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PubMed2003

The distribution of octachlorostyrene (OCS) in environmental samples from Europe.

Although octachlorostyrene (OCS) was never used as a commercial product, it may be produced during incineration and combustion processes involving chlorinated compounds. Its environmental spreading was evaluated through the analysis of several representative samples. OCS could not be measured in soil samples collected from urban and rural areas or sediments, but was present (up to 5.41 ng/g dry weight) in industrial soil collected near chemically polluted areas. For aquatic biota samples, the OCS concentrations in freshwater mussels ranged from <0.01 ng/g wet weight (ww) to 0.18 ng/g ww (mean 0.06 ng/g ww) and similar levels could be measured in 11 freshwater fish species from Belgium and Romania. A higher OCS contamination level was found in shrimps (mean 0.08 ng/g ww) compared to marine fish (mean 0.02 ng/g ww for bib and 0.01 ng/g ww for sole and whiting, respectively). OCS could also be measured in 19 harbour porpoise (Phocoena phocoena) liver samples with a mean value of 1.90 ng/g ww. According to these data, it could be computed that the biomagnification factor for OCS was one order of magnitude lower than that of HCB in the fish-porpoise food chain. The mean OCS concentrations in blue tits (Parus caeruleus) eggs and great tits (Parus major) adipose tissue were 1.24 ng/g ww and 3.24 ng/g ww, respectively. OCS could be measured in different tissues of hedgehog (Erinaceus europaeus), with the highest concentrations found in adipose tissue (mean 0.34 ng/g ww) and liver (mean 0.39 ng/g ww). In contrast, only low concentrations of OCS could be measured in human adipose tissue (up to 0.38 ng/g ww) and liver (up to 0.05 ng/g ww), while it could not be detected in human brain or lung. The relationship between the concentrations of OCS and HCB was also discussed for each species.

Adipose Tissue↗
PubMed2002

Survival of Cryptosporidium parvum oocysts recovered from experimentally contaminated oysters (Ostrea edulis) and clams (Tapes decussatus).

Samples of two species of shellfish that form part of the human food chain (the oyster Ostrea edulis and the marine clam Tapes decussatus) were experimentally contaminated with Cryptosporidium parvum oocysts. Changes in the viability of oocysts subsequently recovered from the shellfish were evaluated by means of an immunofluorescent antibody technique (IFAT) and inclusion/exclusion of the fluorogenic vital dye propidium iodide. There was a sharp decrease in oocyst viability during the first 4 days, with 15-25% viable oocysts remaining thereafter. In addition the infectivity of these oocysts at 10 and 31 days post-contamination was demonstrated using a suckling murine model.

Animals↗
PubMed2006

Biomagnification of PBDEs and PCBs in food webs from the Baltic Sea and the northern Atlantic Ocean.

Biomagnification of polychlorinated biphenyls (PCBs) and polybrominated diphenylethers (PBDEs) in food webs from the Baltic Sea and the northern Atlantic Sea was investigated. For this, we used PCB and PBDE concentration data, together with data on fish body weight and delta15N of fish and zooplankton as a measure of trophic position. In the Baltic Sea material, consisting of zooplankton, sprat, herring and salmon, we report biomagnification of all PCB congeners but PCB #209 and of PBDEs with 3-6 or 7 bromine atoms. Higher brominated PBDEs and PCB 209 did not biomagnify likely due to their high molecular weights or sizes and subsequent inefficient dietary uptake in fish. If salmon was excluded from the statistical analysis, strong biomagnification of PCB #209 was evident, indicating species differences in biomagnification. In the Baltic Sea material delta15N and body weight covaried. In the Atlantic Sea material, consisting of fish samples (herring and salmon) of larger body sizes, we show positive correlation between concentrations of most PCBs and PBDEs and body weight without increasing delta15N. This shows that biomagnification in some cases depends on body size and not trophic position. We conclude that there probably is trophic position dependence in biomagnification, which was manifested in a food chain from zooplankton to piscivores, but no further trophic position influence on biomagnification in fish at the highest trophic levels. In these fish, there was a body size effect leading to biomagnification, probably due to slower clearance in larger fish. PCB concentrations were generally between 2 and 6 times higher in Baltic Sea salmon than in Atlantic Sea salmon. Higher PBDE concentrations in the Baltic compared to the Atlantic Sea salmon were also found, but with a larger variation between congeners. Nona- to deca-BDEs were found in most investigated samples, which illustrates the bioavailability of these compounds. Unidentified penta-, hexa-, hepta-, and octa- BDEs were found in several samples.

