Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Food Chain”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41Linked to original sources
PubMed2002

Trace organic compounds in the marine environment.

Trace organic chemicals include a range of compounds which, due to a combination of their physico-chemical properties and toxicological implications, have been described as a serious threat to the biotic environment. A global treaty to regulate the manufacture and release of some of the most persistent trace chemicals has been promulgated and signed. The marine environment is an important sink for many trace chemicals, some of which accumulate in the marine food chain and in particular in marine mammals. With respect to the global distribution of trace organic chemicals, the levels of organohalogen compounds in the Southern Hemisphere are comparatively lower for a given environmental compartment and latitude compared to the Northern Hemisphere. A debate is currently evolving about the toxicity of alternative halogen substitutions such as bromine instead of chlorine and also of mixed halogen substitution. Recently a series of potentially natural bioaccumulative and persistent organohalogen chemicals have been found in marine mammals and turtles at levels in excess of those of anthropogenic trace organochlorines including PCBs and DDE. Little is known about the sources, behaviour and effects of natural trace organic chemicals. This manuscript presents an overview on the occurrence of trace organic chemicals in different compartments of the aquatic environment. Important knowledge gaps with regards to trace chemicals in the marine environment are presented.

Animals↗
PubMed2002

Review of the potential use of brown algal ecotoxicological assays in monitoring effluent discharge and pollution in southern Australia.

The temperate near-shore reefs of southern Australasia possess diverse assemblages of brown algal macrophytes which underpin major grazing and detrital food chains in medium to high energy coastal habitats. These 'kelp' communities are at risk from effluent discharge with documented decline of macrophyte stands in areas subject to outfall. Recent studies utilising reproductive endpoints of several Australian species in ecotoxicological assays have highlighted their sensitivity to pollution. Results indicate an acceptable degree of reproducibility for assays with variation in response between taxa presumably related to differing habitat requirements and potential for stress resulting from toxicant/pollution exposure. Species studied are drawn from the orders Laminariales and Fucales, with the latter in particular offering substantial scope for further investigation. The greatest diversity of fucoid algae is found in south-eastern Australia and closely related taxa occur in similar latitudes in both the southern and northern hemispheres. The broad distribution of taxa from both taxonomic groups enables ready comparison of assays from disparate locations and offers the potential for simple, routine toxicological testing and habitat monitoring across broad geographic ranges.

Australia↗
PubMed2000

Contaminant-induced immunosuppression and mass mortalities among harbor seals.

Virus-associated mass mortalities among seals inhabiting northwestern Europe have generated an interest in immunotoxicology in this species. A morbillivirus has been isolated from victims, but a contribution of immunotoxic contaminants to the severity of the outbreaks could not be ruled out. Fish-eating seals occupy high trophic levels in the aquatic food chain, and accumulate high levels of contaminants including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). Such chemicals have been found to be immunotoxic at low doses in studies of laboratory animals. We carried out an immunotoxicological study, in which captive harbor seals (Phoca vitulina) were fed herring from either relatively uncontaminated sites of the Atlantic Ocean, or from the highly contaminated Baltic Sea. In this report we summarize the contaminant-related immunosuppression observed in the captive group of seals fed herring from the Baltic Sea. In addition, we describe two parallel studies, in which laboratory rats are exposed as adults or perinatally to the contaminants in the Baltic Sea herring, exhibiting immunotoxicity. On the basis of these studies we conclude that complex mixtures of environmental contaminants including PCBs, PCDFs, and PCDDs may represent a real immunotoxic risk to free-ranging seals.

Animals↗
PubMed2002

Food web structure in the recently flooded Sep Reservoir as inferred from phytoplankton population dynamics and living microbial biomass.

