Mutualists and antagonists mediate frequency-dependent selection on floral display

Theory predicts that, with conflicting selection pressures mediated by mutualists and antagonists, alternative reproductive strategies can be maintained by negative frequency-dependent selection if it results in rare-morph advantage. We combined field experiments and surveys of natural populations to determine whether selection on floral display is frequency dependent in the self-incompatible herb Primula farinosa, which is polymorphic for inflorescence height and occurs in a short-scaped and a long-scaped morph. Among short-scaped plants, both pollination success, quantified as initiation of fruits and seeds, and seed predation were positively correlated with the relative frequency of the long-scaped morph. The relative strength of these effects and the direction of the resulting frequency-dependent selection on scape morph varied among years and populations. The results suggest that both mutualists and antagonists may mediate frequency-dependent selection and that frequency dependence may vary from positive to negative with rare-morph advantage, depending on the relative strength of these interactions.     

Characterizing source-sink dynamics with genetic parentage assignments

Source-sink dynamics have been suggested to characterize the population structure of many species, but the prevalence of source-sink systems in nature is uncertain because of inherent challenges in estimating migration rates among populations. Migration rates are often difficult to estimate directly with demographic methods, and indirect genetic methods are subject to a variety of assumptions that are difficult to meet or to apply to evolutionary timescales. Furthermore, such methods cannot be rigorously applied to high-gene-flow species. Here, we employ genetic parentage assignments in conjunction with demographic simulations to infer the level of immigration into a putative sink population. We use individual-based demographic models to estimate expected distributions of parent-offspring dyads under competing sink and closed-population models. By comparing the actual number of parent-offspring dyads (identified from multilocus genetic profiles) in a random sample of individuals taken from a population to expectations under these two contrasting demographic models, it is possible to estimate the rate of immigration and test hypotheses related to the role of immigration on population processes on an ecological timescale. The difference in the expected number of parent-offspring dyads between the two population models was greatest when immigration into the sink population was high, indicating that unlike traditional population genetic inference models, the highest degree of statistical power is achieved for the approach presented here when migration rates are high. We used the proposed genetic parentage approach to demonstrate that a threatened population of Marbled Murrelets (Braclhyrarmphus marmotus) appears to be supplemented by a low level of immigration (approximately 2-6% annually) from other populations.     

Partition of iodine (¹²⁹I and ¹²⁷I) isotopes in soils and marine sediments

Natural organic matter, such as humic and fulvic acids and humin, plays a key role in determining the fate and mobility of radioiodine in soil and sediments. The radioisotope ¹²⁹I is continuously produced and released from nuclear fuel reprocessing plants, and as a biophilic element, its environmental mobility is strongly linked to organic matter.Due to its long half-life (15.7 million years), ¹²⁹I builds up in the environment and can be traced since the beginning of the nuclear era in reservoirs such as soils and marine sediments. Nevertheless, partition of the isotope between the different types of organic matter in soil and sediment is rarely explored. Here we present a sequential extraction of ¹²⁹I and ¹²⁷I chemical forms encountered in a Danish soil, a soil reference material (IAEA-375), an anoxic marine sediment from Southern Norway and an oxic sediment from the Barents Sea. The different forms of iodine are related to water soluble, exchangeable, carbonates, oxides as well as iodine bound to humic acid, fulvic acid and to humin and minerals. This is the first study to identify ¹²⁹I in humic and fulvic acid and humin. The results show that 30-56% of the total ¹²⁷I and 42-60% of the total ¹²⁹I are associated with organic matter in soil and sediment samples. At a soil/sediment pH below 5.0-5.5, ¹²⁷I and ¹²⁹I in the organic fraction associate primarily with the humic acid while at soil/sediment pH > 6 ¹²⁹I was mostly found to be bound to fulvic acid. Anoxic conditions seem to increase the mobility and availability of iodine compared to oxic, while subaerial conditions (soils) reduces the availability of water soluble fraction compared to subaqueous (marine) conditions.     

Reduced European emissions of S and N--effects on air concentrations, deposition and soil water chemistry in Swedish forests

Changes in sulphur and nitrogen pollution in Swedish forests have been assessed in relation to European emission reductions, based on measurements in the Swedish Throughfall Monitoring Network. Measurements were analysed over 20 years with a focus on the 12-year period 1996 to 2008. Air concentrations of SO₂ and NO₂, have decreased. The SO₄-deposition has decreased in parallel with the European emission reductions. Soil water SO₄-concentrations have decreased at most sites but the pH, ANC and inorganic Al-concentrations indicated acidification recovery only at some of the sites. No changes in the bulk deposition of inorganic nitrogen could be demonstrated. Elevated NO₃-concentrations in the soil water occurred at irregular occasions at some southern sites. Despite considerable air pollution emission reductions in Europe, acidification recovery in Swedish forests soils is slow. Nitrogen deposition to Swedish forests continues at elevated levels that may lead to leaching of nitrate to surface waters.     