Animals↗
PubMed2001

Persistent organochlorine levels in six prey species of the gyrfalcon Falco rusticolus in Iceland.

Our previous investigations have revealed very high levels of organochlorines (OCs) in the Icelandic gyrfalcon Falco rusticolus, a resident top predator. We now examine six potential prey species of birds, both resident and migratory, in order to elucidate the most likely route of the OCs to the gyrfalcon. The ptarmigan Lagopus mutus, the most important prey of the gyrfalcon, contained very low levels of OCs. Bioaccumulation of polychlorinated biphenyls (PCBs) and DDTs in mallards Anas platyrhynchos, tufted ducks Aythya fuligula, golden plovers Pluvialis apricaria, purple sandpipers Calidris maritima, and black guillemots Cepphus grylle reflected their position in the foodchain. The differences in OC-levels seem nevertheless too high just to reflect the different food-chain levels of these species in Iceland. The winter grounds of the migratory golden plovers and tufted ducks appear to be more contaminated than the Icelandic terrestrial habitat of ptarmigans or the freshwater habitat as reflected in mallards, both resident species. However, spending the winter on the coast in Iceland, results in high levels of contaminants in purple sandpipers and black guillemots. Our results indicate OC contamination of the marine ecosystem in Iceland while the terrestrial and freshwater ecosystems are little affected. It is postulated that gyrfalcons receive the major part of the observed contamination from prey other than ptarmigan, especially birds associated with the marine ecosystem and also from migratory birds.

Animals↗
PubMed2005

Accumulation of organotin compounds in the deep-sea environment of Nankai Trough, Japan.

The concentration of butyltin (BT) and phenyltin (PT) compounds was measured in sediment, gastropods (Colliloconcha nankaiensis), sea cucumbers (Psychropotes verrucosa), galatheid crabs (Munidopsis albatrossae and Munidopsis subsquamosa), and bivalves (Clyptogena tsubasa and Clyptogena nautilei) collected from the Nankai Trough (water depth about 3000 m). Sediment at depths of up to 1 cm was taken by a core sampler and at depths of up to 15 cm was taken by rake. The concentration of BTs in sediment core from a depth of 0-1 cm (0.041 mg kg(-1) dry) was higher than in sediment core from 0-15 cm (0.021 mg kg(-1) dry). The relative proportion of different BTs in the 0-1-cm sediment core was similar to that in the 0-15-cm sediment core, but the concentration of PTs in the former (0.028 mg kg(-1) dry) was lower than in the latter 0-15 cm (0.052 mg kg(-1) dry). Organotin (OT) compounds were also detected in deep-sea organisms. The means of BT concentrations in C. nankaiensis, P. verrucosa, M. albatrossae, M. subsquamosa, Cl. tsubasa, and Cl. nautilei were, respectively, 0.089, 0.057, 0.018, 0.016, 0.019, and 0.026 mg kg(-1). The corresponding concentrations of PTs were 0.212, 0.363, 0.166, 0.186, 0.030, and 0.025 mg kg(-1). High concentrations of BTs and PTs were observed in gastropods and sea cucumbers. The species of deep-sea organism can be classified by delta(13)C value into two groups (A and B). The organisms in group A use organic matter chemosynthesized by symbiotic bacteria while those in group B depend on photosynthesis carried out near the surface by phytoplankton. No difference in BT or TBT concentration is observed between the two groups, but PT and TPT concentrations are higher in group B. Trophic levels in the food chain are often estimated using delta(15)N values. Group B showed a higher trophic level than group A. Although no change in BT and TBT concentration was observed to accompany increases of delta(15)N values, PT and TPT concentrations generally increased with increasing delta(15)N values. The compositions of BTs in deep-sea organisms were calculated. An increasing proportion of MBT and a declining proportion of DBT were observed at higher trophic levels. No correlation between the shell length of Cl. nautilei and BT or PT concentration was observed. The average partition coefficients of TBT for C. nankaiensis, P. verrucosa, M. albatrossae, M. subsquamosa, Cl. Tsubasa, and Cl. nautilei were 2.6, 0.72, 0.63, 0.19, 0.43, 0.30, and 0.46.

Animals↗
PubMed2003

The epidemics of bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease: current status and future prospects.

