Effects of off-road vehicles on coastal foredunes at Fire Island,New York,USA

The effects of off-road vehicles (ORVs) on the dune system of Fire Island National Seashore, New York, USA, were examined through a detailed, two-year field study. The experimental approach was adopted in order to evaluate the environmental effects of ORVs in this zone. Adjacent control and impact sites were established in two locations. Vehicle impacts were applied at the equivalent rate of one vehicle pass per week. Monitoring of foredune vegetation through sequential quadrat surveys and construction of sea-ward limit maps showed a significant loss of vegetation resulting from ORV impacting. Loss of vegetation resulted in an alteration of the natural foredune profile, which could increase dune erosion during storm wave attack.     

The effects of temperature and resource availability on denitrification and relative N2O production in boreal lake sediments

Anthropogenic environmental stressors(like atmospheric deposition,land use change,and climate warming) are predicted to increase inorganic nitrogen and organic carbon loading to northern boreal lakes,with potential consequences for denitrification in lakes.However,our ability to predict effects of these changes is currently limited as northern boreal lakes have been largely neglected in denitrification studies.The aim of this study was therefore to assess how maximum potential denitrification and N_2O production rates,and the relationship between the two(relative N_2O production),is controlled by availability of nitrate(NO_3~-),carbon(C),phosphorus(P),and temperature.Experiments were performed using the acetylene inhibition technique on sediments from a small,nutrient poor boreal lake in northern Sweden in 2014.Maximum potential denitrification and N_2O production rates at 4°C were reached already at NO_3~-additions of 106–120 μg NO_3~-–N/L,and remained unchanged with higher NO_3 amendments.Higher incubation temperatures increased maximum potential denitrification and N_2O production rates,and Q10 was somewhat higher for N_2O production(1.77) than for denitrification(1.69).The relative N_2O production ranged between 13% and 64%,and was not related to NO_3~-concentration,but the ratio increased when incubations were amended with C and P(from a median of 16% to 27%).Combined,our results suggests that unproductive northern boreal lakes currently have low potential for denitrification but are susceptible to small changes in NO_3 loading especially if these are accompanied by enhanced C and P availability,likely promoting higher N_2O production relative to N_2.     

Ornamentation predicts reproductive success in female pipefish

In the sex-role reversed pipefish Syngnathus typhle females compete for access to males and males are choosy. Females develop a temporary ornament when competing over mates with other females and when performing nuptial dances with males. This ornament is an amplification of the normal striped pattern in these fishes. We here show experimentally that (1) the contrast of this normal pattern forecasts the extent to which the ornament is shown, (2) contrast and ornamentation honestly signal female quality (egg numbers), (3) contrast and ornamentation accurately predict female mating success, (4) contrast is a phenotypically plastic trait specifically exaggerated under situations of female – female competition, and (5) neither contrast nor ornament are energetically expensive to the females (i.e., they are independent of short-term nutritional status). Hence, as predicted in sex-role reversed species, ornament design is constrained by costs to female fecundity: an energetically demanding ornament would impair on a female's ability to produce eggs. The type of ornament described here is the expected one, costly for reasons other than being energetically expensive to produce. Received: 4 April 1996 / Accepted after revision: 27 October 1996     

Infanticidal and anti-infanticidal strategies in the swallow Hirundo rustica

Summary Five definite and nine suspected cases of infanticide were documented in the swallow Hirundo rustica. Unmated males visited neighbouring nests and removed entire broods during the first days of the nestling period, preferentially from nests owned by young late-breeding individuals. Infanticide followed the disappearance of the male nest owner in 11 of the 14 cases. The unmated infanticidal male later mated with the female victim although renesting during the same season only took place in 12 of the 14 cases. The fraction of unmated males increased with colony size, and infanticide was relatively more common if unmated males were abundant. Females did not engage in extra-pair copulations in order to avoid infanticide. Intense guarding of the nest and its contents prevented infanticide. Nest guarding intensity was higher in colonial compared with solitarily breeding swallows, and guarding intensity increased with colony size. Experimental removal of male swallows during the early nestling period reduced the nest guarding intensity and increased frequency of visits from unmated males in colonies, but not among solitarily breeding swallows. Colonial nests from which the male was removed suffered from infanticide more often than solitary nests, and nests where infanticide was recorded were guarded significantly less intensely than other nests before the infanticidal incidents.     

