Massive inclusion of digital technologies in schools : Argentinian young adolescents? appropriation of computers and the Internet in popular and middle classes

Since the implementation of the Programa Conectar Igualdad (PCI) (Connecting Equality Program) in 2010 in Argentina, numerous Social Science specialists started to research how massive ICT introduction in schools would radically affect teaching and learning processes, knowledge building and youth behaviour. Nevertheless, there is still not much empirical evidence showing the ways in which these technologies are appropriated. This situation discloses the need of placing research questions locally situated with regard to those potential changes. What existing access methods does PCI encounter? And how does its implementation participate in the design of personal and family heterogeneous trajectories of ICTs appropriation? How do the students themselves perceive the infl uence of PCI on their own technologic abilities and competence? How do knowledge and aptitudes associated to new digital media articulate with the knowledge manners promoted by the school format and institutionalism? How does the massive introduction of netbooks affect the interaction among different school actors (students-teachers)? What happens in other sociability and socialization spaces, such as the house and cybercafé?

Chemistry and grain-size distribution of terrigenous sediments deposited at Site GeoB9501

The Sahara Desert is the largest source of mineral dust in the world. Emissions of African dust increased sharply in the early 1970s, a change that has been attributed mainly to drought in the Sahara/Sahel region caused by changes in the global distribution of sea surface temperature. The human contribution to land degradation and dust mobilization in this region remains poorly understood, owing to the paucity of data that would allow the identification of long-term trends in desertification. Direct measurements of airborne African dust concentrations only became available in the mid-1960s from a station on Barbados and subsequently from satellite imagery since the late 1970s: they do not cover the onset of commercial agriculture in the Sahel region ~170 years ago. Here we construct a 3,200-year record of dust deposition off northwest Africa by investigating the chemistry and grain-size distribution of terrigenous sediments deposited at a marine site located directly under the West African dust plume. With the help of our dust record and a proxy record for West African precipitation we find that, on the century scale, dust deposition is related to precipitation in tropical West Africa until the seventeenth century. At the beginning of the nineteenth century, a sharp increase in dust deposition parallels the advent of commercial agriculture in the Sahel region. Our findings suggest that human-induced dust emissions from the Sahel region have contributed to the atmospheric dust load for about 200 years.

Chemistry and stable isotope record of sediment core GeoB4905-4

Evidence of rapid climatic oscillations like those observed in the Greenland ice cores and sediments from high latitudes of the northern Atlantic have been recognized in the pulses of terrigenous material to continental margin sediments off Cameroon. Fe/Ca ratios used as a parameter to quantify the relative proportions of terrigenous fluxes versus marine carbonate monitor the variability of the west African monsoon. They reveal the history of abrupt changes in precipitation over western and central Africa during the past 52 kyr. These rapid changes are particularly pronounced during the last glacial period and occur at timescales of a few thousand years. Stable oxygen isotope (delta18O) records of Globigerinoides ruber (pink) show high negative values reflecting periods of high monsoon precipitation. The Fe/Ca pattern is very similar to the Dansgaard-Oeschger cycles from the Greenland ice cores. The good correspondence between the warm interstadials of the Dansgaard-Oeschger cycles from the GISP2 ice core records and the high pulses of Fe/Ca sedimentation in our core suggest a strong teleconnection between the low-latitude African climate and the high-latitude northern hemisphere climate oscillations during the last glacial. This climatic link is probably vested in the west African monsoonal fluctuation that alters tropical sea surface temperatures, thermohaline circulations and in turn net export of heat from the south to the north Atlantic, coupled with the variability of the low-latitude southeast trade winds.

