system

The construction of high dams results in changes to the ecohydrology processes of river reaches both upstream and downstream of the dam, in addition to causing stratification of reservoir waters. Changes in these hydrodynamic processes then lead to changes in the habitats and nutrients of the waters that are important for basal food chain organisms, consequently affecting bacterial diversity. Here, the Xiangjiaba Hydropower Station (XJB) was used to investigate the above influences on microbial communities. Here, bacterial community structures were examined in 15 samples from upstream of the XJB (UD section) and 15 samples downstream of the XJB (DD section) using 16S rRNA gene sequencing. The bacterial community structures significantly differed between the surface water and 70 m of bottom water. Cyanobacteria was the dominant phylum in these communities and exhibited significantly higher abundances in the surface water. VPA (variance partitioning analysis) suggested that bacterial communities were influenced by and structured due to the combined effects of nutrient, hydrological, and environmental factors in addition to reservoir mixing dynamics. The abundance of Armatimonas, Roseomonas, Limonhabitans, and Flavobacterium were positively correlated with pH, flow velocity, and dissolved oxygen (DO). Total phosphorus (TP) was negatively correlated with the abundance of Acinetobacter, Roseomonas, Armatimonas. Burkholderia, Gemmatimonas, Nitrospira, hgcl.clade, and marine. group, all of which were highly sensitive to changes in water temperature. The results of this study can be used to understand the responses of bacterial communities to physicochemical conditions and water quality changes associated with reservoirs in order to provide a scientific basis for the protection of aquatic ecosystem stability.

Circulation of oxytetracycline- and ciprofloxacin-resistant commensal Escherichia coli strains in broiler chickens and farm environments, Bangladesh

Background and Aim:The emergence of antimicrobial resistance (AMR) in commensal organism, such as Escherichia coli of food animals, is an alarming issue for global health. It increases the possibility of transmitting AMR determinant(s) to human bacterial pathogens by transferable genetic materials, particularly by plasmids. Hence, it is important to know which resistant genes are being carried by commensal organisms in food chain in a country and their level of temporal loads. As a result, pre-emptive measures can be advocated with an aim to reduce their risks in their primary source of circulation which consequently would benefit the public health.Materials and Methods:Commensal E. coli strains from broiler chickens on randomly selected 30 farms and the farm environments were examined for the frequencies of isolation of resistant strains to oxytetracycline and ciprofloxacin. Five birds were randomly selected from each farm to collect cloacal swab samples (total of 150 samples). Furthermore, a total of 150 environmental samples comprising one each from feed, water, soil, litter, and litter damping site of each farm were screened for the isolation of commensal E. coli strains. Strains thus obtained were initially tested for their resistance to oxytetracycline and ciprofloxacin by Kirby–Bauer disk diffusion method. Oxytetracycline-resistant strains were further screened for the presence of resistance determining genes, namely, tetA, tetB, and tetC by uniplex polymerase chain reactions. Risks associated with the isolation frequency of oxytetracycline- and ciprofloxacin-resistant E. coli were also assessed by univariable logistic regression analysis.Results:The results revealed that all E. coli isolates, regardless of the source of origin, were resistant to oxytetracycline, while 78.4% (95% confidence interval [CI] 69.1-85.5%) showed resistance to ciprofloxacin. All the randomly selected (20) oxytetracycline-resistant strains harbored the tetA gene, whereas tetB and tetC were reported in three and two isolates, respectively. After univariable analysis, only one variable, that is, strain 1 of broiler chickens compared to two other strains was found to be positively associated with the isolation of ciprofloxacin-resistant E. coli (odds ratio 12.75 [95% CI 1.0-157.1], p=0.047).Conclusion:Resistance emerged against oxytetracycline and ciprofloxacin in commensal E. coli strains circulating in live poultry and farm environments in Bangladesh seems to be very high. Thus, human infection with drug-resistant E. coli strains through food chain will critically compromise the therapeutic measures currently available.

Diversity of microphytes from some reservoirs of Kolhapur district

Aquatic microphytes are pioneer organisms of an aquatic food chain. The productivity of an aquatic environment depends on the density of microphytes. These produce the food material on which other organisms in the ecosystem sustain. In this context, the present investigation was undertaken to study the diversity of microphytes from some reservoirs (Belawale Budruk, Benikare, Karanjivane, Sonali and Murgud) of Kolhapur District, Maharashtra. About 108 species of microphytes were identified from these lakes. Maximum diversity is observed from Chlorophyceae, followed by Bacillariophyceae and Cyanophyceae.

