Post-larval development of two intertidal barnacles at elevated CO2 and temperature

Ocean acidification and global warming are occurring concomitantly, yet few studies have investigated how organisms will respond to increases in both temperature and CO₂. Intertidal microcosms were used to examine growth, shell mineralogy and survival of two intertidal barnacle post-larvae, Semibalanus balanoides and Elminius modestus, at two temperatures (14 and 19°C) and two CO₂ concentrations (380 and 1,000 ppm), fed with a mixed diatom-flagellate diet at 15,000 cells ml⁻¹ with flow rate of 10 ml⁻¹ min⁻¹. Control growth rates, using operculum diameter, were 14 ± 8 μm day⁻¹ and 6 ± 2 μm day⁻¹ for S. balanoides and E. modestus, respectively. Subtle, but significant decreases in E. modestus growth rate were observed in high CO₂ but there were no impacts on shell calcium content and survival by either elevated temperature or CO₂. S. balanoides exhibited no clear alterations in growth rate but did show a large reduction in shell calcium content and survival under elevated temperature and CO₂. These results suggest that a decrease by 0.4 pH_(NBS) units alone would not be sufficient to directly impact the survival of barnacles during the first month post-settlement. However, in conjunction with a 4–5°C increase in temperature, it appears that significant changes to the biology of these organisms will ensue.     

Short- and long-term consequences of prenatal testosterone for immune function: an experimental study in the zebra finch

Hormone-mediated maternal effects play an important role in the formation of a differentiated phenotype. They have been shown to influence a wide array of offspring traits, both early in life and in adulthood. One important offspring trait that is under the influence of maternal androgens is the immune system. In birds, a growing number of studies show that yolk androgens modulate immune function during the chick stage. However, there is a lack of knowledge regarding long-term effects of prenatal androgens on offspring immunity. In this study, we therefore investigated the influence of prenatal testosterone (T) on several measures of immunity in fledgling and adult zebra finches (Taeniopygia guttata). Cell-mediated immune response (towards phytohaemagglutinin, PHA) of fledglings hatching from control eggs was negatively related to brood size, whereas there was no such association for fledglings hatching from eggs with experimentally elevated T levels (T fledglings). Male control fledglings showed reduced mass gain compared to female control fledglings within 24 h after the PHA injection. This pattern was reversed in T fledglings. Total antibody levels in fledglings were not affected by egg treatment. Neither cell-mediated immunity nor total antibody levels in sexually mature zebra finches were influenced by egg treatment. However, there was an immuno-enhancing effect of elevated egg T on both primary and secondary humoral immune responses toward diphtheria and tetanus antigens in ca 5 and 7 month old zebra finches. In addition, the covariation between different immune components differed between T and control offspring, suggesting that egg treatment may have altered the potential trade-offs between different parts of the immune system. Our results suggest that prenatal androgens could be an important factor contributing to individual variation in immune function even in adulthood.     

Impact of the quality of climate models for modelling species occurrences in countries with poor climatic documentation: a case study from Bolivia

The quality of climate models has largely been overlooked as a possible source of uncertainty that may affect the outcomes of species distribution models, especially in the tropics, where comparatively few climatic stations are available. We compared the geographical discrepancies and potential conservation implications of using two different climate models (Saga and Worldclim) in combination with the species modelling approach Maxent in Bolivia. We estimated ranges of selected bird and fern species biogeographically restricted to either humid montane forest of the northern Bolivian Andes or seasonal dry tropical forests (in the Andes and southern lowlands). Saga and Worldclim predicted roughly similar climate patterns of temperature that were significantly correlated. Precipitation layers of both climate models were also roughly similar, but showed important differences. Species ranges estimated with Worldclim and Saga likewise produced different results. Ranges of species endemic to humid montane forests estimated with Saga had higher AUC (Area under the curve) values than those estimated with Worldclim, which for example predicted the occurrence of humid montane forest bird species near Lake Titicaca, an area that is clearly unsuitable for these species. Likewise, Worldclim overpredicted the occurrence of fern and bird species in the lowlands of the Chapare region and well south of the Andean Elbow, where more seasonal biomes occur. By contrast, Saga predictions were coherent with the known distribution of humid montane forests in the northern Bolivian Andes. Estimated ranges of species endemic to seasonal dry tropical forests predicted with Saga and Worldclim were not statistically different in most cases. However, detailed comparisons revealed that Saga was able to distinguish fragments of seasonal dry tropical forests in rain-shadow valleys of the northern Bolivian Andes, whereas Worldclim was not. These differences highlight the neglected influence of climate layers on modelling results and the importance of using the most accurate climate data available when modelling species distributions.     