Seawater carbonate chemistry and sperm swimming speed of the polychaete Galeolaria caespitosa in lab experiment

The rapidity of ocean acidification intensifies selection pressure for resilient phenotypes, particularly during sensitive early life stages. The scope for selection is greater in species with greater within-species variation in responses to changing environments, thus enhancing the potential for adaptation. We investigated among-male variation in sperm swimming responses (percent motility and swimming speeds) of the serpulid polychaete Galeolaria caespitosa to near- (delta pH 0.3) and far-future ocean acidification (delta pH 0.5). Responses of sperm swimming to acidification varied significantly among males and were overall negative. Robust sperm swimming behavior under near-future ocean acidification in some males may ameliorate climate change impacts, if traits associated with robustness are heritable, and thereby enhance the potential for adaptation to far-future conditions. Reduced sperm swimming in the majority of male G. caespitosa may decrease their fertilization success in a high CO2 future ocean. Resultant changes in offspring production could affect recruitment success and population fitness downstream.

Seawater carbonate chemistry and sperm swimming speed, fertilization success of the Australasian sea urchin Heliocidaris erythrogramma in lab experiment

Background: Climate change will lead to intense selection on many organisms, particularly during susceptible early life stages. To date, most studies on the likely biotic effects of climate change have focused on the mean responses of pooled groups of animals. Consequently, the extent to which inter-individual variation mediates different selection responses has not been tested. Investigating this variation is important, since some individuals may be preadapted to future climate scenarios. Methodology/Principal Findings: We examined the effect of CO2-induced pH changes ("ocean acidification") in sperm swimming behaviour on the fertilization success of the Australasian sea urchin Heliocidaris erythrogramma, focusing on the responses of separate individuals and pairs. Acidification significantly decreased the proportion of motile sperm but had no effect on sperm swimming speed. Subsequent fertilization experiments showed strong inter-individual variation in responses to ocean acidification, ranging from a 44% decrease to a 14% increase in fertilization success. This was partly explained by the significant relationship between decreases in percent sperm motility and fertilization success at delta pH = 0.3, but not at delta pH = 0.5. Conclusions and Significance: The effects of ocean acidification on reproductive success varied markedly between individuals. Our results suggest that some individuals will exhibit enhanced fertilization success in acidified oceans, supporting the concept of 'winners' and 'losers' of climate change at an individual level. If these differences are heritable it is likely that ocean acidification will lead to selection against susceptible phenotypes as well as to rapid fixation of alleles that allow reproduction under more acidic conditions. This selection may ameliorate the biotic effects of climate change if taxa have sufficient extant genetic variation upon which selection can act.

Seawater carbonate chemistry and reproduction of the two calanoid copepods Centropages typicus and Temora longicornis in a laboratory experiment

Some planktonic groups suffer negative effects from ocean acidification (OA), although copepods might be less sensitive. We investigated the effect of predicted CO2 levels (range 480-750 ppm), on egg production and hatching success of two copepod species, Centropages typicus and Temora longicornis. In these short-term incubations there was no significant effect of high CO2 on these parameters. Additionally a very high CO2 treatment, (CO2 = 9830 ppm), representative of carbon capture and storage scenarios, resulted in a reduction of egg production rate and hatching success of C. typicus, but not T. longicornis. In conclusion, reproduction of C. typicus was more sensitive to acute elevated seawater CO2 than that of T. longicornis, but neither species was affected by exposure to CO2 levels predicted for the year 2100. The duration and seasonal timing of exposures to high pCO2, however, might have a significant effect on the reproduction success of calanoid copepods.

Seawater carbonate chemistry and morphometric coordinates and morphology of the control 8-arm pluteus of brittlestar Ophiothrix fragilis, 2008

The world's oceans are slowly becoming more acidic. In the last 150 yr, the pH of the oceans has dropped by ~0.1 units, which is equivalent to a 25% increase in acidity. Modelling predicts the pH of the oceans to fall by 0.2 to 0.4 units by the year 2100. These changes will have significant effects on marine organisms, especially those with calcareous skeletons such as echinoderms. Little is known about the possible long-term impact of predicted pH changes on marine invertebrate larval development. Here we predict the consequences of increased CO2 (corresponding to pH drops of 0.2 and 0.4 units) on the larval development of the brittlestar Ophiothrix fragilis, which is a keystone species occurring in high densities and stable populations throughout the shelf seas of northwestern Europe (eastern Atlantic). Acidification by 0.2 units induced 100% larval mortality within 8 d while control larvae showed 70% survival over the same period. Exposure to low pH also resulted in a temporal decrease in larval size as well as abnormal development and skeletogenesis (abnormalities, asymmetry, altered skeletal proportions). If oceans continue to acidify as expected, ecosystems of the Atlantic dominated by this keystone species will be seriously threatened with major changes in many key benthic and pelagic ecosystems. Thus, it may be useful to monitor O. fragilis populations and initiate conservation if needed.