Phytoplankton dynamics, bacterial standing stocks and living microbial biomass (derived from ATP measurements, 0.7-200 mm size class) were examined in 1996 in the newly flooded (1995) Sep Reservoir ('Massif Central,' France), for evidence of the importance of the microbial food web relative to the traditional food chain. Phosphate concentrations were low, N:P ratios were high, and phosphate losses converted into carbon accounted for <50% of phytoplankton biomass and production, indicating that P was limiting phytoplankton development during the study. The observed low availability of P contrasts with the high release of "directly" assimilable P often reported in newly flooded reservoirs, suggesting that factors determining nutrient dynamics in such ecosystems are complex. The phosphate availability, but also the water column stability, seemed to be among the major factors determining phytoplankton dynamics, as (i) large-size phytoplankton species were prominent during the period of increasing water column stability, whereas small-size species dominated phytoplankton assemblages during the period of decreasing stability, and (ii) a Dinobryon divergens bloom occurred during a period when inorganic P was undetectable, coinciding with the lowest values of bacterial standing stocks. Indication of grazing limitation of bacterial populations by the mixotrophic chrysophyte D. divergens (in late spring) and by other potential grazers (mainly rotifers in summer) seemed to be confirmed by the Model II or functional slopes of the bacterial vs phytoplankton regressions, which were always <0.63. Phytoplankton biomass was not correlated with phosphorus sources and its contribution was remarkably low relative to the living microbial biomass which, in contrast, was positively correlated with total phosphorus in summer. We conclude that planktonic microheterotrophs are strongly implicated in the phosphorus dynamics in the Sep Reservoir, and thus support the idea that an important amount of matter and energy flows through the "microbial loop" and food web, shortly after the flooding of a reservoir.

Bacteria↗
PubMed2001

Thin-film solid-phase extraction to measure fugacities of organic chemicals with low volatility in biological samples.

To investigate the environmental fate, food chain bioaccumulation, and toxicity of organic chemicals, it is often preferable to measure the chemical's fugacity rather than its concentration. However, simple methods to do this are rare. This paper presents a novel yet simple method to measure fugacities of a range of poorly volatile hydrophobic organic chemicals ranging in octanol-air partition coefficients from 10(5.6) to 10(9.2). Thin films of ethylene vinyl acetate coated on glass surfaces are used as solid-phase samplers of contaminated biological tissues. The technique is applied to fish tissue samples and spiked fish diets to determine method feasibility, equilibration times, reproducibility, and property characteristics of the thin films. It is concluded that the method provides an attractive technique to measure chemical fugacities in biological tissues without requiring solvent extractions and cleanup. The method is further expected to be applicable to investigate the fugacity of semivolatile and poorly volatile organic chemicals in air, water, sediments, and soil.

Chemistry Techniques, Analytical↗
PubMed2004

Radionuclide migration modeling through the soil-plant system as adapted for Hungarian environment.

The migration of radionuclides released as fallout through the food-chain to humans was modelled using the MODELMAKER software. In the established dynamic environmental transfer model ETM-2002 with compartmental structure, the principal pathways of vegetable contamination were studied specifically for the Hungarian environment. These pathways were: direct deposition on plant surface, root uptake and deposition after resuspension from the soil surface. As result of the modeling the variation of activity-concentration with time was obtained in the compartments. The validation of the model was done by comparing the calculated results with those obtained in field experiments. A sensitivity analysis of the input parameters was also carried out and the parameters were categorized by their sensitivity index (SI). According to this study, the most sensitive parameters are the daily human intake of vegetable, the distribution coefficient, the transfer factor from soil to plant and the weathering half-time. The most probable distribution types for the parameter values were also determined based on Monte Carlo simulations.

Animals↗
PubMed2002

Lead within ecosystems on metalliferous mine tailings in Wales and Ireland.

