Lead reduces shell mass in juvenile garden snails (Helix aspersa)

In an earlier paper examining inherited tolerance to Pb, the shell growth of laboratory-bred offspring of Helix aspersa from contaminated sites was compared with that ofjuveniles from naive populations on dosed and undosed diets. Eight-week-old snails were fed either 500 microg g(-1) Pb or a control food in competitive trials between two populations. In the first series of trials, a parental history of exposure to Pb did not confer any advantage to either of two populations (BI and MI) competing with a na?ve population (LE). whether Pb was present in the diet or not. However, in the analysis of their metal concentrations reported here, LE are found to retain higher levels of Pb in the soft tissues than either BI or MI. Compared to their siblings on the unleaded diet, dosed LE and BI juveniles had lower soft tissue concentrations of Ca and Mg. Although the growth in shell height is unaffected by diet, LE and BI juveniles build lighter shells on the Pb-dosed diet, achieving around 75% of the shell mass of their controls. In contrast, the shell weights of dosed MI juveniles are depressed by only 15% and show no change in the essential metal concentrations of their soft tissues. A second experiment using five populations fed only the dosed food show that the shell weight/soft tissue weight ratios are comparable to the dosed snails of the previous experiment. Building a lighter shell thus appears to be the common response of all Helix populations to a high Pb diet, at least amongst juveniles. The reduction in its mass means that less Ca and Mg is added to the shell and, along with the lowered soft tissue concentrations observed in some populations. may be a consequence of an increased effort to excrete Pb. The possibility that the MI population shows a genotypic adaptation. perhaps as some form of modification of its Ca metabolism, is briefly discussed.     

Magnesium and the deposition of lead in the shell of three populations of the garden snail Cantareus aspersus

The loss of Pb from snail soft tissues may depend on the excretion of Ca, and involve the mobilization of shell Ca. Most sub-adults in three populations of Cantareus aspersus (syn. Cornu aspersum Müller) either failed to add, or lost, shell mass on a diet with 250 μg g⁻¹ Pb. Their failure to mineralize shell extensions occurred irrespective of food consumed, time or dietary Mg. Budgets of metals for 36 individuals in each of two populations showed that Ca loss would account for the reduction in shell mass. Lead concentrations were higher in the reduced shells but this may be a consequence of their smaller mass, rather than its cause. In both populations shell reduction correlated with the total mass of Pb assimilated. Any shell growth may have been dependent on the initial Ca reserve in each snail. Differential movement of Mg, Pb and Ca occurred between the shell and soft tissues.     

Effects of C60 nanoparticle exposure on earthworms (Lumbricus rubellus) and implications for population dynamics

Effects of C₆₀ nanoparticles (nominal concentrations 0, 15.4 and 154 mg/kg soil) on mortality, growth and reproduction of Lumbricus rubellus earthworms were assessed. C₆₀ exposure had a significant effect on cocoon production, juvenile growth rate and mortality. These endpoints were used to model effects on the population level. This demonstrated reduced population growth rate with increasing C₆₀ concentrations. Furthermore, a shift in stage structure was shown for C₆₀ exposed populations, i.e. a larger proportion of juveniles. This result implies that the lower juvenile growth rate due to exposure to C₆₀ resulted in a larger proportion of juveniles, despite increased mortality among juveniles. Overall, this study indicates that C₆₀ exposure may seriously affect earthworm populations. Furthermore, it was demonstrated that juveniles were more sensitive to C₆₀ exposure than adults.     

