Concentrations of dioxin-like PCB congeners in unweathered Aroclors by HRGC/HRMS using EPA Method 1668A

We have determined the congener compositions of nine commercial Aroclor products of polychlorinated biphenyls (PCBs) to the sub-part-per-million level using high-resolution gas chromatography combined with high-resolution mass spectrometry according to US Environmental Protection Agency (EPA) Method 1668A. These Aroclor composition data should allow improved characterization and risk assessment of PCB contamination at hazardous waste sites, particularly for dioxin-like PCB congeners. By combining the data on the concentrations of each dioxin-like congener with its World Health Organization toxicity equivalency factor, we have established dioxin toxic equivalent concentrations for each pure Aroclor product.     

Factors controlling lead bioavailability in the Butte mining district,Montana, USA

Microprobe analyses of 38 soil and 5 mine-waste samples from Butte, Montana, demonstrated that the samples contain predominantly sulphide/sulphate and oxide/phosphates of lead (Pb)-bearing phases associated with mine waste. The sulphide/sulphate assemblage consists primarily of galena altering to anglesite and plumbojarosite, with secondary jarosite precipitating and rinding the Pb-bearing minerals. In addition, galena was encapsulated within pyrite or quartz grains. The oxide/phosphate assemblage consists of pH-neutral soils in which a plausible paragenetic sequence of PbO to Pb phosphates, PbMnO, or PbFeO is proposed, dependent on the activity of P, Mn, Fe, and Cl in the soil. In addition, Pb-bearing grains are occasionally armoured by the presence of a 1- to 3-(m rind of authigenic silicate. The low solubility of the Pb-bearing minerals resulting from encapsulation in non-Pb-bearing reaction rinds may provide an explanation for the limited Pb bioavailability observed when Butte soils were fed to rats (Freemanet al., 1992). Further evidence of the lack of absorption of lead from these soils is provided by the results of a blood-Pb study indicating very low blood-Pb levels in Butte children. The lower bioavailability of Pb from mining sites, compared to smelting and urban environments, is also due to kinetic limitations that control dissolution rates of Pb-bearing solids relative to the residence time of soil in the gastrointestinal (Gl) tract. When the test soil was fed to New Zealand White rabbits, only 9% of the total Pb was solubilised in the stomach, and therefore available for absorption. Anin vitro assay, developed to estimate maximum available Pb from soil, demonstrates that ingestion of mine-waste-bearing soil results in limited Pb dissolution, and produces results similar to thein vivo testing.     

"Cryptic" direct benefits of mate choice: choosy females experience reduced predation risk while in precopula

Despite the central role that female mate choice plays in the production of biological diversity, controversy remains concerning its evolution and maintenance. This is particularly true in systems where females are choosy but do not receive obvious direct benefits such as nuptial gifts that increase a female's survival and fecundity. In the absence of such direct benefits, indirect benefits (i.e., the production of superior offspring) are often invoked to explain the evolution of mate choice. However, females may receive less obvious, or "cryptic," direct benefits, particularly in species with prolonged pre-mating interactions (e.g., precopulatory mate guarding). We assessed the “cryptic” direct benefits of female choice for large male size in two species of freshwater amphipods that do not receive obvious direct benefits. Females paired with large males experienced decreased predation from fish. However, we found that the size of a female’s mate did not affect her predation risk against predatory dragonflies or the harassment she received by single males while paired. Our results demonstrate that even when females receive no traditional direct benefits, female choice for large male size can still provide important direct benefits. Such “cryptic” direct benefits may be common, especially in species with prolonged mating interactions, and are likely important for fully understanding the evolution of mate choice.     

Application Of Artificial Neural Network Models To Analyse The Relationships Between Gammarus pulex L. (Crustacea, Amphipoda) And River Characteristics

