Imposex and decline in reproductive output in marine gastropods have been linked to tributyltin (TBT) exposure. This study describes Chesapeake Bay, USA, veined rapa whelk Rapana venosa imposex incidence and sex ratios from 1998 to 2009. Tissue TBT concentrations (ng g?1) were examined with respect to whelk sex, size, and water temperature at the time of collection, and also to egg case size, hatching success, and veliger diameter. Imposex incidence declined and population sex ratios moved closer to parity from 1998 to 2009. Observed TBT concentrations (ng g?1) were higher in James River than in Ocean View whelks with higher TBT concentrations observed in males than in females. Exponential declines in TBT concentrations from female-specific first to last clutches within a reproductive season were observed, indicating that whelks depurate TBT through egg case deposition. Egg capsule hatching success and veliger size were similar for female and imposex whelks. The R. venosa imposex levels observed in Chesapeake Bay apparently do not affect the production, release, or viability of larvae. 相似文献
The field of fisheries research commonly uses classical statistical classification methods to estimate the proportion of fish that return to natal spawning grounds to spawn. With the advent of otolith microchemical analysis, researchers are able to extract information from fish ear stones (otoliths) about the chemical composition of water in which fish have spent distinct periods of their lives. Here we present a method of analysis set in the Bayesian statistical paradigm which enables explicit incorporation of habitat information into the analysis. The ecological system is seen as arising from a mixture of disparate fish populations and information from the biological relationships inherent in otolith formation is exploited through the hierarchical model structure. We present the model and motivation, demonstrate the validity of the model through simulation studies, and conclude with an analysis of a data set from Lake Erie. 相似文献
Analyses of the pattern of associations, social interactions, coalitions, and aggression among chacma baboons (Papio hamadryas ursinus) in the Okavango Delta of Botswana over a 16-year period indicate that adult females form close, equitable, supportive, and
enduring social relationships. They show strong and stable preferences for close kin, particularly their own mothers and daughters.
Females also form strong attachments to unrelated females who are close to their own age and who are likely to be paternal
half-sisters. Although absolute rates of aggression among kin are as high as rates of aggression among nonkin, females are
more tolerant of close relatives than they are of others with whom they have comparable amounts of contact. These findings
complement previous work which indicates that the strength of social bonds enhances the fitness of females in this population
and support findings about the structure and function of social bonds in other primate groups. 相似文献
Mountain biking is an increasingly popular, but sometimes controversial, activity in protected areas. Limited research on its impacts, including studies comparing biking with hiking, contributes to the challenges for mangers in assessing its appropriateness. The impacts of mountain bike riding off trail were compared to those of hiking on subalpine grassland in Australia using a modification of a common trampling experimental methodology. Vegetation and soil parameters were measured immediately and two weeks after different intensities of mountain biking (none, 25, 75, 200 and 500 passes across slope, 200 pass up and down slope) and hiking (200 and 500 passes across slope). There were reductions in vegetation height, cover and species richness, as well as changes in species composition and increases in litter and soil compaction with riding. Riding up and down a moderate slope had a greater impact than riding across the slope. Hiking also affected vegetation height, cover and composition. Mountain biking caused more damage than hiking but only at high use (500 passes). Further research including other ecosystems, topography, styles of riding, and weather conditions are required, but under the conditions tested here, hiking and mountain biking appear to be similar in their environmental impacts. 相似文献
The optimal design of multicontaminant industrial water networks according to several objectives is carried out in this paper. The general formulation of the water allocation problem (WAP) is given as a set of nonlinear equations with binary variables representing the presence of interconnections in the network. For optimization purposes, three antagonist objectives are considered: F(1), the freshwater flow-rate at the network entrance, F(2), the water flow-rate at inlet of regeneration units, and F(3), the number of interconnections in the network. The multiobjective problem is solved via a lexicographic strategy, where a mixed-integer nonlinear programming (MINLP) procedure is used at each step. The approach is illustrated by a numerical example taken from the literature involving five processes, one regeneration unit and three contaminants. The set of potential network solutions is provided in the form of a Pareto front. Finally, the strategy for choosing the best network solution among those given by Pareto fronts is presented. This Multiple Criteria Decision Making (MCDM) problem is tackled by means of two approaches: a classical TOPSIS analysis is first implemented and then an innovative strategy based on the global equivalent cost (GEC) in freshwater that turns out to be more efficient for choosing a good network according to a practical point of view. 相似文献
Nutrient recycling by animals is a potentially important biogeochemical process in both terrestrial and aquatic ecosystems. Stoichiometric traits of individual species may result in some taxa playing disproportionately important roles in the recycling of nutrients relative to their biomass, acting as keystone nutrient recyclers. We examined factors controlling the relative contribution of 12 Neotropical fish species to nutrient recycling in four streams spanning a range of phosphorus (P) levels. In high-P conditions (135 microg/L soluble reactive phosphorus, SRP), most species fed on P-enriched diets and P excretion rates were high across species. In low-P conditions (3 microg/L SRP), aquatic food resources were depleted in P, and species with higher body P content showed low rates of P recycling. However, fishes that were subsidized by terrestrial inputs were decoupled from aquatic P availability and therefore excreted P at disproportionately high rates. One of these species, Astyanax aeneus (Characidae), represented 12% of the total population and 18% of the total biomass of the fish assemblage in our focal low-P study stream but had P excretion rates > 10-fold higher than other abundant fishes. As a result, we estimated that P excretion by A. aeneus accounted for 90% of the P recycled by this fish assemblage and also supplied approximately 90% of the stream P demand in this P-limited ecosystem. Nitrogen excretion rates showed little variation among species, and the contribution of a given species to ecosystem N recycling was largely dependent upon the total biomass of that species. Because of the high variability in P excretion rates among fish species, ecosystem-level P recycling could be particularly sensitive to changes in fish community structure in P-limited systems. 相似文献
The extractability of Cd, Pb, and Zn was investigated in contaminated agricultural topsoils located in an area highly affected
by the past atmospheric emissions of two smelters in northern France in order to assess their mobility and human bioaccessibility.
