Effects of the herbicide Roundup on freshwater microbial communities: a mesocosm study

The impact of the widely used herbicide glyphosate has been mainly studied in terrestrial weed control, laboratory bioassays, and field studies focusing on invertebrates, amphibians, and fishes. Despite the importance of phytoplankton and periphyton communities at the base of the aquatic food webs, fewer studies have investigated the effects of glyphosate on freshwater microbial assemblages. We assessed the effect of the commercial formulation Roundup using artificial earthen mesocosms. The herbicide was added at three doses: a control (without Roundup) and two treatments of 6 and 12 mg/L of the active ingredient (glyphosate). Estimates of the dissipation rate (k) were similar in the two treatments (half-lives of 5.77 and 7.37 d, respectively). The only two physicochemical parameters showing statistically significant differences between treatments and controls were the downward vertical spectral attenuation coefficient kd(lambda), where lambda is wavelength, and total phosphorus concentration (TP). At the end of the experiment, the treated mesocosms showed a significant increase in the ratio kd(490 nm)/k(d)(550 nm) and an eightfold increase in TP. Roundup affected the structure of phytoplankton and periphyton assemblages. Total micro- and nano-phytoplankton decreased in abundance in treated mesocosms. In contrast, the abundance of picocyanobacteria increased by a factor of about 40. Primary production also increased in treated mesocosms (roughly by a factor of two). Similar patterns were observed in the periphytic assemblages, which showed an increased proportion of dead: live individuals and increased abundances of cyanobacteria (about 4.5-fold). Interestingly, the observed changes in the microbial assemblages were captured by the analysis of the pigment composition of the phytoplankton, the phytoplankton absorption spectra, and the analysis of the optical properties of the water. The observed changes in the structure of the microbial assemblages are more consistent with a direct toxicological effect of glyphosate rather than an indirect effect mediated by phosphorus enrichment.     

Ground-level ozone mapping in large urban areas using multivariate statistical analysis: application to the São Paulo Metropolitan Area

A statistical study on the behavior of ground-level O3 concentration in different regions of a large urban area was carried out, with emphasis on pollutant gas concentrations and meteorological variables. The study was based on data generated by a network of measuring stations distributed throughout the S?o Paulo Metropolitan Area, in regions with different characteristics of traffic and economic activities. The combined application of principal component analysis and clustering techniques to data collected from 1997 until 2000 has led to the identification of implicit relationships between variables that have been associated with dominant processes related to O3 formation in different locations. Similarities between different regions of the city have also been detected and associated with local characteristics. The results indicate that the application of such statistical techniques to data collected in large urban areas enables the grouping of different regions according to their behavior in terms of O3 levels, as well as the identification of dominant processes in each group. These techniques are thus important in the planning of air pollution policies, especially in the case of O3, a pollutant that is not directly related to pollution levels alone.     

Tradescantia pallida cv. purpurea boom in the characterization of air pollution by accumulation of trace elements

Tradescantia pallida cv. purpurea, a plant species widely employed for ornamentation in Brazil, has been successfully used for monitoring the genotoxicity of various agents by the micronucleus assay. To amplify knowledge about its suitability as a bioindicator species, its capacity for accumulating trace elements from urban air pollution was evaluated. T. pallida was rooted using standardized soil, and the vases were distributed in two highly polluted sites of the urban area of S?o Paulo, Brazil (Cerqueira Cesar and Congonhas districts), and in one unpolluted control site situated approximately 50 km from downtown S?o Paulo (in Caucaia do Alto). Approximately six months after exposure to pollutants, adult leaves of this plant were collected monthly for 12 months. The leaves were washed with deionized water, dried, and ground for analyses. Characterization of element levels was carried out by neutron activation analysis. Powdered samples and standards were irradiated at the IEA-R1 nuclear reactor for short and long periods, and concentrations of As, Ba, Br, Ca, Ce, Cl, Cr, Co, Fe, K, La, Mn, Na, Rb, Sb, Sc, Sr, Th, and Zn were determined. Analysis of variance applied to the results indicated that samples from polluted sites present the highest concentrations of Ba, Ce, Cr, Co, Fe, La, Sb, and Sc (p < 0.05). Discriminant analysis revealed that it was possible to distinguish the two polluted areas with a precision of 97.5%, based on the amount of pollutant elements measured in the plants at each site. The results indicated the potential use of T. pallida as an accumulator plant for air pollution biomonitoring.     