A comparative study of the concentrations of lead in ecosystems developed on metalliferous mine tailings was undertaken. Mine soils, vegetation, ground-dwelling invertebrates and Apodemus sylvaticus from nine abandoned mines in Wales and a modern Irish mine site were sampled in order to evaluate and compare exposure risks to wildlife. The mine sites had a wide range of relatively high concentrations of total lead in their tailings (from 1058 to 46,630 mg kg(-1)) but the extractable lead fractions were extremely variable and not clearly related or proportional to the total values. The high soil concentrations were reflected in vegetation collected from most of the sites with the exception of the modern mine, but there was no statistical relationship, on a site basis, between available soil lead and that in plant leaf samples. The highest plant concentrations were found in litter, which in all but one of the Welsh sites exceeded the threshold guideline value of 150 mg kg(-1). Food-chain transfer was shown by high concentrations of lead in invertebrates and A. sylvaticus from the abandoned Welsh mines. A highly significant relationship existed between lead in grass and the grasshopper, Chorthippus brunneus. Adverse effects on soil invertebrates, essential to the decomposition processes and cycling of essential nutrients, were identified as probably the major obstacle to natural ecosystem development on the abandoned Welsh sites. Toxicological risk of lead to the small mammals from the Welsh sites, but not the modern Irish tailings, is indicated given the high lead concentrations in dietary items and the resultant residues in kidney with some evidence of renal oedema in animals from two sites. The absence of a significant relationship between the estimated dietary lead concentration. calculated on a site basis, and the total body concentration in A. sylvaticus, was attributed, in part, to the large size of the home range and the partial feeding of individual animals off the contaminated mine site.

Animals↗
PubMedDate not supplied

Heavy metal determination in aquatic species for food purposes.

New analytical procedures and sample mineralizations are proposed regarding the determination of arsenic, selenium, copper, lead, cadmium, zinc and mercury in matrices involved in food chain as mussel, clams and fishes. As regard As, Se, Cu, Pb, Cd and Zn determinations, H2SO4-HNO3 acidic mixture is used for the digestion of each matrix. In the case of Hg the sample digestion is performed using a concentrated suprapure H2SO4-K2Cr2O7 mixture and the results are compared with those from other conventional methods. Differential pulse cathodic (DPCSV) and anodic stripping voltammetry (DPASV) are employed for determining simultaneously selenium, arsenic and copper, lead, cadmium, zinc, respectively, while mercury determination is carried out by the cold vapour atomic absorption spectrometry (CV-AAS) with reduction with SnCl2. The voltammetric measurements were performed using a conventional three-electrode cell and the ammonia-ammonium chloride buffer (pH 9.3) as supporting electrolyte. For all the elements, in addition to the detection limits, precision and accuracy data are also reported: the former, expressed as relative standard deviation (Sr), and the latter, expressed as relative error (e), are in all cases between 3 to 6%.

Animals↗
PubMed2004

Platinum group elements in raptor eggs, faeces, blood, liver and kidney.

The increased use of platinum group elements (PGEs) in automobile catalysts and their emission into the environment has led to a concern over environmental and particularly biological accumulation. Specimens of samples from raptors are useful for the investigation of the impact of PGEs because these birds are found in both urban and rural environments and are invariably at the top of the food chain. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations were determined by quadrupole Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in eggs of the sparrowhawk (Accipiter nisus) and the peregrine falcon (Falco peregrinus), and in blood, liver and kidney of the peregrine falcon, while only Pt was determined in faeces of the peregrine falcon and the gyrfalcon (Falco rusticolus). PGE concentrations were higher in blood compared to both faeces and eggs, while liver and kidney concentrations were not elevated indicating no bioaccumulation through metallothionein pathways. A significant spatial trend could only be established for Pt in faeces. The general lack of a spatial trend is probably due to the widespread distribution of automobiles and the long-range transport of nanoparticles containing PGEs, and because birds migrate and forage over large areas. No significant temporal trend could be established. Higher relative concentrations of Pd, followed by Rh and Pt, indicate a mobility gradient of Pd>>Rh>Pt.

Animals↗
PubMed2004

Chlorobenzenes, chlorinated pesticides, coplanar chlorobiphenyls and other organochlorine compounds in Greenland biota.

