Climate change threatens polar bear populations: a stochastic demographic analysis

The polar bear (Ursus maritimus) depends on sea ice for feeding, breeding, and movement. Significant reductions in Arctic sea ice are forecast to continue because of climate warming. We evaluated the impacts of climate change on polar bears in the southern Beaufort Sea by means of a demographic analysis, combining deterministic, stochastic, environment-dependent matrix population models with forecasts of future sea ice conditions from IPCC general circulation models (GCMs). The matrix population models classified individuals by age and breeding status; mothers and dependent cubs were treated as units. Parameter estimates were obtained from a capture-recapture study conducted from 2001 to 2006. Candidate statistical models allowed vital rates to vary with time and as functions of a sea ice covariate. Model averaging was used to produce the vital rate estimates, and a parametric bootstrap procedure was used to quantify model selection and parameter estimation uncertainty. Deterministic models projected population growth in years with more extensive ice coverage (2001-2003) and population decline in years with less ice coverage (2004-2005). LTRE (life table response experiment) analysis showed that the reduction in lambda in years with low sea ice was due primarily to reduced adult female survival, and secondarily to reduced breeding. A stochastic model with two environmental states, good and poor sea ice conditions, projected a declining stochastic growth rate, log lambdas, as the frequency of poor ice years increased. The observed frequency of poor ice years since 1979 would imply log lambdas approximately - 0.01, which agrees with available (albeit crude) observations of population size. The stochastic model was linked to a set of 10 GCMs compiled by the IPCC; the models were chosen for their ability to reproduce historical observations of sea ice and were forced with "business as usual" (A1B) greenhouse gas emissions. The resulting stochastic population projections showed drastic declines in the polar bear population by the end of the 21st century. These projections were instrumental in the decision to list the polar bear as a threatened species under the U.S. Endangered Species Act.     

Signal recognition by frogs in the presence of temporally fluctuating chorus-shaped noise

The background noise generated in large social aggregations of calling individuals is a potent source of auditory masking for animals that communicate acoustically. Despite similarities with the so-called "cocktail-party problem" in humans, few studies have explicitly investigated how non-human animals solve the perceptual task of separating biologically relevant acoustic signals from ambient background noise. Under certain conditions, humans experience a release from auditory masking when speech is presented in speech-like masking noise that fluctuates in amplitude. We tested the hypothesis that females of Cope's gray treefrog (Hyla chrysoscelis) experience masking release in artificial chorus noise that fluctuates in level at modulations rates characteristic of those present in ambient chorus noise. We estimated thresholds for recognizing conspecific advertisement calls (pulse rate=40-50 pulses/s) in the presence of unmodulated and sinusoidally amplitude modulated (SAM) chorus-shaped masking noise. We tested two rates of modulation (5 Hz and 45 Hz) because the sounds of frog choruses are modulated at low rates (e.g., less than 5-10 Hz), and because those of species with pulsatile signals are additionally modulated at higher rates typical of the pulse rate of calls (e.g., between 15-50 Hz). Recognition thresholds were similar in the unmodulated and 5-Hz SAM conditions, and 12 dB higher in the 45-Hz SAM condition. These results did not support the hypothesis that female gray treefrogs experience masking release in temporally fluctuating chorus-shaped noise. We discuss our results in terms of modulation masking, and hypothesize that natural amplitude fluctuations in ambient chorus noise may impair mating call perception.     

Monitoring of Bt-Maize pollen exposure in the vicinity of the nature reserve Ruhlsdorfer Bruch in northeast Germany 2007 to 2008