PCDD/F, PCB, PBDE, HBCD and chlorinated pesticides in a Swedish market basket from 2005--levels and dietary intake estimations

Based on consumption data statistics, food items from four regions in Sweden were sampled in a so-called market basket study. Food items from five food groups, i.e. fish, meat, dairy products, eggs and fat/oils, were analyzed for persistent organic pollutants (POPs) followed by per capita intake calculations. The highest levels of PCDD/F, PCB, PBDE, HBCD and chlorinated pesticides were found in the fish/fish products. The estimated market basket per capita intake of PCDD/F and dl-PCB was 0.7 pg WHO-TEQ kg bw⁻¹ d⁻¹ (TEFs from 1998). The intake of ∑PCB was estimated to 4.9 ng kg bw⁻¹ d⁻¹ and fish was found to be the major contributor with 64%. The intake of ∑PBDE was found to be 0.7 ng kg bw⁻¹ d⁻¹. Fish (38%) and dairy products (31%) were the largest contributors to the total PBDE intake. The intake of HBCD was estimated to 0.14 ng kg bw⁻¹ d⁻¹. HBCD mainly came from fish (65%), but also dairy products (24%) and meat (10%) contributed. Also regarding the chlorinated pesticides, fish was found to be the major contributor, with 51% of the ∑DDT coming from fish. The intake of ∑DDT, ∑HCH and HCB was 4.0, 1.0 and 1.1 ng kg bw⁻¹ d⁻¹, respectively. Most of the ∑HCH and HCB originate from dairy products (43% and 55%, respectively). This study shows that the levels, and intake, of different POPs from food of animal origin in the market basket of 2005 seem to have decreased since the market basket study in 1999.     

Effects of dry bulk density and particle size fraction on gas transport parameters in variably saturated landfill cover soil

Landfill sites are emerging in climate change scenarios as a significant source of greenhouse gases. The compacted final soil cover at landfill sites plays a vital role for the emission, fate and transport of landfill gases. This study investigated the effects of dry bulk density, ρ(b), and particle size fraction on the main soil-gas transport parameters - soil-gas diffusivity (D(p)/D(o), ratio of gas diffusion coefficients in soil and free air) and air permeability (k(a)) - under variably-saturated moisture conditions. Soil samples were prepared by three different compaction methods (Standard and Modified Proctor compaction, and hand compaction) with resulting ρ(b) values ranging from 1.40 to 2.10 g cm(-3). Results showed that D(p) and k(a) values for the '+gravel' fraction (<35 mm) became larger than for the '-gravel' fraction (<2mm) under variably-saturated conditions for a given soil-air content (ε), likely due to enhanced gas diffusion and advection through less tortuous, large-pore networks. The effect of dry bulk density on D(p) and k(a) was most pronounced for the '+gravel' fraction. Normalized ratios were introduced for all soil-gas parameters: (i) for gas diffusivity D(p)/D(f), the ratio of measured D(p) to D(p) in total porosity (f), (ii) for air permeability k(a)/k(a)(,pF4.1), the ratio of measured k(a) to k(a) at 1235 kPa matric potential (=pF 4.1), and (iii) for soil-air content, the ratio of soil-air content (ε) to total porosity (f) (air saturation). Based on the normalized parameters, predictive power-law models for D(p)(ε/f) and k(a)(ε/f) models were developed based on a single parameter (water blockage factor M for D(p) and P for k(a)). The water blockage factors, M and P, were found to be linearly correlated to ρ(b) values, and the effects of dry bulk density on D(p) and k(a) for both '+gravel' and '-gravel' fractions were well accounted for by the new models.     