The Akoya pearl oyster shell as an archival monitor of lead exposure

The Akoya pearl oyster (Pinctada imbricata) was experimentally exposed to (a) constant levels of lead (Pb) at 180 microg L(-1) for nine weeks, or (b) two short term (pulse) exposures of Pb at 180 microg L(-1) (three weeks each) with an intervening depuration period (three weeks), to assess its utility as an (i) accumulative monitor of Pb contamination and an (ii) archival monitor for discriminating constant versus pulsed Pb exposure events. P. imbricata showed similar reductions in growth (based on shell morphology and wet weight) and Pb accumulation patterns for whole tissue and shell in response to both Pb exposure regimes. Thus the whole oyster was deemed an inappropriate accumulative monitor for assessing short-term temporal variation of Pb exposure and effect. However, using secondary ion mass spectrometry, Pb was shown to accumulate in the successively deposited nacreous layers of the shell of P. imbricata, documenting the exposure history of constant versus pulsed Pb events. Patterns of Pb deposition not only reflected the frequency of Pb exposure events but also their relative durations. Thus, the shell of P. imbricata may be employed as a suitable biological archive of Pb exposure.     

Adaptation by an urban population of the snail Helix aspersa to a diet contaminated with lead

Two populations of the garden snail Helix aspersa, from an urban car park and from a semi-rural site, were fed a diet containing 500 microg g(-1) of Pb as PbSO(4). After 2 days, half of each population was removed to a Pb-free diet and half continued on the dosed food, both for 64 days. The snails from the contaminated site had a significantly lower uptake of Pb compared with those from the rural, uncontaminated site. The car park snails also lost Pb more rapidly from their tissues. A second experiment evaluated the effect of a previous exposure to a high Pb diet on Pb uptake. The results suggest that the differences between the two populations are not due to a physiological adaptation, but rather that the car park snails represent an ecotype adapted to a high Pb diet.     

The effect of EDDS and citrate on the uptake of lead in hydroponically grown Matthiola flavida

Root and shoot lead concentrations and the impact of chelating agents on these were investigated in two populations of the novel metallophyte Matthiola flavida. Plants were exposed in hydroponics to Pb(NO₃)₂, supplied alone, or in combination with citric acid, or EDDS. When supplied at concentrations expected to bind about 95% of the Pb in a solution containing 1-μM Pb (1000 μM citrate or 3.1 μM EDDS, respectively), the root and shoot Pb concentrations were dramatically lowered, in comparison with a 1-μM free ionic Pb control exposure. A 1-mM EDDS + 1-μM Pb treatment decreased the plants’ Pb concentrations further, even to undetectable levels in one population. At 100 μM Pb in a 1-mM EDDS-amended solution the Pb concentration increased strongly in shoots, but barely in roots, in comparison with the 1-μM Pb + 1-mM EDDS treatment, without causing toxicity symptoms. Further increments of the Pb concentration in the 1-mM EDDS-amended solution, i.e. to 800 and 990 μM, caused Pb hyperaccumulation, both in roots and in shoots, associated with a complete arrest of root growth and foliar necrosis. M. flavida seemed to be devoid of constitutive mechanisms for uptake of Pb-citrate or Pb-EDDS complexes. Hyperaccumulation of Pb-EDDS occurred only at high exposure levels. Pb-EDDS was toxic, but is much less so than free Pb. Free EDDS did not seem to be toxic at the concentrations tested.     

Outdoor and indoor cadmium distributions near an abandoned smelting works and their relations to human exposure

The relationship of measured or modelled Cd concentrations in soil, house dust and available to plants with human urinary Cd concentrations were assessed in a population living around a Cd/Pb/Zn smelter in the UK. Modelled air concentrations explained 35% of soil Cd variation indicating the smelter contributed to soil Cd loads. Multi-variate analysis confirmed a significant role of biological and life-style factors in determining urinary Cd levels. Significant correlations of urinary Cd with soil, house dust and modelled plant available Cd concentrations were not, however, found. Potential reasons for the absence of clear relationships include limited environmental contact in urban populations; the role of undefined factors in determining exposure; and the limited spatial scope of the survey which did not sample from the full pollution gradient. Further, the absence of any significant relationship indicates that environmental measures provide limited advantage over atmospheric model outputs for first stage human exposure assessment.     