This study aimed at analysing the relationship between river characteristics and abundance of Gammarus pulex. To this end, four methods which can identify the relative contribution and/or the contribution profile of the input variables in neural networks describing the habitat preferences of this species were compared: (i) the ‘PaD‘ (‘Partial Derivatives‘) method consists of a calculation of the partial derivatives of the output in relation to the input variables; (ii) the ‘Weights‘method is a computation using the connection weights of the backpropagation Artificial Neural Networks; (iii) the ‘Perturb‘method analyses the effect of a perturbation of the input variables on the output variable; (iv) the ‘Profile‘ method is a successive variation of one input variable while the others are kept constant at a fixed set of values. The dataset consisted of 179 samples, collected over a three-year period in the Zwalm river basin in Flanders, Belgium. Twenty-four environmental variables as well as the log-transformed abundance of Gammarus pulex were used in this study. The different contribution methods gave similar results concerning the order of importance of the input variables. Moreover, the stability of the methods was confirmed by gradually removing variables. Only in a limited number of cases a shift in the relative importance of the remaining input variables could be observed. Nevertheless, differences in sensitivity and stability of the methods were detected, probably as a result of the different calculation procedures. In this respect, the ‘PaD‘method made a more severe discrimination between minor and major contributing environmental variables in comparison to the ‘Weights‘, ‘Profile‘ and ‘Perturb‘ methods. From an ecological point of view, the input variables ‘Ammonium‘ and to a smaller extent ‘COD‘, were selected by these methods as dominant river characteristics for the prediction of the abundance of Gammarus pulex in this study area.     

Transport of brine shrimps via the digestive system of migratory waders: dispersal probabilities depend on diet and season

Waterbirds are known to disperse invertebrate propagules that survive gut passage, but there is very little information about how the probability of dispersal changes at different times of the annual cycle when birds move in different directions, or how it is affected by changes in diet. We studied internal transport of brine shrimp Artemia cysts by migratory waders in the Odiel saltworks in south-west Spain. Viable cysts of parthenogenetic Artemia were abundant in the faeces and regurgitated pellets of redshank Tringa totanus, pellets of spotted redshank T. erythropus, and faeces of black-tailed godwit Limosa limosa during spring and/or autumn migrations in 2001–2002, but were not recorded during winter. Godwits did not produce pellets, and spotted redshank faeces were not sampled. Significant correlations between the number of cysts in a pellet or faecal sample and the proportion of that sample constituted by Artemia adults suggested that most cysts were ingested while in the ovisacs of gravid females. The proportion of cysts destroyed during digestion increased when accompanied by harder food items or grit, and when fewer cysts were ingested. The median number of intact cysts was higher in redshank faeces than in their pellets, but cysts extracted from pellets were more likely to hatch. A higher proportion of redshank pellets contained Artemia cysts in spring than in autumn, but more redshank migrated through the area in autumn. Significantly fewer cysts were recorded in redshank pellets in winter than in spring or autumn. Our results confirm that there is potential for long-distance dispersal of Artemia cysts via waders during both northwards (spring) and southwards (autumn) migrations.     

Spatial ecology and residency patterns of adult great barracuda (<Emphasis Type="Italic">Sphyraena barracuda</Emphasis>) in coastal waters of The Bahamas

Great barracuda (Sphyraena barracuda) were implanted with acoustic telemetry transmitters (n = 42) and monitored within a stationary acoustic receiver array (n = 53 receivers) in The Bahamas to examine residency, seasonal movements, and habitat use. Barracuda were monitored for up to 980 days and remained within the array area ~33% (median value) of the time. Most tagged barracuda were transient and would often disappear from the array for months at a time, particularly in the summer where they were usually last detected on receivers located in deeper shelf habitats, and then return at other times in the year. Habitat use across the footprint of the array differed, with most detections occurring in coastal areas and comparatively fewer in deeper mosaic or shelf habitats. Linear home range estimates revealed that some barracuda moved >12 km within a single day and are capable of migrating >100 km to other islands in the Bahamian Archipelago. Our results provide some of the first telemetry data for this apex marine predatory fish and the first reliable information on the residency and localized seasonal movements of adult great barracuda in the coastal waters of the Western Atlantic.     

Livestock mortality in pastoralist herds in Ethiopia and implications for drought response

Participatory epidemiology methods were employed retrospectively in three pastoralist regions of Ethiopia to estimate the specific causes of excess livestock mortality during drought. The results showed that starvation/dehydration accounted for between 61.5 and 100 per cent of excess livestock mortality during drought, whereas disease‐related mortality accounted for between 0 and 28.1 per cent of excess mortality. Field observations indicate that, in livestock, disease risks and mortality increase in the immediate post‐drought period, during rain. The design of livelihoods‐based drought response programmes should include protection of core livestock assets, and it should take account of the specific causes of excess livestock mortality during drought and immediately afterwards. This study shows that, when comparing livestock feed supplementation and veterinary support, relatively more aid should be directed at the former if the objective is to protect core livestock during drought. Veterinary support should consider disease‐related mortality in the immediate post‐drought period, and tailor inputs accordingly.