There are many ways to be a mutualist: endophytic fungus reduces plant survival but increases population growth

One of the challenges to quantifying the costs and benefits of symbiosis is that symbionts can influence different components of host fitness. To improve understanding of the ecology of inherited symbionts, we developed general theory for a perennial host-hereditary symbiont interaction, in which symbionts can have independent and potentially opposing effects on host regeneration and survival. The model showed that negative effects on one component of fitness may be outweighed by positive effects on another, leading to a net positive impact of symbiosis on population growth. Model predictions depended on the availability of suitable patches, which influenced the relative contributions of survival vs. regeneration to host fitness. We then used experimental symbiont removal to quantify effects of a hereditary, fungal endophyte on a grass host. Endophyte presence strongly reduced host survival but increased regeneration. Application of the model revealed that negative effects on plant survival were overwhelmed by beneficial effects on regeneration, resulting in stable endophyte persistence at 100% frequency, consistent with field observations. Our work demonstrates the utility of a demographic perspective for predicting the dynamics of symbioses and supports the hypothesis that symbionts function as mutualists when host and symbiont fitness are coupled through vertical transmission.     

Drivers of euphausiid species abundance and numerical abundance in the Atlantic Ocean

Mid-ocean ridges are common features of the world’s oceans but there is a lack of understanding as to how their presence affects overlying pelagic biota. The Mid-Atlantic Ridge (MAR) is a dominant feature of the Atlantic Ocean. Here, we examined data on euphausiid distribution and abundance arising from several international research programmes and from the continuous plankton recorder. We used a generalized additive model (GAM) framework to explore spatial patterns of variability in euphausiid distribution on, and at either side of, the MAR from 60°N to 55°S in conjunction with variability in a suite of biological, physical and environmental parameters. Euphausiid species abundance peaked in mid-latitudes and was significantly higher on the ridge than in adjacent waters, but the ridge did not influence numerical abundance significantly. Sea surface temperature (SST) was the most important single factor influencing both euphausiid numerical abundance and species abundance. Increases in sea surface height variance, a proxy for mixing, increased the numerical abundance of euphausiids. GAM predictions of variability in species abundance as a function of SST and depth of the mixed layer were consistent with present theories, which suggest that pelagic niche availability is related to the thermal structure of the near surface water: more deeply-mixed water contained higher euphausiid biodiversity. In addition to exposing present distributional patterns, the GAM framework enables responses to potential future and past environmental variability including temperature change to be explored.     

Fine-scale distribution of juvenile Atlantic and Mediterranean loggerhead turtles (Caretta caretta) in the Mediterranean Sea

Loggerhead turtles nesting in the Mediterranean Sea exhibit remarkable genetic structuring. This paper tests the hypothesis that young loggerhead turtles from different rookeries do not distribute homogeneously among the major Mediterranean foraging grounds, due to a complex pattern of surface currents. We extracted long fragments of mitochondrial DNA from 275 stranded or bycaught juvenile turtles from six foraging grounds (Catalano-Balearic Sea, Algerian basin, Tyrrhenian Sea, Adriatic Sea, northern Ionian Sea and southern Levantine Sea). We used a Bayesian mixed-stock analysis to estimate the contributions from rookeries in the Mediterranean, the North-west Atlantic and Cape Verde to the studied foraging grounds. Differences were found in the relative contribution of juvenile turtles of Atlantic and Mediterranean origin to each foraging ground. A decreasing proportion of Atlantic juveniles was detected along the main surface current entering the Mediterranean, with a high prevalence of turtles from eastern Florida in the Algerian basin and lower numbers elsewhere. In regard to the turtles of Mediterranean origin, juveniles from Libya prevailed in central and western Mediterranean foraging grounds other than the Algerian basin. Conversely, the Adriatic Sea was characterised by a large presence of individuals from western Greece, while the southern Levantine Sea was inhabited by a heterogeneous mix of turtles from the eastern Mediterranean rookeries (Turkey, Lebanon and Israel). Overall, the distribution of juveniles may be related to surface circulation patterns in the Mediterranean and suggests that fisheries might have differential effects on each population depending on the overlap degree between foraging and fishing grounds.     