Landslides into reservoirs and their impacts on banks

Mass wasting processes, like slope failures, on the margins of dam reservoirs, lakes, bays and oceans may generate large water waves that can produce disasters due to flooding over the banks, run up along the shoreline and overtopping dam crests. Therefore, the study of slope failures, the subsequent generation of impulse waves and their consequences are of paramount importance for safety. In this paper the generation and propagation of water waves in reservoirs induced by landslides and their impact on banks were investigated by means of a laboratory study carried out at University of Coimbra wave channel, in a flume measuring 12.0 m  ×  1.5 m  ×  1.0 m (L  ×  H  ×  W), where two banks with variable slope were placed. The study considered the sliding of calcareous blocks over a sliding slope bank into the reservoir, the generation of impulse waves, their propagation in the reservoir and their impact on the downstream bank. A number of waves were generated by different fallings of calcareous blocks, considering different volumes, sliding slopes, initial positions and reservoir depths. All fallings were recorded by video-camera and the results were processed afterwards to obtain the time history of the falling. The water surface variations due to transient waves were measured at five gauges placed between the banks. The waves overtopping and breaking on the downstream bank were also filmed using a video camera, and the hydrodynamic forces on this bank were also measured using four pressure transducers.     

A simple voltammetric procedure for speciation and evaluation of As removal from water

Here, we show a fast and sensitive method for the determination of inorganic arsenic in natural waters using differential pulse cathodic stripping voltammetry. All the arsenite determinations were done in 2.0 mol L⁻¹ HCl + 3.15 × 10⁻⁴ mol L⁻¹ Cu(II) supporting electrolyte. 1 × 10⁻³ mol L⁻¹ sodium thiosulphate was used as As(V) reducing agent. The detection limit was 0.5 μg L⁻¹ for both species. The method has been applied to water samples collected in an arsenic-contaminated region of Brazil, in particular, to verify the efficiency of the solar oxidation and removal of arsenic process applied to these waters.     

Exploitation of carbohydrate food sources in <Emphasis Type="Italic">Polybia occidentalis</Emphasis>: social cues influence foraging decisions in swarm-founding wasps

An efficient exploitation of carbohydrate food sources would be beneficial for social wasp species that store nectar within their nest. In the swarm-founding polistine wasp Polybia occidentalis, we now demonstrate that the decisions of when and where to forage are influenced by information from conspecifics. Only when foragers had been trained to collect at artificial carbohydrate feeders did newcomers (food-source-naive individuals) continuously arrive at these feeders during 2 h of experiment. In control tests, in which no forager had been trained, not a single newcomer alighted at any of the offered carbohydrate food sources. This indicates that, during the foraging process, a nest-based input provided by successful foragers must have stimulated nestmates to search for food. Once activated, the newcomers’ choice on where to collect was strongly influenced by field-based social information. The mere visual presence of accumulated conspecifics (wasp dummies placed on one of the feeders) attracted newcomers to the food sources. Interestingly, however, visual enhancement was not the only decision-biasing factor at the feeding site. In an experimental series where searching wasps had to choose between the experimental feeder at which 3 foragers continuously collected and the control feeder with nine wasp dummies, only 40% of the wasps chose the visually enhanced feeder. This points to the existence of additional mechanisms of local enhancement. The possibility that, in social wasps, recruitment is involved in the exploitation of carbohydrate food sources is discussed.     

