Morphological adaptation of a planktonic diatom to growth in Antarctic sea ice

Chaetoceros dichaeta Ehrenberg is one of the most important planktonic diatom species in the Southern Ocean, making a significant contribution to the total biomass in the region. Our observations on both field and culture material have revealed the existence of a specialized form of C. dichaeta adapted to living in sea ice. This sea ice form differs from the planktonic form by the shape and orientation of the setae and the aperture length between sibling cells. Thus, the diameter of the chain is equivalent to the apical axes of the cells and is accompanied by a two order of magnitude decrease in minimal space requirement. Here, we report for the first time on the extraordinary overwintering strategy of a planktonic diatom in sea ice facilitated by its rapid morphological adaptation to changing environmental conditions. This morphological plasticity enables it to thrive in the confined space of the sea ice brine matrix and retain its numerical dominance in recurrent growing seasons and has likely evolved to optimally exploit the dynamic ecosystem of the seasonally ice-covered seas of the Southern Ocean.     

Coral architecture affects the habitat choice and form of associated gobiid fishes

Gobiid fishes of the genus Gobiodon live in strong association with certain reef-building corals that vary considerably in size and architecture. These fishes hence are excellent model systems for studying evolutionary adaption to specific microhabitats. Using a sample of Gobiodon histrio and G. rivulatus and their most important host corals (Acropora digitifera and A. gemmifera) from the northern Red Sea, we assess (1) how corals that are occupied by gobies differ in their architecture from colonies that are not occupied and (2) how fish body shape is associated with the architecture of their host coral. Fish body shape was assessed by geometric morphometric techniques. Coral measurements included colony size, branch length (BL), and interbranch as well as branch tip distance of adjacent branches, for which we applied a new and non-destructive measurement technique based on casts of two-component epoxy resin. The most important factor influencing the occupation of corals was a BL of more than 5 cm. The distance between coral branches was clearly related to the width of the fishes and hence constrained overall fish size. G. histrio and G. rivulatus differ in adult body shape as well in their allometric development of lateral body compression, resulting in different maximum body sizes attainable in the restricted interbranch space of corals. The strong dependence of coral-associated fishes on large coral colonies with specific architectures increases the extinction risk of fishes within deteriorating coral reefs.     

Flow aeration, cavity processes and energy dissipation on flat and pooled stepped spillways for embankments

The design floods of several reservoirs were recently re-evaluated and the revised spillway outflow could result in dam overtopping with catastrophic consequences for some embankment structures. Herein a physical study was performed on flat and pooled stepped spillways with a slope typical of embankments $(\uptheta = 26.6^{\circ })$ and four stepped configurations were tested: a stepped spillway with flat horizontal steps, a pooled stepped spillway, and two stepped spillways with in-line and staggered configurations of flat and pooled steps. The focus of the study was on the flow aeration, air–water flow properties, cavity flow processes, and energy dissipation performances. The results demonstrated the strong aeration of the flow for all configurations. On the in-line and staggered configurations of flat and pooled steps, the flow was highly three-dimensional. The residual head and energy dissipation rates at the stepped chute downstream end were calculated based upon the detailed air–water flow properties. The results showed that the residual energy was the lowest for the flat stepped weir. The data for the stepped spillway configuration with in-line and staggered configurations of flat and pooled steps showed large differences in terms of residual head in the transverse direction. Altogether the present results showed that, on a $26.6^{\circ }$ slope stepped chute, the designs with in-line and staggered configurations of flat and pooled steps did not provide any advantageous performances in terms of energy dissipation and flow aeration, but they were affected by three-dimensional patterns leading to some flow concentration.     

Applications of GPS-tracked personal and fixed-location PM2.5 continuous exposure monitoring