Erratum to: Beak colour reflects circulating carotenoid and vitamin A levels in spotless starlings (Sturnus unicolor)

Many colourful sexually selected signals in animals are carotenoid-dependent and, because carotenoids function as antiradicals and immunostimulating molecules, carotenoid-dependent signals may honestly reflect the health state of individuals. Some others nutrients like vitamin A may also enhance health and colouration, but these have rarely been tested alongside carotenoids in colourful birds. Here, we examined whether beak colour of the spotless starling (Sturnus unicolor) reflected circulating levels of carotenoids and/or vitamin A (retinol). Spotless starlings are polygynous, sexually dimorphic birds (i.e. length of chest feathers). The tip of the beaks of male and female spotless starlings is more intensely coloured at the beginning of the breeding season and becomes dull after mating, which may suggest a sexual function. We found that females have a more intensely coloured beak and higher plasma carotenoid concentration than males during mating, and, despite the finding that carotenoid and vitamin A levels were not significantly related; colour intensity was positively correlated with plasma concentration of carotenoids and vitamin A in both sexes. However, adult beak coloration was not associated with carotenoid and vitamin A concentrations after nestlings were hatched. Therefore, beak colouration of spotless starlings provides information about circulating levels of carotenoids and vitamins during the mating season and may potentially function as a reliable signal of physiological status in the context of sexual selection.     

Stress and team performance: principles and challenges for intelligent decision aids

Advances in computer technology and artificial intelligence are providing powerful capabilities for developing intelligent decision aids (IDAs) to support operating teams in managing complex systems. Early system designs, which acted as independent computer advisors, constrained human decision making, were brittle and encountered problems of user acceptance. As a result, there has been a shift towards making IDAs more cooperative in assisting users to make decisions under stress. Although there is a growing body of research on how to design IDAs as collaborate team players, this article provides additional insights by focusing on the competencies manifested by efficient teams in adapting to stress. To this extent, a survey of how teams adapt their decision-making strategies, cooperation patterns and team structure has provided a good basis for proposing design principles for collaborative IDAs. The article concludes with some challenges for further developments in information technology and research needs in the area of teamwork under stress.     

Model for estimation of traffic pollutant levels in northern communities

Using models to estimate the contribution of traffic to air pollution levels from known traffic data typically requires the knowledge of model parameters such as emission factors and meteorological conditions. This paper presents a state-space model analysis method that does not require the knowledge of model parameters; these parameters are identified from measured traffic and ambient air quality data. This method was used to analyze carbon monoxide (CO) in downtown Fairbanks, AK, which is the community of focus for this paper. It was found that traffic contributed, on average, 53% to the total CO levels over the last six winters. The correlation coefficient between the measured and model-predicted daily profiles of the CO concentration was 0.98, and the results were in good agreement with earlier findings obtained via a thorough CO emission inventory. This justified the usability of the method and it was further used to analyze fine particulate matter (PM2.5) in downtown Fairbanks. It was found that traffic contributed, on average, approximately 30% to the total PM2.5 levels over the last six winters. The correlation coefficient between the measured and model-predicted daily profiles of the PM2.5 concentration was 0.98.     

Free and conjugated estrogen exports in surface-runoff from poultry litter-amended soil

Land application of animal manures such as poultry litter is a common practice, especially in states with surplus manure. Past studies have shown that animal manure may contain estrogens, which are classified as endocrine-disrupting chemicals and may pose a threat to aquatic and wildlife species. We evaluated the concentrations of estrogens in surface runoff from experimental plots (5 x 12 m each) receiving raw and pelletized poultry litter. We evaluated the free (estrone, E1; 17beta-estradiol, E2beta; estriol, E3) and conjugate forms (glucuronides and sulfates) of estrogens, which differ in their toxicity. Sampling was performed for 10 natural storm events over a 4-mo period (April-July 2008). Estrogen concentrations were screened using enzyme-linked immunosorbent assay (ELISA), followed by quantification using liquid chromatography with tandem mass spectrometry (LC/MS/MS). Concentrations of estrogens from ELISA were much higher than the LC/MS/MS values, indicating crossreactivity with organic compounds. Exports of estrogens were much lower from soils amended with pelletized poultry litter than the raw form of the litter. No-tillage management practice also resulted in a lower export of estrogens with surface runoff compared with reduced tillage. The concentrations and exports of conjugate forms of estrogens were much higher than the free forms for some treatments, indicating that the conjugate forms should be considered for a comprehensive assessment of the threat posed by estrogens.     