Development of a hydrothermal time seed germination model which uses the Weibull distribution to describe base water potential

Seed germination has been modelled extensively using hydrothermal time (HTT) models, that predict time to germination as a function of the extent to which seedbed temperature, T, and water potential, Ψ, exceed the base temperature, T_b, and base water potential, Ψ_b, of each seed percentile, g. Within a seed population the variation in time to germination arises from variation in Ψ_b(g) modelled by a normal distribution. We tested the assumption of normality in the distribution of Ψ_b(g) by germinating seed of two unrelated species with non-dormant seed (Buddleja davidii (Franch.) and Pinus radiata D. Don) across a range of constant Ψ at sub-optimal T. When incorporated into a HTT model the Weibull distribution more accurately described both the right skewed distribution of Ψ_b(g) and germination time course over sub-optimal T than the HTT based on the normal distribution, for both species. Given the flexibility of the Weibull distribution this model not only provides a useful method for predicting germination but also a means of determining the distribution of Ψ_b(g).     

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.     

Offspring sex ratios reflect lack of repayment by auxiliary males in a cooperatively breeding passerine

The repayment hypothesis posits that primary sex ratios in cooperative species should be biased towards the helping sex because these offspring “repay” a portion of their cost through helping behavior and therefore are less expensive to produce. However, many cooperatively breeding birds and mammals do not show the predicted bias in the primary sex ratio. Recent theoretical work has suggested that the repayment hypothesis should only hold when females gain a large fitness advantage from the presence of auxiliary adults in the group. When auxiliaries provide little or no fitness advantage, competition between relatives should lead to sex ratios biased towards the dispersing (non-helping) sex. We examined the benefits auxiliaries provide to females and corresponding offspring sex ratios in the red-backed fairy-wren (Malurus melanocephalus), a cooperatively breeding Australian bird with male auxiliary helpers. We found that auxiliaries provide little or no benefit to female reproductive success or survival. As predicted, the population primary sex ratio was biased towards daughters, the dispersing sex, and females with auxiliaries produced female-biased broods whereas females without auxiliaries produced unbiased broods. Moreover, offspring sex ratios were more strongly biased toward females in years when auxiliaries were more common in the population. These results suggest that offspring sex ratios are associated with competition among the non-dispersing sex in this species, and also that females may use cues to assess local breeding opportunities for their offspring.     

Chemical speciation and bioaccessibility of lead in surface soil and house dust,Lavrion urban area,Attiki, Hellas

In the Lavrion urban area study, Hellas, a five-step sequential extraction method was applied on samples of ‘soil’ (n = 224), affected by long-term mining and metallurgical activities, and house dust (n = 127), for the purpose of studying the potential bioaccessibility of lead and other metals to humans. In this paper, the Pb concentrations in soil and house dust samples are discussed, together with those in rocks and children’s blood. Lead is mainly associated with the carbonate, Fe–Mn oxides and residual fractions in soil and house dust. Considering the very low pH of gastric fluids (1–3), a high amount of metals, present in soil (810–152,000 mg/kg Pb) and house dust (418–18,600 mg/kg Pb), could be potentially bioaccessible. Consequently, children in the neighbourhoods with a large amount of metallurgical processing wastes have high blood-Pb concentrations (5.98–60.49 μg/100 ml; median 17.83 μg/100 ml; n = 235). It is concluded that the Lavrion urban and sub-urban environment is extremely hazardous to human health, and the Hellenic State authorities should urgently tackle this health-related hazard in order to improve the living conditions of local residents.     