Background, aim, and scope Basically, technological innovations are associated with benefits and risks. This is also true for the introduction of genetically modified organisms (GMO) into agriculture. In Germany, precautionary regulations currently demand isolation distances (i.?e. buffer zones) for the cultivation of genetically modified maize (Bt-maize) in the vicinity of conventional (150?m) and organic maize fields (300?m). The Bt-toxin may harm non-target organisms (NTO) such as Lepidoptera. Despite this, corresponding regulations for the protection of nature reserves are lacking to date. Conventional and Bt-maize have been grown in the vicinity of the Flora-Fauna-Habitat (FFH) Ruhlsdorfer Bruch in Brandenburg, Germany. The aim of this study was to investigate whether exposure of maize pollen from surrounding Bt-maize fields to NTOs in the nature protection area could be excluded or not. Two types of exposure were investigated: Firstly, whether maize pollen was dispersed by wind into the nature reserve area exposing resident NTOs. Secondly, foraging NTOs from the nature reserve are exposed by roaming the surrounding fields and collecting maize pollen. In order to fulfil the precautionary principle defined by law, the study should help to determine appropriate isolation distances for the cultivation of Bt-maize with regard to sustainable protection of NTOs in the FFH Ruhlsdorfer Bruch. In 2007, the local authorities issued an isolation distance between Bt-maize fields and nature reserves of 100?m and in 2008, this became 250?m in the northern and 500?m in the westerly direction, respectively. Materials and methods Standardised methods for biological and technical pollen sampling issued by the Association of German Engineers (VDI 4330 Part 3, 2007 and VDI 4330 Part 4, 2006) were applied providing a quality controlled and methodologically harmonised database which does not only serve the needs to be fulfilled by the present case-specific monitoring study but can also be used as a reference database for further investigations. Maize pollen exposure was measured within the FFH Ruhlsdorfer Bruch and its immediate vicinity in July and August 2007 and 2008. In 2007, the sampling was performed at three sites using 12 technical samplers (Sigma-2/PMF) placed at five measuring points at distances from 5?m to 120?m from the maize field edges. Additionally, for biological pollen sampling six bee colonies were situated at these three sites (two colonies at each site). The technical sampler Sigma-2/PMF enables point sampling which is primarily influenced by wind and topography providing information on effective maize pollen input (flow and deposition) at the measuring sites. Honey-bees roaming in the surrounding area with typical foraging distances of several kilometres may act as planar collectors. They may serve as indicators for the exposure to pollen-collecting NTOs. Furthermore, biological sampling is more selective due to the organism’s preferences, whereas the technical sampling is neutral. Hence, both the technical and the biological sampling complement each other in their scope of application. The pollen samples of both matrices were analysed microscopically and the maize pollen loads were quantified. Pollen-DNA was analysed by means of the quantitative PCR-method (qPCR) identifying conventional and Bt-maize pollen by two independent laboratories. In 2008, the monitoring was repeated with additional sites. Eighteen technical samplers were exposed at five sites with eight measuring points at distances from 5?m to 250?m from the maize field edges. Two honey-bee colonies for biological sampling were placed at one site for control purposes. PCR-analyses were performed to measure the amounts of Bt-maize pollen in the samples. Results The results of pollen monitoring at the Ruhlsdorfer Bruch revealed maize pollen exposure for all monitoring sites in both surveys. In 2007, up to 1.75 million maize pollen/m² were deposited at sites closest to the maize field. At 120?m from field edge in the middle of the FFH-reserve, 99,000 maize pollen/m² were detected. In 2008, similar results were found, at distances up to 250?m from the field edges deposition of 164,000 maize pollen/m² was detected. Data on maize pollen deposition show a clear distance relationship and are in accordance with results of further comprehensive surveys based on the same methodology (Hofmann 2007). The results of the microscopic analysis of the pollen pellets demonstrated that bees collected maize pollen at all sites, in 2007 and 2008. Although maize pollen is not the main food source (2007:0.1–0.3?%; 2008:2–3?%) the collection efficiency of the bee colonies resulted in high amounts of sampled maize pollen with 4 to 11 million per site in 2007 and up to 467 million in 2008. Molecular-biological analysis of maize pollen DNA by qPCR demonstrated that transgenic Bt-MON810 DNA was present in all technical and biological samples, corroborated by two independent laboratories. In 2007, the GMO-content in the samples ranged up to 44?% in the bioaerosols and 49?% in the pollen pellets. In 2008, GMO-proportions of up to 18?% were detected. Discussion The results of this study provide evidence that NTOs in the Ruhlsdorfer Bruch were exposed to Bt-maize pollen under the cultivation conditions in 2007 with a buffer zone of 100?m. The GMO-content reached up to 48?%. The results of the monitoring in 2008 confirmed these findings. Even though the exposure could be reduced by increasing the isolation distances to 250?m and 500?m respectively, the results still show percentages of up to 18?% Bt-MON810 in the pollen samples. The results on maize pollen deposition at the Ruhlsdorfer Bruch in 2007 and 2008 correspond to the results of an investigation which was conducted over several years applying the same standardised method, but covering a wider range of distances. The correlation between maize pollen deposition (n/m²) and distance to the source field (m) fitted best to a power function of the type y = 1.2086 · 10⁶ · x ^–0.548. Despite the same trend, the pollen deposition in the Ruhlsdorfer Bruch revealed above-average findings. Also the analysis of the pollen pellets collected by the bees showed an exposure in 2007 with values for the GMO-content of up to 49?%. For both methods, the exposure decreased in 2008 due to the greater buffer zones up to 500?m. Whereas the GMO-content for the biological sampling were reduced to values below 10?%, the values for the technical sampling were still higher indicating that greater buffer zones would be necessary for safety reasons under the precautionary principle. Conclusions The results of this investigation proved that maize pollen were dispersed by wind to distances farther than 250?m from field edge leading to maize pollen exposure in the centre of the nature reserve. The results also demonstrated that foraging NTOs living in the nature reserve were exposed to maize pollen from surrounding fields. Considering the cultivation of Bt-maize MON810, the assumption of the Environmental Risk Assessment (ERA) that there will be no relevant exposure beyond the Bt-maize fields, cannot be confirmed. Considering the results of this and related studies and with respect to the precautionary principle, one can state that buffer zones between Bt-maize fields and protected areas are an effective measure to minimise the exposure of Bt-maize pollen to NTOs and, thus, to prevent from adverse effects. Recommendations and perspectives Because of still insufficient ecotoxicological data for the risk assessment of Bt-maize MON810 considering butterflies and other protected NTOs, protection standards assuring the precautionary principle have to be implemented to avoid Bt-maize pollen exposure to NTOs. This applies for the case Ruhlsdorfer Bruch and for nature reserve areas in general. In order to exclude risks to protected NTOs occurring in nature reserves, sufficient buffer zones for Bt-maize cultivation should be considered. The statistical analysis revealed that distances of more than 500?m are necessary to decisively reduce exposure to foraging insects. In fact, distances of more than 1,000?m are necessary to prevent maize pollen deposition from values above 100,000 pollen/m² with a certainty of 90?%. An adequate risk assessment can only be attained if based on field measurements accounting for the high variation of pollen deposition due to local environmental site conditions and field management. The monitoring should be based on standardised methods. It should include locations with the highest expected deposition rates, the boundaries of the protected areas and sites of interest within those boundaries, e.?g., specific habitats of sensitive species.     