Female house martins (Delichon urbica) reduce egg androgen deposition in response to a challenge of their immune system

Female birds deposit in the yolks of eggs substantial amounts of androgens, such as testosterone and androstenedione. These androgens have been shown to speed up nestling development, induce a fast development of ornaments and increase dominance in adults. Experiments in several species have reported that females invest greater amounts of androgens in the eggs fathered by attractive males, suggesting that yolk androgen is a costly investment for either the offspring or the mother. There is some evidence that nestling immunocompetence may be partially suppressed by high levels of yolk androgens, but it is not known whether this is also the case for females. We tested this hypothesis in the house martin by inducing an immune challenge through an injection of sheep red blood cells, a standard challenge of the humoral immune system. Experimental birds laid eggs with lower amounts of yolk androstenedione than controls, and there was a similar non-significant trend for testosterone. Furthermore, the probability of laying a replacement clutch was higher for birds that had laid a first clutch with relatively high levels of yolk testosterone. These results suggest that yolk androgen deposition is limited by immune costs in the female, and that only females in good condition may afford to invest high levels of androgen in eggs in this species.     

Juvenile Survival in a Population of Neotropical Migrant Birds

Determination of population productivity of Neotropical migrant birds and assessment of breeding habitat quality have been based on population densities and nesting success. Data on juvenile survival improve our estimates of population productivity, provide information on factors during the post-fledging period that affect this productivity and, with comparative data, enable us to better assess breeding habitat quality. We present the first estimate of post-fledging juvenile survival in a population of Neotropical migrant birds. We studied post-fledging survival in a population of Wood Thrush ( Hylocichla mustelina) in southern Missouri, (U.S.) an area hypothesized to contain source populations. Nesting success during our study period was 0.266, and individual survival within the nest was 0.245. Post-fledging survival during the first 8 weeks after fledging was 0.423. Survival varied significantly between post-fledging weekly age classes, with survival of weeks 1, 2, 3, and 4 through 8 being 0.716, 0.930, 0.637, and 1.00, respectively. Probability of predation after fledging was 0.506. Probability of mortality by other causes was 0.071. Probability of predation varied by weekly age class and may have been related to behaviors occurring at different developmental stages. Post-fledging survival was not correlated with nestling mass and did not change throughout the course of the breeding season. Analysis of the source/sink status of the population based on our estimates of nesting success and post-fledging survival indicates that young were being produced below replacement levels during our study period. Large-scale management decisions should take into account potential fluctuations in the productivity of Neotropical migrant populations over time. Data on post-fledging juvenile survival are needed from other populations of Neotropical migrant birds to more accurately assess differential productivity between populations and better assess breeding habitat quality.     

The Rossby Centre Regional Atmospheric Climate Model part I: model climatology and performance for the present climate over Europe

The Rossby Centre Atmospheric Regional Climate Model (RCA2) is described and simulation results, for the present climate over Europe, are evaluated against available observations. Systematic biases in the models mean climate and climate variability are documented and key parameterization weaknesses identified. The quality of near-surface parameters is investigated in some detail, particularly temperature, precipitation, the surface energy budget and cloud cover. The model simulates the recent, observed climate and variability with a high degree of realism. Compensating errors in the components of the surface radiation budget are highlighted and the fundamental causes of these biases are traced to the relevant aspects of the cloud, precipitation and radiation parameterizations. The model has a tendency to precipitate too frequently at small rates, this has a direct impact on the simulation of cloud-radiation interaction and surface temperatures. Great care must be taken in the use of observations to evaluate high resolution RCMs, when they are forced by analyzed boundary conditions. This is particularly true with respect to precipitation and cloudiness, where observational uncertainty is often larger than the RCM bias.     