Continued development of personal air pollution monitors is rapidly improving government and research capabilities for data collection. In this study, we tested the feasibility of using GPS-enabled personal exposure monitors to collect personal exposure readings and short-term daily PM_2.5 measures at 15 fixed locations throughout a community. The goals were to determine the accuracy of fixed-location monitoring for approximating individual exposures compared to a centralized outdoor air pollution monitor, and to test the utility of two different personal monitors, the RTI MicroPEM V3.2 and TSI SidePak AM510. For personal samples, 24-hr mean PM_2.5 concentrations were 6.93 μg/m³ (stderr = 0.15) and 8.47 μg/m³ (stderr = 0.10) for the MicroPEM and SidePak, respectively. Based on time–activity patterns from participant journals, exposures were highest while participants were outdoors (MicroPEM = 7.61 µg/m³, stderr = 1.08, SidePak = 11.85 µg/m³, stderr = 0.83) or in restaurants (MicroPEM = 7.48 µg/m³, stderr = 0.39, SidePak = 24.93 µg/m³, stderr = 0.82), and lowest when participants were exercising indoors (MicroPEM = 4.78 µg/m³, stderr = 0.23, SidePak = 5.63 µg/m³, stderr = 0.08). Mean PM_2.5 at the 15 fixed locations, as measured by the SidePak, ranged from 4.71 µg/m³ (stderr = 0.23) to 12.38 µg/m³ (stderr = 0.45). By comparison, mean 24-h PM_2.5 measured at the centralized outdoor monitor ranged from 2.7 to 6.7 µg/m³ during the study period. The range of average PM_2.5 exposure levels estimated for each participant using the interpolated fixed-location data was 2.83 to 19.26 µg/m³ (mean = 8.3, stderr = 1.4). These estimated levels were compared with average exposure from personal samples. The fixed-location monitoring strategy was useful in identifying high air pollution microclimates throughout the county. For 7 of 10 subjects, the fixed-location monitoring strategy more closely approximated individuals’ 24-hr breathing zone exposures than did the centralized outdoor monitor. Highlights are: Individual PM_2.5 exposure levels vary extensively by activity, location and time of day; fixed-location sampling more closely approximated individual exposures than a centralized outdoor monitor; and small, personal exposure monitors provide added utility for individuals, researchers, and public health professionals seeking to more accurately identify air pollution microclimates.

Implications: Personal air pollution monitoring technology is advancing rapidly. Currently, personal monitors are primarily used in research settings, but could they also support government networks of centralized outdoor monitors? In this study, we found differences in performance and practicality for two personal monitors in different monitoring scenarios. We also found that personal monitors used to collect outdoor area samples were effective at finding pollution microclimates, and more closely approximated actual individual exposure than a central monitor. Though more research is needed, there is strong potential that personal exposure monitors can improve existing monitoring networks.     

Changes in Lumbriculus variegatus metabolites under hypoxic exposure to benzo(a)pyrene,chlorpyrifos and pentachlorophenol: Consequences on biotransformation

The regulation of endogenous metabolites is still not fully understood in aquatic invertebrates exposed concurrently to toxicants and hypoxia. Despite the prevalence of hypoxia in the aquatic environment, toxicity estimations seldom account for multiple stressors thereby differing from natural conditions. In this study, we examined the influence of hypoxia (<30% O₂) on contaminant uptake and the composition of intracellular metabolites in Lumbriculus variegatus exposed to benzo(a)pyrene (B(a)P, 3 μg L⁻¹), chlorpyrifos (CPF, 100 μg L⁻¹) or pentachlorophenol (PCP, 100 μg L⁻¹). Tissue extracts of worms were analyzed for 123 metabolites by gas chromatography–mass spectrometry and metabolite levels were then related to treatments and exposure time. Hypoxia markedly increased the accumulation of B(a)P and CPF, which underlines the significance of oxygen in chemical uptake. The oxygen effect on PCP uptake was less pronounced. Succinate and glycerol-3-phosphate increased significantly (p < 0.0001) following hypoxic treatment, whereas sugars, cysteine, and cholesterol were effectively repressed. The buildup of succinate coupled with the corresponding decline in intracellular 2-oxo- and 2-hydroxy glutaric acid is indicative of an active hypoxia inducible factor mechanism. Glutamate, and TCA cycle intermediates (fumarate, and malate) were disturbed and evident in their marked suppression in worms exposed concurrently to hypoxia and PCP. Clearly, hypoxia was the dominant stressor for individuals exposed to B(a)P or CPF, but to a lesser extent upon PCP treatment. And since oxygen deprivation promotes the accumulation of different toxicants, there may be consequences on species composition of metabolites in natural conditions.     

Modelling Gene Flow between Fields of White Clover with Honeybees as Pollen Vectors

The portion-dilution model is a parametric restatement of the conventional view of animal pollination; it predicts the level of pollinator-mediated gene dispersal. In this study, the model was applied to white clover (Trifolium repens) and its most frequent pollinator, the honeybee (Apis mellifera). One of the three parameters in the portion-dilution model is the mean number of flowers a pollinator visits in one foraging bout. An alternative method to estimate this parameter was developed that was not depending on pollinator hive-seeking behaviour. The new estimation method, based on nectar collection, seems to be a good alternative, when reliable observation on visiting behaviour of pollinators is not possible. The gene flow in white clover was modelled. Where fields were assumed to be well separated, and only a low fraction of bees travelled between fields, the gene flow was estimated to be 0.7%, but subjected to large uncertainty. In a worst case scenario with adjacent fields—one with a genetically modified (GM) T. repens cultivar and the other with a conventional T. repens cultivar—and where all arriving bees were expected to transfer GM pollen, the median gene flow was modelled to be 7% with an estimated 95% percentile of 70%. The results show that the European Union threshold limit of 0.9% GM admixture for food and feed will likely be exceeded at times and especially organic farmers that do not accept GM admixture and often have clover and clover–grass fields might face challenges with admixture of GM.     