Magnesium and the regulation of lead in three populations of the garden snail Cantareus aspersus

Helicid snails appear to regulate Pb more closely than other toxic metals, though it is reported as the least toxic. No regulatory mechanism has been described in animals, and the possible role of Mg in limiting Pb assimilation is examined here for the first time. Three populations of Cantareus aspersus were fed Pb and Ca with three levels of Mg for up to 64 days. Metal assimilation and production efficiency was calculated for each of 108 snails. Populations differed in their pattern of uptake but soft tissue Pb was unaffected by dietary Mg. The proportion of Pb assimilated did not change as soft tissue concentrations increased, indicating no specific regulatory mechanism. The daily addition of Pb to the soft tissues increases with growth rate suggesting uptake is instead some function of growth or cell turnover. Bioconcentration factors varied with time and are unreliable indicators of an evolved regulatory mechanism for Pb.     

Metal accumulation from contaminated food and its effect on growth of juvenile landsnails Helix engaddensis

Metal accumulation by juvenile landsnails, Helix engaddensis, and its effect on growth rate was studied over a 5-week period of exposure and 2 weeks of recovery. An artificial food contaminated with Cu (4-2500 microg x g(-1)), Cd (50-800 microg x g(-1)), Pb, and Zn (20-12500 microg x g(-1)) was used. During the 7 weeks of the experiment, mortality rates were 20, 27, 30, and 38% among snails fed Cu-, Pb-, Zn-, and Cd-contaminated food, respectively. According to the ability to inhibit growth, metals were found to have the following order: Cd > Zn > Cu = Pb. Inhibitory effects of dietary metals started to be significant from the third week of exposure on. Inhibition of growth by Pb and Cu was found to be reversible, and within the first week of recovery, snails erupted their aestivation and resumed feeding and growth to gain weights similar to those of the control groups. Snails fed Cd- or Zn-contaminated food failed to resume growth during the 2 weeks of recovery. This indicates that in the case of Cu and Pb, growth inhibition was mainly due to starvation due to food rejection and aestivation. On the other hand, growth inhibition caused by Cd and Zn may have been resulting from irreversible toxicity. Therefore, snails were assumed to be sensitive to Cd and Zn but tolerant to Cu and Pb. Accumulation of Cu and Pb was significant only at the highest concentrations. At low and medium concentrations, no signs of accumulation were observed, indicating regulation at these concentrations. Cd and Zn accumulation starts at low concentrations but became significant at medium and high levels indicating accumulation of these metals.     

Variation in the mineral composition of eggs of the snail, Helix aspersa between populations exposed to different levels of metal contamination

The eggs of terrestrial gastropods represent a major investment of resources by the parent, not least in the provision of essential metals. In this experiment 11 populations of Helix aspersa were collected from habitats with different histories of lead exposure and allowed to reproduce in the laboratory. After 4 months on a low metal diet, five four-egg samples were taken from a single clutch of each population and analysed for their metal content. Within-clutch and between population variation in the eggs were measured. No Pb or Cd was detected in any of the eggs. Both trace and essential metals show considerable variation between eggs within the same clutch. Cu levels were consistent across populations while egg Zn was closely correlated with soil Zn. Median Ca and Mg levels show little relation to soil concentrations. However, Ca provision declines with soil Pb across the populations. While the metal content of the eggs appears to be closely regulated, an interaction between Pb and Ca in the parental tissues may mediate the supply of Ca to the eggs.     

Population growth of Euchlanis dilatata (Rotifera): combined effects of methyl parathion and food (Chlorella vulgaris)

In the present work, the combined impact of four concentrations (0, 0.0625, 0.125, and 0.25 mg/L) of methyl parathion and three densities (0.5 x 10(6), 1.0 x 10(6), and 2.0 x 10(6) cells/mL) of the green alga Chlorella vulgaris on the population growth of Euchlanis dilatata was studied. In general, regardless of the food level, an increase in the concentration of methyl parathion resulted in a significant reduction of the maximal population density and rate of population increase. The population growth rate in the controls ranged from 0.248 to 0.298; rates were lower in the presence of the pesticide. At any toxicant concentration, rotifers fed higher algal density showed significantly higher population growth compared with those at lower food levels. An interaction between toxicant and food level was evident on the population growth of E. dilatata. Results have been discussed in light of the protective role of algal density on the toxic effects of insecticides on rotifers and the differences in susceptibility to toxicants between planktonic and littoral rotifers.     