In situ biodegradation determined by carbon isotope fractionation of aromatic hydrocarbons in an anaerobic landfill leachate plume (Vejen,Denmark)

Concentrations and isotopic compositions (13C/12C) of aromatic hydrocarbons were determined in eight samples obtained from the strongly anoxic part of the leachate plume downgradient from the Vejen Landfill (Denmark), where methanogenic, sulfate-reducing and iron-reducing conditions were observed. Despite the heterogeneous distribution of the compounds in the plume, the isotope fractionation proved that ethylbenzene and m/p-xylene were subject to significant biodegradation within the strongly anoxic plume. The isotope fractionation factors (alphaC) for the degradation of the m/p-xylene (1.0015) and ethylbenzene (1.0021) obtained from the field observations were similar to factors previously determined for the anaerobic degradation of toluene and o-xylene in laboratory experiments, and suggest that in situ biodegradation is one major process controlling the fate of these contaminants in this aquifer. The isotope fractionation determined for 1,2,4-trimethylbenzene and 2-ethyltoluene suggested in situ biodegradation; however, the isotopic composition did not correlate well with the respective concentration as expressed by the Rayleigh equation. Some other compounds (1,2,3-trimethylbenzene, o-xylene, naphthalene and fenchone) did not show significant enrichments in delta13C values along the flow path. The compound concentrations were too low for accurate isotope analyses of benzene, toluene, 1- and 2-methylnaphthalene, while interferences in the chromatography made it impossible to evaluate the isotopic composition for 4-ethyltoluene, 1,3,5-trimethylbenzene and camphor.In addition to demonstrating the potential of assessing isotopic fractionation as a means for documenting the in situ biodegradation of complex mixtures of aromatic hydrocarbons in leachate plumes, this study also illustrates the difficulties for data interpretation in complex plumes and high analytical uncertainties for isotope analysis of organic compounds in low concentration ranges.     

Recovery from eutrophication: experiences of reduced phosphorus input to the four largest lakes of Sweden

In-lake concentration changes of phosphorus (P) and nitrogen (N) in lakes V?ttern, V?nern, M?laren, and Hj?lmaren in response to diminished input has been examined from the mid-1960s onwards. In the former two deep and oligotrophic lakes with slow water renewal, drastic reductions in P-input from the middle of 1970s caused just minor reductions in P-concentration over a very long time. At the same time accumulation occurred in the water mass of inorganic N and possible reasons are discussed. In the latter two mesotrophic to hypertrophic lakes, two shallow basins in L. Hj?lmaren showed slow recovery due to release of P from sediments. The same basins and two basins in L. M?laren have suffered from N-deficiency, particularly during the pre-phosphorus reduction years, and nitrogen fixation was indicated. In two L. M?laren basins recovery of in-lake P concentrations was better than expected in comparison to the so-called IMSA-model for lake recovery from nutrient pollution. In the other five lakes/basins chlorophyll concentrations after 20 years were similar compared to those modeled.     

Representativity of a Mid-lake Surface Water Chemistry Sample

A mid-lake sample is the conventional sampling strategy used in lake chemistry monitoring programs. Hence, addressing the question of how representative a mid-lake sample is of in-lake conditions is important for interpreting changes in long-term monitoring programs. Our hypotheses were that; (i) the location of a sampling site within a lake will affect its representativity and (ii) a mid-lake sample could be considered representative of average surface water physico-chemistry. We focused on the surface water chemistry in 34 Swedish lakes. To obtain a wide diversity of lake types, the lakes were classified according to mean depth, water residence time, and three main ecoregions. Two sampling seasons were selected, representative of high and low biological activity and stratified and non-stratified conditions, respectively. Ten samples were collected in each lake. The mid-lake samples differed significantly from the nine remaining samples in less than 4% of the total number of two-sample t-tests performed. Samples collected close to lake inlets differed from the other samples more often than samples collected in the central parts of the lakes. We concluded that the location of a sampling site within a lake may affect the sample's representativity of lake water chemistry, and that a mid-lake surface water sample could be considered representative of surface water chemistry.