The large epidemic of bovine spongiform encephalopathy (BSE) in the United Kingdom has been in decline since 1992, but has spread to other countries. The extensive control measures that have been put in place across the European Union and also in Switzerland should have brought the transmission of BSE under control in these countries, provided that the measures were properly enforced. Postmortem tests on brain tissue enable infected animals to be detected during the late stages of the incubation period, but tests that can be performed on live animals (including humans) and that will detect infections early are urgently needed. The number of infected animals currently entering the food chain is probably small, and the controls placed on bovine tissues in the European Union and Switzerland should ensure that any risks to human health are small and diminishing. Vigilance is required in all countries, especially in those in which there has been within-species recycling of ruminant feed. Fewer than 150 people, globally, have been diagnosed with variant Creutzfeldt-Jakob disease (vCJD), but there are many uncertainties about the future course of the epidemic because of the long and variable incubation period. Better control measures are necessary to guard against the possibility of iatrogenic transmission through blood transfusion or contaminated surgical instruments. These measures will required sensitive and specific, diagnostic tests and improved decontamination methods.

Animals↗
PubMed2003

Habitat fragmentation resulting in overgrazing by herbivores.

Habitat fragmentation sometimes results in outbreaks of herbivorous insect and causes an enormous loss of primary production. It is hypothesized that the driving force behind such herbivore outbreaks is disruption of natural enemy attack that releases herbivores from top-down control. To test this hypothesis I studied how trophic community structure changes along a gradient of habitat fragmentation level using spatially implicit and explicit models of a tri-trophic (plant, herbivore and natural enemy) food chain. While in spatially implicit model number of trophic levels gradually decreases with increasing fragmentation, in spatially explicit model a relatively low level of habitat fragmentation leads to overgrazing by herbivore to result in extinction of the plant population followed by a total system collapse. This provides a theoretical support to the hypothesis that habitat fragmentation can lead to overgrazing by herbivores and suggests a central role of spatial structure in the influence of habitat fragmentation on trophic communities. Further, the spatially explicit model shows (i) that the total system collapse by the overgrazing can occur only if herbivore colonization rate is high; (ii) that with increasing natural enemy colonization rate, the fragmentation level that leads to the system collapse becomes higher, and the frequency of the collapse is lowered.

Animals↗
PubMed2006

Marine birds as indicators of Arctic marine ecosystem health: linking the Northern Ecosystem Initiative to long-term studies.

Marine birds are sensitive indicators of the condition of marine ecosystems in the Arctic, partly because they feed at the top of the arctic food chain. The Northern Ecosystem Initiative (NEI) recently supported four separate studies that investigated aspects of Arctic marine bird science which simultaneously addressed goals of the NEI to better understand northern ecosystems and their response to environmental stressors. The projects used both scientific and traditional knowledge to examine the relationship between sea-ice, contaminants, and the ecology of marine birds, and to transfer environmental knowledge to students. Results from these investigations confirm that changes are occurring in Arctic environments, and that these are captured through marine bird research. Collectively these studies provided new data that supported NEI objectives of monitoring the health of the Arctic ecosystem, and contributed to Canada's international obligations for Arctic science.

Animals↗
PubMedDate not supplied

[Model of "standing water" of Baikalian phytoplankton interannual dynamics].

A "standing waves" model is presented which is based on the idea that an energy impulse accumulated from the spring bloom outburst of phytoplankton moves along a food chains. When its "echo" comes back, it generates a new bloom outburst, and a next cycle occurs. It is supposed that the resonance of self-supporting oscillations in populations with periodic solar influences led to standing waves, which provide for biosystem stability and cyclic recurrence of phytoplankton bloom. To test the model, an analysis of the interannual dynamics (from 1941 to 1998) of the pelagic phytoplankton in the southern basin of the lake Baikal was carried out. The discovered 11-year cycles with 3 2/3-year cycles within them conform well to the model, which made it possible to explain not only the cyclic recurrence but also a number of other obscure aspects of phytoplankton life in the lake Baikal. The next bloom burst is predicted to take place in 2001.

Food Chain↗
PubMed2006

Biomass, size, and trophic status of top predators in the Pacific Ocean.

Fisheries have removed at least 50 million tons of tuna and other top-level predators from the Pacific Ocean pelagic ecosystem since 1950, leading to concerns about a catastrophic reduction in population biomass and the collapse of oceanic food chains. We analyzed all available data from Pacific tuna fisheries for 1950-2004 to provide comprehensive estimates of fishery impacts on population biomass and size structure. Current biomass ranges among species from 36 to 91% of the biomass predicted in the absence of fishing, a level consistent with or higher than standard fisheries management targets. Fish larger than 175 centimeters fork length have decreased from 5% to approximately 1% of the total population. The trophic level of the catch has decreased slightly, but there is no detectable decrease in the trophic level of the population. These results indicate substantial, though not catastrophic, impacts of fisheries on these top-level predators and minor impacts on the ecosystem in the Pacific Ocean.