Management von schadstoffbelasteten Feinsedimenten in Bundeswasserstraßen

The Federal Institute of Hydrology has developed operating strategies in order to deal with dredged material within the scope of the Waterways and Shipping Administration. Sediments will be assessed based on certain quality parameters. The potential environmental impact at the source and relocation areas has to be evaluated in respect to ecological and economical issues. A coordinated sediment management plan for the Rhine River was commissioned. The most important contaminated sedimentation areas were identified, and special sedimentation areas were classified based on ecological impact or even risk. Proposals for economical and ecological strategies are discussed. Further developments for operational instructions dealing with sediments and dredged material in federal waterways are still being processed. The objectives of the river basin commissions as well as those of the stakeholders have to be met in an appropriate manner. In the framework of the analysis and impact of climate change on both sediment quantity and quality for optimizing sediment management, one or more dimensional hydraulic models will be applied. This will help gain a better insight into the understanding of contaminant transport in freshwater bodies.     

Toxizität und Risk Assessment fluvialer Sedimente und Schwebstoffe: Eine kurze Übersicht bisheriger und neuerer Entwicklungen

Background In recent years, sediments have become a central topic of scientific and public discussion as an important factor for determining water quality. While the quality of surface waters in Germany has significantly improved during the past years, highly contaminated sediments still create a considerable threat to the quality of several European catchment areas. Main features Here, we summarize different concepts and methods for the assessment of sediment quality and report on some novel integrative test methods for assessing sediment toxicity including contaminant re-mobilization during simulated re-suspension events. Results and discussion Currently, different approaches for assessment of sediment pollution exist. While instrumental chemical analyses are not suitable to accurately describe sediment toxicity, combinations of biological and chemical test procedures and integrated approaches, for example weight-of-evidence studies and effect-directed analysis (EDA), have the potential to identify key contaminants. Inter-disciplinary studies combining hydrodynamic and toxicological aspects coupled to real exposure of aquatic organisms to contaminants are currently being developed. Conclusions Monitoring and assessment of sediment quality are of increasing importance, not only for national legislation but also for the implementation of the European Water Framework Directive (WFD). Integrated approaches for the determination of sediment stability play a key role in the appropriate sediment-monitoring strategies.     

Evolutionary Distinctiveness,Threat Status,and Ecological Oddity in Primates

Abstract: The EDGE (evolutionarily distinct and globally endangered) conservation program ( http://www.edgeofexistence.org ) uses a composite measure of threat and phylogenetic isolation to rank species for conservation attention. Using primates as a test case, we examined how species that rank highly with this metric represent the collective from which they are drawn. We considered the ecological and morphological traits, including body mass, diet, terrestriality, and home range size, of all 233 species of primates. Overall, EDGE score and the level of deviance from the mean of 20 different ecological, reproductive, and morphological variables were correlated (mean correlation r =0.14, combined p =1.7 × 10^?14). Although primates with a high EDGE score had characteristics that made them seem odd, they did not seem to express more ancestral characteristics than expected. Sets of primate species with high EDGE scores will, therefore, collectively capture a broader than expected range of the biology of the clade. If similar patterns hold in other groups, the EDGE metric may be useful for prioritizing biodiversity for conservation.     