This paper summarises the levels and composition of chlorobenzenes, chlorinated pesticides, coplanar polychlorinated biphenyls (PCBs) and the chlorinated compounds octachlorostyrene (OCS), hexachlorocyclobutadiene (HCBD) and pentachloro-anisole (PCA) in biota from the terrestrial, freshwater and marine environment of Greenland. The data were obtained during the second phase of the Arctic Monitoring and Assessment Programme (AMAP). Of the chlorobenzenes, hexachlorobenzene was the main constituent detected in almost all samples. The chlorobenzenes accumulate in the marine food web in a similar manner to the better-studied persistent organic pollutants, with maximum concentrations in beluga, minke whale and narwhal. However, concentrations in ringed seals and kittiwakes were lower than in marine fish, contradicting biomagnification. Of the organochlorine pesticides, the drin pesticides (aldrin, endrin, dieldrin) and heptachlor had increasing concentrations along the food chain, whilst biomagnification was less pronounced for endosulfan, methoxychlor and mirex. Endosulfan and methoxychlor are pesticides still in use and considered less persistent than other organochlorine pesticides. Their occurrence in Arctic biota is of particular concern, also given the high acute toxicity of endosulfan to fish. Chlorobenzene and pesticide concentrations tended to be lower in the Greenland samples than in the same animals from the Canadian Arctic, whilst their concentrations were similar to samples from Svalbard and Iceland. However, temporal trends might overlap the geographical differences. Coplanar chlorobiphenyls (CBs) were found in all samples analysed, with the maximum concentrations found in marine mammals such as beluga and narwhal. Biota from the terrestrial environment appeared to be less contaminated. The main contributor on a TEQ basis was CB126. OCS, HCBD and PCA were detected in biota from Greenland, although at very low concentrations. OCS seems to have the widest occurrence and the highest potential for biomagnification of the three compounds analysed.

Animals↗
PubMed2003

A potential vector of domoic acid: the swimming crab Polybius henslowii Leach (Decapoda-brachyura).

The swimming crab Polybius henslowii may play an important role in the movement of the amnesic shellfish toxin, domoic acid (DA), through the marine food chain. High DA concentrations have been determined in crab samples harvested along the Portuguese coast during the summer of 2002, reaching a level of 323.1 microg DA/g crab tissue. Toxin distribution in the different crab organs showed levels as high as 571.6 microg DA/g in the visceral tissues. Levels of toxin 4-12 times lower were detected in the remaining tissues. This crab might be a prominent vector of the toxin to higher trophic levels, including fishes, sea birds and even humans. In Portugal P. henslowii is commercialised during the summer in some local markets. DA concentrations were found close to the legal limit of 20 microg/g in samples purchased at Figueira da Foz market. The crabs are boiled prior to reaching the consumers. The cooking process was evaluated. Determination of toxin losses during the cooking process showed a toxin reduction higher than 50%. DA was determined by HPLC-UV and confirmed by spectra acquired with diode-array detector.

Animals↗
PubMed2003

Assessment of bioconcentration and secondary poisoning of surfactants.

The relevance of the bioconcentration behaviour of surfactants for the secondary poisoning assessment and for the risk characterisation in the bird and mammalian food chain has been investigated. The approach used is described in the recently revised EU Technical Guidance Document for the Risk Assessment of Substances. The results demonstrate that, based on experimentally derived bioconcentration factors, environmental concentrations and effects in animals, there is a clear level of safety for both linear alkylbenzene sulphonate (LAS) and alcohol ethoxylates (AE), the most important surfactants by volume. To assess other surfactants used in detergents, a bioconcentration factor that would need to be attained for secondary poisoning to be of concern has been estimated from predicted environmental concentrations and known long-term effects data in animals. Based on the known structural similarity of these surfactants to LAS and AE and the ubiquitous nature of the enzymatic systems that are present in biotransformation processes in organisms, it is concluded that bioconcentration of these surfactants to these levels is highly unlikely. Therefore the potential for secondary poisoning effects of these surfactants is extremely low.

Animals↗
PubMed2004

Experimental system to displace radioisotopes from upper to deeper soil layers: chemical research.