Elemental stoichiometry and compositions of weevil larvae and two acorn hosts under natural phosphorus variation

To understand how different trophic organisms in a parasite food chain adapt to the differences in soil nutrient conditions, we investigated stoichiometric variation and homeostasis of multiple elements in two acorn trees, Quercus variabilis and Quercus acutissima, and their parasite weevil larvae (Curculio davidi Fairmaire) at phosphorus (P)-deficient and P-rich sites in subtropical China where P-rich ores are scattered among dominant P-deficient soils. Results showed that elemental stoichiometry and compositions of both acorns and weevil larvae differed significantly between P-deficient and P-rich sites (p < 0.05), with the largest contribution of acorn and weevil larva P in distinguishing the stoichiometric compositions between the two site types. The two acorn species were statistically separated by their acorn elemental stoichiometry and compositions (p < 0.05), but no difference was observed on weevil larvae between the two acorn species. P was one of the few elements that were non strict homeostasis in both acorns and weevil larvae. These findings highlight the importance of both environmental influence in elemental stoichiometry and composition and physiological regulations of nutritional needs in organisms and provide possible stoichiometric responses of both plants and animals to P loading, a worldwide issue from excess release of P into the environment.

Contamination of Cu, Zn, Fe and Mn in &lt;i&gt;Katsuwonus pelamis&lt;/i&gt; (Linnaeus, 1758) from Karachi Fish Harbor and Potential Risks to Human Health

In the present study, skipjack tuna ( Katsuwonus pelamis ) from the Karachi coast between 2006 and 2011 were chosen and analyzed for the Fe, Mn, Cu and Zn levels in the edible dorsal tissues, livers, kidney, gills and gonads. The liver tissues had the highest concentrations of metals (623±103 mg kg-1 for Fe, 49±13 mg kg-1 for Mn, 67±17 mg kg-1 for Cu and 68±21 mg kg-1 for Zn). The muscle maximum concentrations of Fe, Mn, Cu, and Zn were 46±17, 6±2, 7±2 and 7±2 mg kg-1, respectively. The results revealed that Fe concentrations were higher than those of other metals. The values obtained were compared with the international regulation maximal allowable standards in seafood. The current work attested that calculated diurnal and hebdomadal intakes of Fe, Mn, Cu and Zn levels by way of consumption of skipjack tuna were not in excess of the Permissible Tolerable Daily Intake (PTDI) and Provisional Tolerable Weekly Intake (PTWI) values established by FAO/WHO. In conclusion, K. pelamis appears to be useful bioindicator due to their accumulation of the metals and continued sampling and pollution effects on food chain organisms comparatively are required for further investigations.

Assessment of agglomeration, co-sedimentation and trophic transfer of titanium dioxide nanoparticles in a laboratory-scale predator-prey model system

Nano titanium dioxide (nTiO2) is the most abundantly released engineered nanomaterial (ENM) in aquatic environments. Therefore, it is prudent to assess its fate and its effects on lower trophic-level organisms in the aquatic food chain. A predator-and-prey-based laboratory microcosm was established using Paramecium caudatum and Escherichia coli to evaluate the effects of nTiO2. The surface interaction of nTiO2 with E. coli significantly increased after the addition of Paramecium into the microcosm. This interaction favoured the hetero-agglomeration and co-sedimentation of nTiO2. The extent of nTiO2 agglomeration under experimental conditions was as follows: combined E. coli and Paramecium > Paramecium only > E. coli only > without E. coli or Paramecium. An increase in nTiO2 internalisation in Paramecium cells was also observed in the presence or absence of E. coli cells. These interactions and nTiO2 internalisation in Paramecium cells induced statistically significant (p < 0.05) effects on growth and the bacterial ingestion rate at 24 h. These findings provide new insights into the fate of nTiO2 in the presence of bacterial-ciliate interactions in the aquatic environment.

The role of microorganisms in a planktonic food web of a floodplain lake.