Toxic effects of brominated flame retardants in man and in wildlife

Brominated flame retardants (BFRs) are ubiquitous industrial chemicals, and many of them are produced in large volumes. Due to this fact, several BFRs are found in quantifiable levels in wildlife, as well as in humans. However, we are still lacking information on the effects of BFR in wildlife and, especially, in man. This review summarises the biological effects of polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA) and derivates, hexabromocyclododecane (HBCD) and polybrominated biphenyls (PBBs), however excluding other aspects such as environmental levels. These BFR groups were selected because of a large volume production (PBDEs, TBBPA and derivates), and availability of some toxicity data in spite of much lower production volumes (HBCD and PBBs). In addition, the increase in levels of PBDEs in human (breast milk) and wildlife samples during later time made it especially interesting to include this BFR group. PBDES: The commercial PBDE products predominantly consist of so-called penta-, octa- and decabromodiphenyl ether products. Each product consists of a rather narrow range of congeners and is named after the dominating congener as regards the bromination pattern. Generally, the PentaBDEs seem to cause adverse effects at the comparably lowest dose, whereas much higher doses were needed for effects of the DecaBDEs. The critical effects of PentaBDEs are those on neurobehavioural development (from 0.6 mg/kg body weight) and, at somewhat higher dose, thyroid hormone levels in rats and mice, of OctaBDEs on fetal toxicity/teratogenicity in rats and rabbits (from 2 mg/kg body weight), and of DecaBDEs on thyroid, liver and kidney morphology in adult animals (from 80 mg/kg body weight). Carcinogenicity studies, only performed for DecaBDEs, show some effects at very high levels, and IARC (1990) evaluates DecaBDEs not classifiable as to its carcinogenicity to humans. TBBPA: The toxicity of TBBPA in the experimental in vivo studies is suggested to be low. In most reported studies, only doses in g/kg body weight were effective, but at least one study suggested renal effects at around 250 mg/kg body weight. Although difficult to include and interpret in a quantitative risk assessment, the in vitro effects on immunological and thyroid hormones, as well as binding to erythrocytes should be noted. Before a solid standpoint could be reached on TBBPA toxicity additional studies must be performed. This statement is even more valid regarding the TBBPA derivates, where there is an almost complete lack of toxicity data. HBCD: Also in the case of HBCD, relevant toxicity studies are lacking. Based on the present animal studies, a critical effect is seen in the liver and on thyroid hormones (LOAEL 100 mg/kg body weight/day). However, in a recent short paper behavioural effects in mice pups were observed already at 0.9 mg/kg body weight, and behavioural effects may be a sensitive endpoint for HBCD, as well as for other BFRs. PBBS: Due to the Michigan accident in 1973-1974, many toxicity studies on PBBs are available. The critical experimental effects are those on reproduction and carcinogenicity, and a NOAEL of 0.15 mg/kg body weight/day could be suggested based on the cancer effects. In man no unequivocal effects have been observed, although in some studies neurological and musculoskeletal symptoms were suggested. Based on the carcinogenic effects in animals, a human TDI of 0.15 microg/kg body weight has been presented.To conclude, the toxicity data are almost entirely based on experimental models. There are differences among the BFR groups, as well as within these groups, both regarding type of toxic effect and at what dose it appears. As BFRs will continue to appear both in industrial applications and, even if the production has ceased, in our environment, there is a continued need for effects studies on BFRs.     

AhR agonist and genotoxicant bioavailability in a PAH-contaminated soil undergoing biological treatment

Background, aim, and scope  Degradation of the 16 US EPA priority PAHs in soil subjected to bioremediation is often achieved. However, the PAH loss is not always followed by a reduction in soil toxicity. For instance, bioanalytical testing of such soil using the chemical-activated luciferase gene expression (CALUX) assay, measuring the combined effect of all Ah receptor (AhR) activating compounds, occasionally indicates that the loss of PAHs does not correlate with the loss of Ah receptor-active compounds in the soil. In addition, standard PAH analysis does not address the issue of total toxicant bioavailability in bioremediated soil. Materials and methods  To address these questions, we have used the CALUX AhR agonist bioassay and the Comet genotoxicity bioassay with RTL-W1 cells to evaluate the toxic potential of different extracts from a PAH-contaminated soil undergoing large-scale bioremediation. The extracts were also chemically analyzed for PAH16 and PCDD/PCDF. Soil sampled on five occasions between day 0 and day 274 of biological treatment was shaken with n-butanol with vortex mixing at room temperature to determine the bioavailable fraction of contaminants. To establish total concentrations, parts of the same samples were extracted using an accelerated solvent extractor (ASE) with toluene at 100°C. The extracts were tested as inducers of AhR-dependent luciferase activity in the CALUX assay and for DNA breakage potential in the Comet bioassay. Results  The chemical analysis of the toluene extracts indicated slow degradation rates and the CALUX assay indicated high levels of AhR agonists in the same extracts. Compared to day 0, the bioavailable fractions showed no decrease in AhR agonist activity during the treatment but rather an up-going trend, which was supported by increasing levels of PAHs and an increased effect in the Comet bioassay after 274 days. The bio-TEQs calculated using the CALUX assay were higher than the TEQs calculated from chemical analysis in both extracts, indicating that there are additional toxic PAHs in both extracts that are not included in the chemically derived TEQ. Discussion  The response in the CALUX and the Comet bioassays as well as the chemical analysis indicate that the soil might be more toxic to organisms living in soil after 274 days of treatment than in the untreated soil, due to the release of previously sorbed PAHs and possibly also metabolic formation of novel toxicants. Conclusions  Our results put focus on the issue of slow degradation rates and bioavailability of PAHs during large-scale bioremediation treatments. The release of sorbed PAHs at the investigated PAH-contaminated site seemed to be faster than the degradation rate, which demonstrates the importance of considering the bioavailable fraction of contaminants during a bioremediation process. Recommendations and perspectives  It has to be ensured that soft remediation methods like biodegradation or the natural remediation approach do not result in the mobilization of toxic compounds including more mobile degradation products. For PAH-contaminated sites this cannot be assured merely by monitoring the 16 target PAHs. The combined use of a battery of biotests for different types of PAH effects such as the CALUX and the Comet assay together with bioavailability extraction methods may be a useful screening tool of bioremediation processes of PAH-contaminated soil and contribute to a more accurate risk assessment. If the bioremediation causes a release of bound PAHs that are left undegraded in an easily extracted fraction, the soil may be more toxic to organisms living in the soil as a result of the treatment. A prolonged treatment time may be one way to reduce the risk of remaining mobile PAHs. In critical cases, the remediation concept might have to be changed to ex situ remediation methods.