BACKGROUND: Radioisotopes are introduced into the environment following nuclear power plant accidents or nuclear weapons tests. The immobility of these radioactive elements in uppermost soil layers represents a problem for human health, since they can easily be incorporated in the food chain. Preventing their assimilation by plants may be a first step towards the total recovery of contaminated areas. METHODS: The possibility of displacing radionuclides from the most superficial soil layers and their subsequent stabilisation at lower levels were investigated in laboratory trials. An experimental system reproducing the environmental conditions of contaminated areas was designed in plastic columns. A radiopolluted soil sample was treated with solutions containing ions normally used in fertilisation (NO3-, NH4+, PO4--- and K+). RESULTS: Contaminated soils treated with an acid solution of ions NO3-, PO4--- and K+, undergo a reduction of radioactivity up to 35%, after a series of washes which simulate one year's rainfall. The capacity of the deepest soil layers to immobilize the radionuclides percolated from the superficial layers was also confirmed. CONCLUSION: The migration of radionuclides towards deeper soil layers, following chemical treatments, and their subsequent stabilization reduces bioavailability in the uppermost soil horizon, preventing at the same time their transfer into the water-bearing stratum.

Accidents↗
PubMed2001

Organochlorine pesticide levels in maternal adipose tissue, maternal blood serum, umbilical blood serum, and milk from inhabitants of Veracruz, Mexico.

Organochlorine pesticides, due to their persistence, accumulate in food chains and cause elevated contamination in human beings. These residues bioconcentrate in lipid-rich tissues according to the equilibrium pattern of internal transport and lipid tissue content. The analyses of maternal adipose tissue, maternal blood serum, umbilical blood serum, colostrum, and mature milk indicate circulation of these compounds through all compartments of the maternal body, including their crossover of the placental barrier. The greatest residue levels found correspond to DDTs, with highest levels determined in colostrum (5.71 mg/kg of DDT total), followed by adipose tissue with 5.66 mg/kg and in mature milk with 4.70 mg/kg. Among DDTs, pp'DDE is the most predominant compound. The paired analyses of organochlorine pesticide residue levels between mother blood serum and umbilical blood serum demonstrate significant correlation and their transfer from mother to fetus through the placenta. The paired analyses of adipose tissue and colostrum and mature milk contamination levels indicate a high degree of coherence, principally of DDT, in the body and lactation as a decontamination means.

Adipose Tissue↗
PubMed2005

Distribution of microcystins in a lake foodweb: no evidence for biomagnification.

Microcystins, toxins produced by cyanobacteria, may play a role in fish kills, although their specific contribution remains unclear. A better understanding of the eco-toxicological effects of microcystins is hampered by a lack of analyses at different trophic levels in lake foodwebs. We present 3 years of monitoring data, and directly compare the transfer of microcystin in the foodweb starting with the uptake of (toxic) cyanobacteria by two different filter feeders: the cladoceran Daphnia galeata and the zebra mussel Dreissena polymorpha. Furthermore foodwebs are compared in years in which the colonial cyanobacterium Microcystis aeruginosa or the filamentous cyanobacterium Planktothrix agardhii dominated; there are implications in terms of the types and amount of microcystins produced and in the ingestion of cyanobacteria. Microcystin concentrations in the seston commonly reached levels where harmful effects on zooplankton are to be expected. Likewise, concentrations in zooplankton reached levels where intoxication of fish is likely. The food chain starting with Dreissena (consumed by roach and diving ducks) remained relatively free from microcystins. Liver damage, typical for exposure to microcystins, was observed in a large fraction of the populations of different fish species, although no relation with the amount of microcystin could be established. Microcystin levels were especially high in the livers of planktivorous fish, mainly smelt. This puts piscivorous birds at risk. We found no evidence for biomagnification of microcystins. Concentrations in filter feeders were always much below those in the seston, and yet vectorial transport to higher trophic levels took place. Concentrations of microcystin in smelt liver exceeded those in the diet of these fish, but it is incorrect to compare levels in a selected organ to those in a whole organism (zooplankton). The discussion focuses on the implications of detoxication and covalent binding of microcystin for the transfer of the toxin in the foodweb. It seems likely that microcystins are one, but not the sole, factor involved in fish kills during blooms of cyanobacteria.