The determination of Cd, Pb, and Zn bioaccessibility (Unified Barge Method, in vitro test) was made to evaluate the absolute
trace element (TE) bioavailability. The results highlighted differences in bioaccessibility between Cd, Pb, and Zn (Cd > Pb > Zn).
The mean values of the bioaccessible fractions of Cd, Pb, and Zn during the gastric phase were 82, 55, and 33%, respectively,
of the pseudototal concentrations, whereas during the gastrointestinal phase, the bioaccessible fractions of metals decreased
to 45, 20, and 10%, respectively. Stepwise multiple regression analysis showed that human bioaccessibility was affected by
various physicochemical parameters (i.e., sand, carbonates, organic matter, assimilated P, free Al oxides, and pseudototal
Fe contents). Sequential extractions were performed as an indication of the TE availability in these soils. Cadmium occurred
in the more available fractions, Pb was mostly present as bound by oxides, and a significant contribution to the pseudototal
Zn concentration was defined as the unavailable residual form related to the crystalline structures of minerals. The concepts
of bioavailability and bioaccessibility are important for quantifying the risks associated with exposure to environmental
pollutants and providing more realistic information for human health. 相似文献
Falls in older Australians are a significant public health issue with one in three older people falling one or more times each year.
Method
Many fall prevention randomized controlled trials have been conducted in Australia as well as across the world.
Results
The findings of these studies now constitute a substantial evidence base that can provide direction for health and lifestyle interventions for preventing falls in older people. This research evidence has contributed to health policy in Australia to some extent, but is yet to be widely implemented into practice. This opinion piece overviews previous policy initiatives and describes a new Partnership research program funded by the Australian National Health and Medical Research Council (NHMRC), which seeks to further influence health policy and address the ongoing research-practice gap. 相似文献
Environmental Chemistry Letters - Silicon (Si) is the most abundant element on the earth’s surface after oxygen. Si can be found in minerals, electronic chips, cosmetic... 相似文献
Oil contamination has become a primary environmental concern due to increased exploration, production, and use. When oil enters the soil, it may attach or adsorb to soil particles and stay in the soil for an extended period, contaminating the soil and surrounding areas. Nanoparticles have been widely used for the treatment of organic pollutants in the soil. Surfactant foam has effectively been employed to remediate various soil contaminants or recover oil compounds. In this research, a mixture of biosurfactant foam/nanoparticle was utilized for remediation of oil-contaminated soil. The results demonstrated that the biosurfactant/nanoparticle mixture and nitrogen gas formed high-quality and stable foams. The foam stability depended on the foam quality, biosurfactant concentration, and nanoparticle dosage. The pressure gradient change in the soil column relied on the flowrate (N2 gas + surfactant/nanoparticle mixture), foam quality, and biosurfactant concentration. The optimal conditions to obtain good quality and stable foams and high oil removal efficiency involved 1 vol% rhamnolipid, 1 wt% nanoparticle, and 1 mL/min flowrate. Biosurfactant foam/nanoparticle mixture was effectively used to remediate oil-contaminated soil, whereas the highest treatment efficiency was 67%, 59%, and 52% for rhamnolipid biosurfactant foam/nanoparticle, rhamnolipid biosurfactant/nanoparticle, and only rhamnolipid biosurfactant, respectively. The oil removal productivity decreased with the increase of flowrate due to the shorter contact time between the foam mixture and oil droplets. The breakthrough curves of oil pollutants in the soil column also suggested that the foam mixture’s maximum oil treatment efficiency was higher than biosurfactant/nanoparticle suspension and only biosurfactant.