Animals↗
PubMed2006

Sustainable ecosystem management using optimal control theory: part 1 (deterministic systems).

The concept of sustainability, an abstract one by its nature, has been given a mathematical representation through the use of Fisher information as a measure. It is used to propose the sustainability hypotheses for dynamical systems, which has paved the way to achieve sustainable development through externally enforced control schemes. For natural systems, this refers to the task of ecosystem management, which is complicated due the lack of clear objectives. This work attempts to incorporate the idea of sustainability in ecosystem management. The natural regulation of ecosystems suggests two possible control options, top-down control and bottom-up control. A comparison of these two control philosophies is made on generic food chain models using the objectives derived from the sustainability hypotheses. Optimal control theory is used to derive the control profiles to handle the complex nature of the models and the objectives. The results indicate a strong relationship between the hypotheses and the dynamic behavior of the models, supporting the use of Fisher information as a measure. As regards to ecosystem management, it has been observed that top-down control is more aggressive but can result in instability, while bottom-up control is guaranteed to give a stable and improved dynamic response. The results also indicate that bottom-up control is a better option to affect shifts in the dynamic regimes of a system, which may be required to recover the system from a natural disaster like the hurricane Katrina.

Animals↗
PubMed2004

Overview of the Belgian programme for the surveillance of the territory and the implications of the international recommendations or directives on the monitoring programme.

The Royal Decree of 20th July has entrusted the Federal Agency for Nuclear Control (FANC) with the task of controlling the territorial radioactivity and the doses received by the population. Within this agenda, a monitoring programme has been developed over many years, in order to follow the main potential exposure pathways of the population. In practice, several potential vectors of contamination are controlled: air (and rain), surface water (including sediments and biota), soils around nuclear installations, food chain, drinking water etc. To carry out such work, the FANC has collaborated with public or private reputable organisations: The Centre of Nuclear Energy Studies of Mol, The National Institute of Radionuclides of Fleurus, and The Louis Pasteur Public Health Institute of Brussels. A synthesis of this monitoring programme will be presented and the most important deductions will be pointed out. For many years, the tendency has been for tighter control of artificial and natural radioactivity in the environment. This has been achieved by increasingly stringent regulations, regarding environmental monitoring efforts, from international organisations (EC, OSPAR, IAEA). In this context, the FANC in Belgium, is involved in a process that will lead to the adaptation of the Belgian monitoring programme. Different aspects of these adaptations and of their consequences will be presented for illustrative purposes.

Belgium↗
PubMed2005

Mercury transfer from fish carcasses to scavengers in boreal lakes: the use of stable isotopes of mercury.

Scavengers play an important role in the flow of energy, matter and pollutants through food webs. For methylmercury (MeHg), which biomagnifies along food chains, the movement of this metal from fish carcasses to aquatic scavengers has never been demonstrated. We measured the transfer of MeHg from fish carcasses to scavenging leeches in two lakes and in the laboratory. The results of a field experiment indicated that leeches were attracted to fish carcasses and that their Hg concentrations increased by as much as a factor of 5 during the time that Hg-rich fish were available for consumption. Under controlled conditions, we exposed leeches to (202)Hg-labelled fish that had been marked in situ following a whole lake (202)Hg addition. Leeches rapidly accumulated Hg from carcasses, and within two weeks assumed the isotopic signature of the carcasses. Necrophagous invertebrates could therefore return Hg from fish carcasses to other trophic levels in lakes.

Animal Feed↗
PubMed2002

About the assumption of linearity in soil-to-plant transfer factors for uranium and thorium isotopes and 226Ra.

The linearity assumption for soil and plant concentrations of radionuclides is usually a good approximation for use in food-chain models. To verify this assumption, different samples of plant and substrate were collected from a granitic zone located near a disused uranium mine in order to cover a large range of concentrations. In all of the samples, the activity concentration of 226Ra and of different isotopes of uranium (238U and 234U) and thorium (232Th, 230Th and 228Th) were determined. The results indicate that the linearity assumption can be considered valid when the range of concentrations taken into account is large (approx. two orders of magnitude). Otherwise, there is a clear deviation from linearity. Also, the influence of different stable elements on the soil-plant transfer factors was studied by using multivariate regression methods. The uptake of uranium, thorium and radium was found to be mainly associated with the concentration of iron in the plant and the phosphorus and alkaline earths in the substrate.

Food Chain↗
PubMed2006

226Ra concentration in the teeth of habitants of areas with high level of natural radioactivity in Ramsar.