Animals↗
PubMed2002

Can helminth community patterns be amplified when transferred by predation from intermediate to definitive hosts?

Helminth communities in definitive hosts are formed by the acquisition of packets of larvae arriving each time an intermediate host is consumed. It is thus possible that associations between parasite species or other aspects of community structure get transferred from intermediate to definitive hosts. Earlier computer simulations showed that associations between 2 parasite species, in particular positive associations, could be transferred up the food chain. Here, we alter some of the assumptions of previous models and generate new simulations of several ways in which source infracommunities in intermediate hosts can be transferred to target infracommunities in definitive hosts. In particular, we introduced nonrandom selection of intermediate hosts by predatory definitive hosts, to mimic the phenomenon of host manipulation by parasites; this consisted in biasing predation toward intermediate hosts harboring a certain parasite species. Overall, our results show that positive covariances between 2 parasite species can not only be transferred but can also be amplified during transmission to definitive hosts; significant covariance between parasite species can even appear in the definitive hosts when none existed in the intermediate hosts. Negative covariance was not as readily transferred to definitive hosts and amplified, in part because of properties of the presence-absence covariance index. Amplification of covariance results from intermediate host manipulation as well as from other processes taking place during transmission. These results suggest that the patterns of association between helminth species in definitive hosts cannot be taken to reflect the processes acting inside those hosts: they may simply be inherited, with amplification, from intermediate hosts.

Animals↗
PubMed2004

Development of a model microbial predator-prey system suitable for studies of the behavior of toxic trace metals.

Interactions between microbial predators and their prey can significantly influence the behavior of toxic trace metals. Ingested bacterial prey-bound metals can either accumulate within a predator or be excreted and potentially reintroduced into the dissolved phase. A defined predator-prey system suitable for developing a more fundamental understanding of metal behavior in simple microbial food chains was designed and tested by using lead (Pb) as a representative cationic transition metal. Desired features of this system were the ability to define the chemical speciation of dissolved metals as well as to distinguish between prey- and predator-bound metals. Pseudomonas putida and the ciliate protozoan Tetrahymena thermophila were selected as representative bacterial prey and predator species, respectively. In addition, the use of fluorescent microspheres was evaluated as an experimental surrogate for bacterial prey. Filtration techniques for size-selective separation were developed so that the distribution of Pb between cells of T. thermophila, cells of P. putida or microspheres, and the dissolved phase could be assessed. Filtration units were selected based on their ability to perform separations with minimal metal loss at circumneutral pH. Five-micron polycarbonate filter membranes successfully separated T. thermophila from P. putida with good cell retention and low metal loss. Centrifuge filters successfully separated dissolved and particle-bound metal (<5,000 nominal molecular wt limit). Exemplary experimental results are presented and show that predation on Pb-exposed cells of P. putida or microspheres increases uptake of Pb by T. thermophila.

Animals↗
PubMed2000

The potential for the control of Escherichia coli O157 in farm animals.

The presence of Escherichia coli O157 in the faeces of farm animals appears to provide a primary route for human infection, either through physical contact or by contamination of the food chain. Controlling the survival and proliferation of this pathogen in the ruminant gut could offer a measure of protection in the short term, and ultimately complement alternative biotechnological based solutions. Normally, E. coli is greatly outnumbered in the ruminant gut by anaerobic bacteria, producers of weak acids inhibitory to the growth of this species. Withdrawal of feed prior to animal slaughter reduces the concentration of these acids in the gut and may be accompanied by the proliferation of E. coli. There are conflicting reports concerning the effects of changes in the ruminant diet upon faecal shedding of E. coli O157. It is contended that it is important to identify animal husbandry methods or feed additives that may be accompanied by an increased risk of proliferation of this pathogen. Greater understanding of the mechanisms involved in bacterial survival in the presence of weak acids, in the interactions between E. coli and other gut bacteria, and of the effects of some antibacterial plant secondary plant compounds on E. coli, could lead to the development of novel control methods.

Animal Feed↗