Impact of spiked concentrations of Cd,Pb, As and Zn in growth medium on elemental uptake of Nasturtium officinale (Watercress)

This study is aimed at investigating the impact of water quality on the uptake and distribution of three non-essential and toxic elements, namely, As, Cd and Pb in the watercress plant to assess for metal toxicity. The plant was hydroponically cultivated under greenhouse conditions, with the growth medium being spiked with varying concentrations of As, Cd and Pb. Plants that were harvested weekly for elemental analysis showed physiological and morphological symptoms of toxicity on exposure to high concentrations of Cd and Pb. Plants exposed to high concentrations of As did not survive and the threshold for As uptake in watercress was established at 5 ppm. Translocation factors were low in all cases as the toxic elements accumulated more in the roots of the plant than the edible leaves. The impact of Zn on the uptake of toxic elements was also evaluated and Zn was found to have an antagonistic effect on uptake of both Cd and Pb with no notable effect on uptake of As. The findings indicate that phytotoxicity or death of the watercress plant would prevent it from being a route of human exposure to high concentrations of As, Cd and Pb in the environment.     

Relation between mortality of young walleye (Stizostedion vitreum) and recruitment with different forms of compensation

The relation between mortality of young fish and recruitment is important for assessment of the environmental effects of facilities that kill large numbers of young fish, such as electric power stations and hydropower plants. A simulation model with a bioenergetic growth component was applied to examine the relation between mortality of young and recruitment for walleye (Stizostedion vitreum) with different forms of population regulation, including: food limited growth, food limited growth with size-dependent mortality, and food limited growth with age at maturity dependent on size. With food limited growth small increases in mortality of young reduced recruitment considerably, but the population slowly approached a new equilibrium. If mortality of young increased when growth was food limited, the population approached a new equilibrium of natality and mortality because with fewer individuals there was more food per individual, and individuals were larger in size and produced more eggs; this feedback adjusted natality to equal mortality. With either mortality or age at maturity dependent on size, large increases in mortality of young resulted in only small decreases in recruitment.     

Population-level effects of the neem insecticide, Neemix, on Daphnia pulex

Although natural insecticides from the neem tree are generally perceived as less harmful to the environment than synthetic insecticides, new evidence indicates that these products may pose a risk to certain nontarget organisms. In this paper, acute and chronic effects of commercial neem insecticides on the aquatic invertebrate, Daphnia pulex were examined. The acute toxicity of two commercial neem insecticides, Neemix, Azatin and the experimental insecticide, RH-9999 to D. pulex was investigated using traditional 48 hr concentration-mortality estimates. Neemix and Azatin were equitoxic with LC50's of 0.68 and 0.57 ppm; RH-9999 was significantly less toxic with an LC50 of 13 ppm. A 10 d population growth study was conducted for Neemix and a Neemix formulation blank (Neemix devoid of the active ingredients) to determine whether the active ingredients of Neemix and/or components of the formulation were responsible for toxicity. D. pulex populations went to extinction after exposure to a Neemix concentration of 0.45 ppm azadirachtin (equivalent to the acute LC7). Neemix No Observable Effect Concentration (NOEC) and Lowest Observable Effect Concentration (LOEC) values for population growth were 0.045 and 0.15 ppm azadirachtin, respectively. The mean number of offspring per surviving female (Ro) declined in a concentration-dependent manner after exposure to Neemix with no offspring being produced after exposure to 0.45 ppm. Neemix NOEC and LOEC values for reproduction were 0.045 and 0.15 ppm, respectively. The formulation blank caused no mortality in the individuals used to start the population growth study but reduced reproduction and population growth accounting for 47% of the toxicity caused by Neemix at a concentration of 0.15 ppm. Thus, the formulation contributes substantially to the toxicity of Neemix but neem components are also toxic to D. pulex. Because the NOEC for population growth and reproduction were higher than the estimated environmental concentration of 0.035 ppm (a measure developed for forest pest mananagement), Neemix should pose little risk to populations of D. pulex.     