Food webs include complex ecological interactions that define the flow of matter and energy, and are fundamental in understanding the functioning of an ecosystem. Temporal variations in the densities of communities belonging to the planktonic food web (i.e., microbial: bacteria, flagellate, and ciliate; and grazing: zooplankton and phytoplankton) were investigated, aiming to clarify the interactions between these organisms and the dynamics of the planktonic food web in a floodplain lake. We hypothesized that hydrological pulse determines the path of matter and energy flow through the planktonic food web of this floodplain lake. Data were collected monthly from March 2007 to February 2008 at three different sites in Guaraná Lake (Mato Grosso do Sul State, Brazil). The path analysis provided evidence that the dynamics of the planktonic food web was strongly influenced by the hydrological pulse. The high-water period favored interactions among the organisms of the microbial loop, rather than their relationships with zooplankton and phytoplankton. Therefore, in this period, the strong interaction among the organisms of the grazing food chain suggests that the microbial loop functions as a sink of matter and energy. In turn, in the low-water period, higher primary productivity appeared to favor different interactions between the components of the grazing food chain and microorganisms, which would function as a link to the higher trophic levels.

Effects of sample preparation on methylmercury concentrations in Arctic organisms

The biogeochemical cycling of mercury (Hg) in the marine environment is an issue of global concern, as consumption of marine fish is a major route of human exposure to the toxic specie methylmercury (MeHg). The most widely utilised and accepted technique for preparing biological tissue samples for the analysis of MeHg involves an alkaline digestion of the sample. Recent studies suggest, however, that this technique is inadequate to produce satisfactory recoveries for certain biological samples, including fish, fur, feathers and other ‘indicator’ tissues which contain relatively high levels of MeHg. Thus an improved acidic extraction method has been proven to produce more satisfactory results for a wide range of biological tissues. The present study compares the two methods on real sample material from different organisms of an Arctic marine food chain, and shows how this could lead to misinterpretation of analytical results. Results show significantly (p < 0.05) lower concentrations for alkaline digestion for large parts of the food chain; especially in fish and birds. The mean differences in concentrations found between the two different methods were 28, 31 and 25% for fish (Polar and Atlantic cod), Little Auk and Kittiwake, respectively. For samples lower in the food chain (i.e. zooplankton and krill) no significant differences were found. This leads to a clear underestimation of the levels of MeHg found higher up in these food chains; the ratio of MeHg to Hg in biological samples; and thus potentially erroneous conclusions drawn from these results concerning the biological cycling of mercury species. We hypothesise that the main reasons for these differences are poor extraction efficiency and/or matrix effects on the ethylation step prior to analysis. This is the first study to examine the effects of these artefacts on real environmental samples covering a complete food chain.

Current Biotechnological Advancements on Sustainable Metal and Nutrient Removal

Current Biotechnological Advancements on Sustainable Metal and Nutrient Removal

Bioaccumulation of silver nanoparticles into Daphnia magna from a freshwater algal diet and the impact of phosphate availability

This study assessed the bioavailability, toxicity, and transfer of silver nanoparticles (AgNPs) in comparison with AgNO3 in two model food chain organisms: the alga Chlamydomonas reinhardtii and the grazing crustacean Daphnia magna. The effects of phosphate, a potential Ag+-binding ligand and a determinant of phytoplankton productivity, were evaluated. Nano Ag derived from coated AgNPs and AgNO3 was accumulated at similar concentrations into microalgae during high phosphate treatment, but AgNO3 accumulation was increased by low phosphate availability. After feeding on Ag-containing algae, D. magna equally accumulated AgNO3 and nano-derived Ag. There were significant reductions in feeding when D. magna were fed Ag-contaminated algae, with the AgNO3, low phosphate-exposed cells being ingested the least. Nutritional quality characteristics including fatty acid and trace nutrient content were similar in all algal samples, indicating that feeding reduction is specifically due to the presence of Ag, with AgNO3 being more toxic than nano Ag.

Arsenic toxicity in crop plants: physiological effects and tolerance mechanisms

Heavy metals are toxic substances released into the environment, contributing to a variety of toxic effects on living organisms in food chain by accumulation and biomagnifications. Certain pollutants such as arsenic (As) remain in the environment for an extensive period. They eventually accumulate to levels that could harm physiochemical properties of soils and lead to loss of soil fertility and crop yield. Arsenic, when not detoxified, may trigger a sequence of reactions leading to growth inhibition, disruption of photosynthetic and respiratory systems, and stimulation of secondary metabolism. Plants respond to As toxicity by a variety of mechanisms including hyperaccumulation, antioxidant defense system, and phytochelation. Arbuscular mycorrhizae symbiosis occurs in almost all habitats and climates, including disturbed soils. There is growing evidence that arbuscular mycorrhizae fungi may alleviate metal/metalloid toxicity to host plant. Here, we review (1) arsenic speciation in the environment and how As is taken up by the roots and metabolised within plants, and (2) the role of arbuscular mycorrhizae in alleviating arsenic toxicity in crop plants.