Development of a new standardised method for sustainable monitoring of the vulnerable pink sea fan Eunicella verrucosa

The aim of this survey was to test a standardised method to follow the demographic evolution of a dense aggregative ‘forest’ population of the temperate gorgonian Eunicella verrucosa (Octocorallia, Gorgoniidae) using in situ photographic recordings. Distribution, density, growth and demographic evolution of the colonies was compared along two parallel transects. Computer treatment allowed the estimation of the total branch fan surface area, and the individual growth of tagged colonies was determined by measuring the increase in this surface area, using consecutive photographs taken at two-year intervals. To integrate the potential bias of branch overlapping, we proposed a correction factor between the in situ photographic surface area and the surface area of the gorgonian calculated from ex situ photographic surface area with all branches deployed. The surface-frequency distribution of colonies was converted to estimated-age-frequency distribution using an estimated growth curve based on the net growth rate. The technique used revealed significant differences in population structure and the dynamics of gorgonian colonies, as the two transects appeared to be influenced by different environmental conditions. The recruitment also seemed to vary according to year and transect, resulting in different densities. Our work showed clear results in characterising the variations of gorgonian demographic evolution at a small spatial scale; thus, it is assumed that this method could be a sustainable tool for coastal environmental managers.     

Ecological drivers of group living in two populations of the communally rearing rodent, Octodon degus

Intraspecific variation in sociality is thought to reflect a trade-off between current fitness benefits and costs that emerge from individuals' decision to join or leave groups. Since those benefits and costs may be influenced by ecological conditions, ecological variation remains a major, ultimate cause of intraspecific variation in sociality. Intraspecific comparisons of mammalian sociality across populations facing different environmental conditions have not provided a consistent relationship between ecological variation and group-living. Thus, we studied two populations of the communally rearing rodent Octodon degus to determine how co-variation between sociality and ecology supports alternative ecological causes of group living. In particular, we examined how variables linked to predation risk, thermal conditions, burrowing costs, and food availability predicted temporal and population variation in sociality. Our study revealed population and temporal variation in total group size and group composition that covaried with population and yearly differences in ecology. In particular, predation risk and burrowing costs are supported as drivers of this social variation in degus. Thermal differences, food quantity and quality were not significant predictors of social group size. In contrast to between populations, social variation within populations was largely uncoupled from ecological differences.     

An invasive riparian tree reduces stream ecosystem efficiency via a recalcitrant organic matter subsidy

A disturbance, such as species invasion, can alter the exchange of materials and organisms between ecosystems, with potential consequences for the function of both ecosystems. Russian olive (Elaeagnus angustifolia) is an exotic tree invading riparian corridors in the western United States, and may alter stream organic matter budgets by increasing allochthonous litter and by reducing light via shading, in turn decreasing in-stream primary production. We used a before-after invasion comparison spanning 35 years to show that Russian olive invasion increased allochthonous litter nearly 25-fold to an invaded vs. a control reach of a stream, and we found that this litter decayed more slowly than native willow. Despite a mean 50% increase in canopy cover by Russian olive and associated shading, there were no significant changes in gross primary production. Benthic organic matter storage increased fourfold after Russian olive invasion compared to pre-invasion conditions, but there were no associated changes in stream ecosystem respiration or organic matter export. Thus, estimated stream ecosystem efficiency (ratio of ecosystem respiration to organic matter input) decreased 14%. These findings show that invasions of nonnative plant species in terrestrial habitats can alter resource fluxes to streams with consequences for whole-ecosystem functions.     

Experimental evidence that workers recognize reproductives through cuticular hydrocarbons in the ant Odontomachus brunneus

Eusociality is characterized by a reproductive division of labor, wherein workers respond to the presence of reproductive individuals by refraining from reproduction themselves and restricting the reproductive efforts of others. Our understanding of how eusociality is maintained therefore depends on characterizing the mechanism by which workers detect the presence of a reproductive. Variations in cuticular hydrocarbons correspond to changes in reproductive ability in ants, and experimental studies are beginning to reveal the function of hydrocarbons as signals. In this study, we compare the cuticular hydrocarbon profiles of dominant and reproductive workers and queens of the ant Odontomachus brunneus with profiles of non-reproductive workers. Using split/reunification tests we document the existence of worker policing in both queenless and queenright colonies; supernumerary reproductives were treated aggressively by nestmates. Finally, we induce aggression and replicate queen-like submissive nestmate responses by supplementing the hydrocarbon profile of workers with (Z)-9-nonacosene, a compound that was significantly more abundant on the cuticles of reproductives. In three bioassays, we compare this manipulation to various control manipulations of the hydrocarbon profile and demonstrate that workers gauge the reproductive activity of nestmates through changes in their cuticular hydrocarbon profiles.