The level of natural radiation in some regions of Ramsar, a northern coastal city of Iran, is known to be among the highest levels of natural radiation in the world. 226Ra existing in high concentrations in the soil of this region is washed by underground water and transferred to the surface. In this way, 226Ra enters the food chain of residents and substitutes within the hard body tissues of humans. 226Ra is one of the so-called bone seekers as its metabolic processes in the human body are similar to calcium and remains in hard tissues of body because of its long half-life, and being an alpha emitter causes dangerous effects on human health. The purpose of this study is to determine the concentration of 226Ra in the teeth of residents of these high-level natural radiation areas, compared with a control group. Thirteen teeth in five groups were studied as the case group and thirteen teeth in five corresponding control groups were inspected. The mean values of the activity of 226Ra in the case group and in the control group were 0.32 and 0.18mBqg(-1), respectively.

Case-Control Studies↗
PubMed2002

Environmental processes affecting plant root uptake of radioactive trace elements and variability of transfer factor data: a review.

Soil-to-plant transfer factors are commonly used to estimate the food chain transfer of radionuclides. Their definition assumes that the concentration of a radionuclide in a plant relates linearly solely to its average concentration in the rooting zone of the soil. However, the large range of transfer factors reported in the literature shows that the concentration of a radionuclide in a soil is not the only factor influencing its uptake by a plant. With emphasis on radiocesium and -strontium, this paper reviews the effects of competition with major ions present in the soil-plant system, the effects of rhizosphere processes and soil micro-organisms on bioavailability, the factors influencing transport to and uptake by roots and the processes affecting long-term uptake rates. Attention is given to summarizing the results of recent novel electrophysiological and genetic techniques which provide a physiologically based understanding of the processes involved in the uptake and translocation of radiocesium and -strontium by plants.

Biological Availability↗
PubMed1999

Metal concentrations in the eggs of endangered Florida scrub-jays from central Florida.

We analyzed metal levels in the eggs of the endangered Florida scrub-jay (Aphelocoma coerulescens), an extremely sedentary and modestly long-lived passerine bird. Eggs were obtained as part of the long-term study of this species at the Archbold Biological Station, located in south central Florida. Following a brief and usually short dispersal, Florida scrub-jays remain in a permanent territory in their scrub oak habitat, where they feed mainly on insects and acorns. As they are low on the food chain and sedentary, we expected levels of contaminants to be comparatively low and to reflect the local environment. No significant yearly differences existed for any metal between eggs collected in 1997 (n = 11) and 1998 (n = 5). Arithmetic mean metal concentrations (whole egg, dry weight) were low for arsenic (34 ppb), cadmium (25 ppb), mercury (74 ppb), and lead (66 ppb), intermediate for chromium (226 ppb), and higher for selenium (1,470 ppb) and manganese (2,230 ppb). Except for the low mercury value, all these means were within the range of mean values reported for a wide range of nonpasserine species, including those at high trophic levels, but are lower than concentrations associated with abnormalities in birds. The three essential elements (chromium, selenium, and manganese) were approximately normally distributed, whereas arsenic, cadmium, lead, and mercury were highly skewed (arithmetic mean much higher than geometric mean).

Animals↗
PubMed2005

Mercury concentrations in fish from forest harvesting and fire-impacted Canadian Boreal lakes compared using stable isotopes of nitrogen.

Total mercury (Hg) concentration was determined in several piscivorous and nonpiscivorous species of fish from 38 drainage lakes with clear-cut, burnt, or undisturbed catchments located in the Canadian Boreal Shield. Mercury concentrations increased with increasing fish trophic position as estimated using stable isotopes of nitrogen (N; r2 = 0.52, 0.49, and 0.30 for cut, reference, and burnt lakes, respectively; p < 0.01). Mercury biomagnification per thousand delta15N varied from 22 to 29% in the three groups of lakes. Mercury availability to organisms at the base of the food chain in lakes with cut catchments was higher than that in reference lakes. In cut lakes, Hg concentrations in fish were significantly related to ratio of the clear-cut area to lake area (or lake volume; r = +0.82 and +0.74, respectively, p < 0.01). Both impact ratios were, in turn, significantly correlated with dissolved organic carbon. These findings suggest that differential loading of organic matter-bound Hg to lakes can affect Hg cycling. In addition, Hg concentrations exceeded the advisory limit for human consumption (0.5 microg/g wet wt) from the World Health Organization in all top predatory species (northern pike, walleye, and burbot) found in cut and in two partially burnt lakes. Thus, high Hg concentrations in fish from forest-harvested and partially burnt lakes may reflect increased exposure to Hg relative to that in lakes not having these watershed disturbances.

Animals↗