Fluorescent dye tracing for defining chlorinated ethene plume remediation targets

Three fluorescent dye traces were designed by Zapata Incorporated at a large portion of Tinker Air Force Base (AFB) near Oklahoma City, Oklahoma, to replicate the migration of chlorinated ethene plumes from two target source areas and determine if commingling of those plumes has occurred. The target source areas are spatially separated, contributed contaminants into two aquifers, and were to be remediated from two different financial mechanisms. The nature of the shared fiscal responsibility for remediation of the commingled plumes was unclear. Background sampling was performed to verify that the preferred conservative dyes planned for use were suitable for the site. The fluorescent dyes used were fluorescein and eosine. Eosine dye was introduced into two wells in the upper saturated zone (USZ) under Building 3001 in July 2008. Fluorescein dye was introduced into four monitoring wells screened in the lower saturated zone (LSZ) and the lower lower saturated zone (LLSZ) in July 2008 at the industrial wastewater treatment plant. Zapata then conducted a second dye trace using fluorescein dye in a third USZ well to confirm the results of the eosine dye trace in the USZ under Building 3001. © 2010 Wiley Periodicals, Inc.     

Regional climate sensitivity of wetland environments in Rwanda: the need for a location-specific approach

Wetlands are sustaining large communities of people in Rwanda where 10 % of its land surface consists of many local wetlands. Sustainable future management of these numerous wetlands requires a reliable inventory of their location and a dynamic quantitative characterization that allows assessment of their climate change sensitivity. The aim of this study was to assess the importance of climatic factors for determining wetland location at different regional scales. Wetland locations were analyzed and statistically modeled using their location factors with logistic regression. Wetland location probability was determined using topographic (elevation, slope), hydrological (contributing area) and climatic (temperature and rainfall) location factors. A wetland location probability map was made that demonstrated a calibration accuracy of 87.9 % correct at national level compared to an existing inventory, displaying even better fits at subnational level (reaching up to 98 % correct). A validation accuracy of 86.2 % was obtained using an independently collected dataset. A sensitivity analysis was applied to the threshold values used as cutoff value between wetland/non-wetland, demonstrating a robust performance. The developed models were used in a sensitivity scenario analysis to assess future wetland location probability to changes in temperature and rainfall. In particular, wetlands in the central regions of Rwanda demonstrate a high sensitivity to changes in temperature (1 % increase causes a net probable wetland area decline by 12.4 %) and rainfall (+1 % causes a net increase by 1.6 %). This potentially significant impact on wetland number and location probability indicates that climate-sensitive future planning of wetland use is required in Rwanda.     

Modeling the photo-oxidation of dissolved organic matter by ultraviolet radiation in freshwater lakes: implications for mercury bioavailability

Uncertainties in projected ultraviolet (UV) radiation may lead to future increases in UV irradiation of freshwater lakes. Because dissolved organic carbon (DOC) is the main binding phase for mercury (Hg) in freshwater lakes, an increase in DOC photo-oxidation may affect Hg speciation and bioavailability. We quantified the effect of DOC concentration on the rate of abiotic DOC photo-oxidation for five lakes (DOC=3.27-12.3 mg L(-1)) in Kejimkujik National Park, Canada. Samples were irradiated with UV-A or UV-B radiation over a 72-h period. UV-B radiation was found to be 2.36 times more efficient at photo-oxidizing DOC than UV-A, with energy-normalized rates of dissolved inorganic carbon (DIC) production ranging from 3.8×10(-5) to 1.1×10(-4) mg L(-1)J(-1) for UV-A, and from 6.0×10(-5) to 3.1×10(-4) mg L(-1)J(-1) for UV-B. Energy normalized rates of DIC production were positively correlated with DOC concentrations. Diffuse integrated attenuation coefficients were quantified in situ (UV-A K(d)=0.056-0.180 J cm(-1); UV-B K(d)=0.015-0.165 J cm(-1)) and a quantitative depth-integrated model for yearly DIC photo-production in each lake was developed. The model predicts that, UV-A produces between 3.2 and 100 times more DIC (1521-2851 mg m(-2) year(-1)) than UV-B radiation (29.17-746.7 mg m(-2) year(-1)). Future increases in UV radiation may increase DIC production and increase Hg bioavailability in low DOC lakes to a greater extent than in high DOC lakes.