Indoor air in schools and lung function of Austrian school children

The Children's Environment and Health Action Plan for Europe (CEHAPE) of WHO focuses (inter alia) on improving indoor environments where children spend most of their time. At present, only little is known about air pollution in schools and its effect on the lung function of school children. Our project was set up as an Austrian contribution to CEHAPE. In a cross-sectional approach, differences in indoor pollution in nine elementary all-day schools were assessed and 34 of these pollutants were analyzed for a relationship with respiratory health determined by spirometry using a linear regression model. Overall 596 children (aged 6-10 years) were eligible for the study. Spirometry was performed in 433 children. Socio-economic status, area of living (urban/rural), and smoking at home were included in the model as potential confounders with school-related average concentration of air pollutants as the variable of primary interest. A negative association with flow volumes (MEF(75)) was found for formaldehyde in air samples, benzylbutylphthalate and the sum of polybrominated diphenylethers in school dust. FVC and FEV(1) were negatively associated with ethylbenzene and xylenes in air samples and tris(1,3-dichlor-2-propyl)-phosphate on particulates. Although, in general, the quality of school indoor air was not worse than that reported for homes, effects on the respiratory health of children cannot be excluded. A multi-faceted strategy to improve the school environment is needed.     

Effects of male sexual harassment on female time budgets,feeding behavior,and metabolic rates in a tropical livebearing fish (<Emphasis Type="Italic">Poecilia mexicana</Emphasis>)

Sexual harassment by males has the potential to affect almost any aspect of female behavior and life history. Using Atlantic mollies (Poecilia mexicana) as a model—a species in which males do not court but almost constantly try to forcefully mate with females—we asked whether and how male harassment influences (a) females’ time budgets and (b) feeding rates (e.g., through frequent flight from male approaches), and (c) whether metabolic rates are increased as a response to stress. Field observations in a natural P. mexicana population revealed that males (average feeding rate 15%) spent far less time feeding than females (60%), and clearly traded off frequent pursuit of females with foraging. Most importantly, females’ feeding times were dramatically reduced when being pursued by a harassing male. Also in standardized lab experiments, females spent significantly less time feeding when accompanied by a male as compared to being in the presence of another female. This effect was also observed when partner fish (male or female) were presented only visually, but could not interact physically with the focal female. It seems, therefore, that females increase vigilance when a harassing male is around, which keeps them from feeding even before males actually approach them. Based on the latter result, we asked whether a stress-induced increase in metabolic rates would be discernible. We measured oxygen consumption and gill ventilation frequencies (opercular rates) of females in different social contexts (alone, with another female, or a male). The predicted, strong body mass dependency of both physiological parameters was uncovered, but no evidence for an effect of social context was detected. We argue that male harassment represents such a constant (but non-lethal) stressor for poeciliid females that their metabolic stress responses have adapted to this through habituation.     

Aggregations and offshore movements as indicators of spawning activity of bonefish (Albula vulpes) in The Bahamas

To identify the timing and location of spawning activity for bonefish (Albula spp.) in the Bahamian archipelago, we used an acoustic telemetry array spanning 44?km² of shallow tidal creeks, flats, and adjacent deeper coastal waters near Cape Eleuthera. In two successive years, we surgically implanted transmitters in male and female bonefish (n?=?60) and examined their movement patterns within the array. Eight bonefish surgically implanted with transmitters as part of an earlier study were also tracked. In 2009, the telemetry information was complemented with snorkeling observations, underwater video, and manual tracking of the same acoustically tagged fish, as well as fish (n?=?3) gastrically implanted with continuous transmitters. During a period of 4?C7?days spanning the full and new moons, primarily between October and May, bonefish moved from their typical shallow flats and aggregated at sites in close proximity to the deep water drop-off of the Exuma Sound. Localized movements of the large schools of bonefish (often?>1,000 fish) at these presumptive pre-spawning aggregation sites included brief trips (<8?h) just after sunset until just prior to sunrise to the abyssal wall at the edge of the Exuma Sound (i.e.,?>1,000?m depth). Tagged bonefish detected at these aggregation sites were subsequently detected back in the tidal creeks and coastal flats shortly after new and full moons and remained at these more typical shallow sites (i.e.,?<2?m depth). Although we did not directly observe spawning events, we did observe ventral nudging and porpoising behaviors, which are potentially associated with courtship. Timing of the observed movements and possible courtship behaviors was coincident with periods when gametes were well developed. Collectively, our study provides the first objective evidence suggesting that the aggregation and seasonal migration of bonefish to deep shelf environments during certain moon phases is for spawning.