Mercury pollution and childhood in Amazon riverside villages

Mercury is a hazardous metal responsible for environmental contamination and human intoxication. Methylmercury, a very toxic organic compound, bio-accumulates through food chain, and is responsible for chronic mercury exposure of riverside Amazonian communities with a diet rich in fish. Uncertainties about the reference exposure dose that could have damaging consequences for nervous system development makes necessary the biomonitoring of these Amazonian populations, especially children. In this work, a comparative study was performed in exposed and non-exposed children living in the Amazon. A total of 168 children were analyzed to find possible correlations between gender, age, location, and hair mercury content. For each location, no statistically significant differences (P<0.05) were detected for gender and age versus mercury content. However, mean mercury levels in hair samples may indicate a tendency of boys to average higher hair concentrations. Also, in the community with highest levels of mercury, the limit of 10 micro g/g of mercury was surpassed by 65% of 2-6 years and 50% of 7-12 years children but only by 27% of 0-1 year babies, pointing to a lower bioaccumulation and/or the existence of a protection mechanism in babies. Log normal distributions of mercury concentrations for each location showed that children from populations under influence of gold mining activity contain the highest mercury levels in hair samples, though this intoxication may have decreased when compared to previous studies. Knowledge originated by this monitoring will better assist in the development of prevention strategies and government actions targeting the mercury contamination of Amazonian environment.     

Wave hydrodynamics around a multi-functional artificial reef at Leirosa

This paper describes an application of the Boussinesq-type COULWAVE model to study the wave hydrodynamics in the vicinity of a multi-functional artificial reef (MFAR). This reef is under investigation and consists of a supplementary protection solution for the Leirosa sand dune system located at South of Figueira da Foz, on the Portuguese West coast. Such installation near the coastline is expected to contribute to enhance the surfing conditions in the area, protect the sand dune system in the surroundings of Leirosa beach, and increase its environmental value. Numerical calculations with the COULWAVE model were performed for four test cases, considering two reef geometries (differing in the reef angle) and two incident wave conditions (storm condition and a common wave condition). Comparisons between the results obtained, in terms of wave heights and breaking line positions allow us to assess the influence of the reef on the hydrodynamics near the beach and around the reef. Moreover, the reef performance was analysed in terms of surfability and coastal protection. The surfability parameters (breaker height, Iribarren number and peel angle) were calculated for each test case using the numerical wave heights, wave directions and wave breaking positions. Comparisons of parameters allow characterizing the most appropriate configuration of the reef to improve the surfing conditions in the study area. A methodology based on numerical free surface elevations and horizontal velocity components was developed to calculate wave directions, since this is not a direct output of the COULWAVE model. Concerning coastal protection, analyses of the mean currents around the reef were used together with observations of the velocity cells near the shoreline as an indication of the sediment transport.     

Co-occurrence of three types of egg policing in the Norwegian wasp <Emphasis Type="Italic">Dolichovespula norwegica</Emphasis>

In insect societies, workers often try to challenge the reproductive monopoly of the queen by laying their own eggs. Successful worker reproduction, however, is frequently prevented by queen policing or worker policing, whereby either the mother queen or non-reproductive workers selectively kill worker-laid eggs. Recently, a third mechanism—“selfish” worker policing—has also been described in which the workers selectively police worker-laid eggs but also lay eggs themselves. Here, we present results from the monogynous wasp Dolichovespula norwegica, which show that all three kinds of policing—queen policing, worker policing and “selfish” worker policing—co-occur. The net effect of these three kinds of policing collectively favoured the queen’s reproduction, as within 1 day 44% of the worker-laid eggs versus only 8% of the queen-laid eggs were eaten. Of the worker-laid eggs that were killed by workers, approximately two thirds were eaten by the reproductive workers even though these made up only a small proportion, 8%, of the work force. This means that policing workers obtained both direct fitness benefits as well as indirect (inclusive) fitness. In addition, we show that worker policing was carried out by a limited, specialised set of workers that was estimated to constitute approximately one quarter of the whole colony and of which 66% were non-reproductive.     

Factors affecting energy saving behaviour: a prospective research

The purpose of this study is to outline the theme of saving energy resources and its relationship with the preservation of the environment, as well as the importance of green marketing in achieving sustainability. The model of data collection was a survey conducted by self-administered questionnaire. After collection, the data were statistically analysed and interpreted. Most individuals claim to be concerned about environmental problems, with 68% of these belonging to the ‘Savers’ group. However, even though they may be concerned with environmental problems, the vast majority of individuals do not have any system of renewable energy in their homes, despite claiming that renewable energies are a viable option for protecting the environment. Women display behaviour that is more favourable to the saving of energy resources than do men. Educational levels are not significant for distinguishing the more pro-environmental individuals from the others.