Soft song is a reliable signal of aggressive intent in song sparrows

Animals frequently use signals to modulate aggressive interactions. Establishing that a signal is aggressive or threatening requires demonstrating that it is more commonly used in agonistic contexts, that it predicts subsequent aggressive behaviors by the sender, and that receivers respond differently to this signal. Like many birds, song sparrows (Melospiza melodia) produce a low-amplitude “soft song” vocalization that has been hypothesized to be an aggressive signal. Soft song meets the first two criteria, but previous research has failed to demonstrate that soft song provokes aggression or that receivers even perceive soft song differently from normal loud song. We used a playback experiment with taxidermic mount presentation to test whether territorial male song sparrows respond differently to loud and soft song playbacks. Subjects reacted more strongly to the soft song playback by approaching the mount more closely, increasing wing wave displays, and increasing the proportion of their own songs that were soft songs, with further trends toward increasing the number of flights and attacks. These results confirm that soft song is a conventional signal of aggression in song sparrows and that increased receiver retaliation maintains its reliability.     

The effect of pulsed versus gradual salinity reduction on the physiology and survival of Halophila johnsonii Eiseman

Plants of Halophila johnsonii Eiseman were exposed, in mesocosms, to either pulsed hyposalinity treatments of 30, 15, 10, and 8 or gradual salinity reductions of two every 2?days. When salinity was pulsed, survivorship (>80?%) and maximum quantum yields (>0.7) were high in the 30 and 15 salinity treatments, but both declined in the 10 and 8 salinity treatments. Leaf osmolality declined with respect to salinity treatment, but the difference between leaf and media osmolality remained relatively constant (675?±?177?mmol?kg^?1). In contrast, when salinity was gradually reduced, survivorship remained high from salinities of 30 to 4, and maximum quantum yields remained high from salinities of 30 to 6. Leaf osmolality declined linearly with respect to media osmolality and, similar to the pulsed treatments, the difference between leaf and media osmolality remained relatively constant from salinities of 30 to 2 (638?±?161?mmol?kg^?1). Trolox equivalent antioxidant capacity declined over time in both pulsed and gradual salinity reduction. The results indicate that H. johnsonii is more tolerant of hyposalinity than has previously been reported and that gradually reducing salinity extended its low-salinity tolerance threshold by approximately a salinity of 10.     

Current state of heavy metal contents in Vienna soils

This study presents the current state of heavy metal contents in both urban and forest soils within the city area of Vienna, Austria. Based on a systematic survey of urban soils and on targeted sampling in forest areas, local and regional anomaly thresholds are derived using statistical methods and considering regional distribution patterns. For urban soils, local anomaly thresholds of elements Cu (60?mg/kg), Hg (0.5?mg/kg), Pb (100?mg/kg) and Zn (200?mg/kg) exceed national guideline values for uncontaminated urban soils and according to Austrian legislation fall into the category “anthropogenic contamination present but no damage to plants, animals or humans detectable”. In forest soils within the city, thresholds are very similar to reference values for similar geological settings outside the city, apart from higher concentrations of elements Cr and Ni (threshold values of 107 and 64?mg/kg, respectively). Grouping urban soils according to land use reveals that Cd contents are 25?% higher, Pb contents 36?% higher, in traffic and industrial areas than in parks and like Cu, Hg and Zn, these elements can be shown to be at least partly caused by anthropogenic contamination. A dependency between heavy metal concentrations in soils and underlying geological units is shown within the flysch zone at the western city margin where the contents of elements Co, Cr, Cu, Ni and V are controlled by geology and reveal distinct differences between geological units. In built-up areas, no clear dependency between heavy metal contents in soils and geology is evident as urban soils represent accumulations by anthropogenic activity rather than in situ weathering products of underlying sediments.