Exposure to trace elements of flamingos living in a biosphere reserve, the Camargue (France)

Recent research has shown that some adult flamingos Phoenicopterus roseus collected from the Camargue Biosphere Reserve had tissue metal concentrations considerably higher than the average for this species. As the range of these birds is large, the origin of the contamination was unknown. Blood and feather samples from nestling flamingos were therefore analysed for trace metals to determine the presence and origin of local contamination. A comparison of elemental concentration in the feathers of nestling and adult flamingos revealed higher concentrations of Cd, Cu, Pb and Se in adults, and higher concentrations of Zn in juveniles. This was attributed to increased exposure to atmospheric pollutants of adults, and either differences in Zn requirements and metabolism between adults and juveniles, or a local contamination of the juveniles' food supply by Zn. Concentrations of Zn in serum were also very elevated compared with human standards. Cd, Cu, Zn and Se concentrations were analysed in outer (O) and inner (I) barbs (i.e. barbs that are, respectively, exposed or not exposed to external deposits) of greater coverts of nestling flamingos. A comparison of elemental concentrations in these two feather components indicates a local atmospheric contamination by Cd, Cu and Pb.     

Distribution of metals and trace elements in adult and juvenile penguins from the Antarctic Peninsula area

The presence of metals in the Antarctic environment is principally a natural phenomenon caused by geochemical characteristics of the region, although some anthropogenic activities can increase these natural levels. Antarctic penguins present several of the characteristics of useful sentinels of pollution in Antarctica such as they are long-lived species situated at the top of food web. The concentrations of Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Cd, and Pb were determined by inductively coupled plasma–mass spectrometry in samples of liver, kidney, muscle, bone, feather, and stomach contents of gentoo, chinstrap, and Adélie penguin (12 adults, five juveniles) from carcasses of naturally dead individuals collected opportunistically in the Antarctic Peninsula area. The obtained results showed that accumulation and magnification of several elements can be occurring, so that Cd and Se reached levels potentially toxic in some specimens. The presence of human activities seems to be increasing the presence of toxic metals such as Mn, Cr, Ni, or Pb in penguins.     

Characterization and growth response of bacteria in soil following application of carbofuran.

Enhanced biodegradation of carbofuran (2, 3-dihydro-2, 2 dimethyl-7-benzofuranyl methyl carbamate) is an economically significant, but poorly understood, microbial phenomenon in soil. A series of experiments was conducted to examine short term changes in soil bacterial populations stimulated by carbofuran application at field rates. In the field experiment, commercially formulated carbofuran and butylate (S-ethyl diisobutyl carbamothioate) were applied at 5.6 kg ai ha-1 and 8.4 kg ai ha-1, respectively, on a soil (Putnam silt loam) exhibiting enhanced degradation of carbofuran. In laboratory studies, technical grade carbofuran (20 mg kg-1 soil) was applied to samples of the field soil. Bacterial populations were estimated using non-selective (tryptic soy agar) and selective media containing carbofuran or butylate. Largest population increases in pesticide-treated soil were observed between 7 and 15 days after treatment (DAT) compared to populations in non-treated soil. Significant increases (P less than 0.05) in total bacterial populations and presumed carbofuran-degraders due to carbofuran application were associated with increased populations of Pseudomonas spp. and Flavobacterium spp. Application of carbofuran appeared to provide a competitive advantage to these species over actinomycetes persisting beyond 20 DAT. Growth responses of bacteria to carbofuran in the Putnam soil were compared to those in a native prairie soil (Mexico silt loam), which exhibited a much slower rate of carbofuran degradation. Bacterial population response to carbofuran was measurable, but small and short-lived. Perpetuation of the enhanced degradation phenomenon may lie in a persistent pesticide-induced competitive advantage given to a very small segment of the microbial population. This advantage may not be detectable after 20 days using conventional plating techniques.     

Ancient manuring practices pollute arable soils at the St Kilda World Heritage Site, Scottish North Atlantic

The impact of ancient fertilization practices on the biogeochemistry of arable soils on the remote Scottish island of Hirta, St Kilda was investigated. The island was relatively unusual in that the inhabitants exploited seabird colonies for food, enabling high population densities to be sustained on a limited, and naturally poor, soil resource. A few other Scottish islands, the Faeroes and some Icelandic Islands, had similar cultural dependence on seabirds. Fertilization with human and animal waste streams (mainly peat ash and bird carcases) on Hirta over millennia has led to over-deepened, nutrient-rich soils (plaggen). This project set out to examine if this high rate of fertilization had adversely impacted the soil, and if so, to determine which waste streams were responsible. Arable soils were considerably elevated in Pb and Zn compared to non-arable soils. Using Pb isotope signatures and analysis of the waste streams, it was determined that this pollution came from peat and turf ash (Pb and Zn) and from bird carcases (Zn). This was also confirmed by ¹³C and ¹⁵N analysis of the profiles which showed that soil organic matter was highly enriched in marine-derived C and N compared to non-arable soils. The pollution of such a remote island may be typical of other ‘bird culture’ islands, and peat ash contamination of marginal arable soils at high latitudes may be widespread in terms of geographical area, but less intense at specific locations due to lower population densities than on Hirta.     

Lead impact on nutrition, energy reserves, respiration and stress protein (hsp 70) level in Porcellio scaber (Isopoda) populations differently preconditioned in their habitats

The impact of lead on food consumption, energy metabolism and the stress protein (hsp 70) level was investigated in the woodlouse Porcellio scaber (Isopoda), a common representative of the saprophagous soil macrofauna. To examine possible acclimation or tolerance to lead in woodlice from a contaminated habitat, animals of two populations, one deriving from a lead-contaminated artillery range and one from an uncontaminated control stand, were exposed to a series of lead concentrations under otherwise constant laboratory conditions for a maximum of 80 days. The applied lead concentrations (at a maximum 7945 mg/kg food dry wt) did not have any significant quantitative effect on the food consumption of the isopods, although the population pre-exposed in the artillery range showed a tendency toward a higher food uptake than the control population. After 80 days of exposure, both populations showed an equal trend toward increasing their respiration as lead concentrations, that they had been fed on, were increased. Accordingly, the glycogen content of the body, in both populations, was elevated with increasing lead concentrations in the food. This effect was more pronounced in the pre-exposed isopod population than in the one from the control stand. The non-pre-exposed isopods showed a general tendency toward a lower protein content of their bodies than the pre-exposed ones, although no effect of the lead on this parameter could be statistically proven. The ability of the artillery range isopods to synthesise stress proteins (hsp 70) in response to lead contamination decreased at much lower lead concentrations in their food than in the non-pre-exposed control population, even though the artillery range isopods seemed to be equally or even slightly better equipped with energy storage products. Even though the better nutrient status of these animals might refer to some lead tolerance of the pre-exposed population, the stress protein data suggest that a metal-resistant Porcellio population did not evolve in this lead-contaminated site.     

铀和铅对枯草杆菌毒性的研究

采用3种方法研究了铀和铅对枯草杆菌的毒性:(1)试纸法测抑菌圈的直径;(2)血球计数板测细菌菌数;(3)高倍显微镜下观察细菌形态和密度的变化.实验考察铀和铅的质量浓度为1～2 000 mg/L.结果表明:铀和铅对枯草杆菌的生长繁殖有显著影响;铀和铅对枯草杆菌的最大无作用剂量均小于1 mg/L;铀对枯草杆菌的致死质量浓度为500 mg/L,铅对枯草杆菌的致死质量浓度为 1 000 mg/L.同时,对以上3种方法进行了比较,确定了其各自的应用范围,为重金属对微生物毒性研究方法的选择提供了参考.