Seawater carbonate chemistry and cell numbers during experiments with dinoflagellates, 2007

The effects of dissolved inorganic carbon (DIC) on the growth of 3 red-tide dinoflagellates (Ceratium lineatum, Heterocapsa triquetra and Prorocentrum minimum) were studied at pH 8.0 and at higher pH levels, depending upon the pH tolerance of the individual species. The higher pH levels chosen for experiments were 8.55 for C. lineatum and 9.2 for the other 2 species. At pH 8.0, which approximates the pH found in the open sea, the maximum growth in all species was maintained until the total DIC concentration was reduced below ~0.4 and 0.2 mM for C. lineatum and the other 2 species, respectively. Growth compensation points (concentration of inorganic carbon needed for maintenance of cells) were reached at ~0.18 and 0.05 mM DIC for C. lineatum and the other 2 species, respectively. At higher pH levels, maximum growth rates were lower compared to growth at pH 8, even at very high DIC concentrations, indicating a direct pH effect on growth. Moreover, the concentration of bio-available inorganic carbon (CO2 + HCO3-) required for maintenance as well as the half-saturation constants were increased considerably at high pH compared to pH 8.0. Experiments with pH-drift were carried out at initial concentrations of 2.4 and 1.2 mM DIC to test whether pH or DIC was the main limiting factor at a natural range of DIC. Independent of the initial DIC concentrations, growth rates were similar in both incubations until pH had increased considerably. The results of this study demonstrated that growth of the 3 species was mainly limited by pH, while inorganic carbon limitation played a minor role only at very high pH levels and low initial DIC concentrations.

Seawater carbonate chemistry and calcification during a tropical lagoon study at SW lagoon, New Caledonia, 1991

A selective chemical photosynthesis inhibitor, DCMU (Dichorophenyl-dimethylurea), dissolved in DMSO (Dimethyl sulfoxide) was substituted for the dark incubation method commonly used to measure the oxygen consumption in metabolic and primary production studies. We compared oxygen fluxes during light incubations with DCMU and dark incubations procedure, on soft bottom benthos. For this purpose, we studied the effects of different DCMU concentrations. A concentration of 5 · 10-5 mol l-1 inside a clear incubation enclosure completely inhibits photosynthesis without affecting the metabolism of soft bottom benthos.

Seawater carbonate chemistry and growth rate during experiments with dinoflagellates, 2007

The effects of dissolved inorganic carbon (DIC) on the growth of 3 red-tide dinoflagellates (Ceratium lineatum, Heterocapsa triquetra and Prorocentrum minimum) were studied at pH 8.0 and at higher pH levels, depending upon the pH tolerance of the individual species. The higher pH levels chosen for experiments were 8.55 for C. lineatum and 9.2 for the other 2 species. At pH 8.0, which approximates the pH found in the open sea, the maximum growth in all species was maintained until the total DIC concentration was reduced below ~0.4 and 0.2 mM for C. lineatum and the other 2 species, respectively. Growth compensation points (concentration of inorganic carbon needed for maintenance of cells) were reached at ~0.18 and 0.05 mM DIC for C. lineatum and the other 2 species, respectively. At higher pH levels, maximum growth rates were lower compared to growth at pH 8, even at very high DIC concentrations, indicating a direct pH effect on growth. Moreover, the concentration of bio-available inorganic carbon (CO2 + HCO3-) required for maintenance as well as the half-saturation constants were increased considerably at high pH compared to pH 8.0. Experiments with pH-drift were carried out at initial concentrations of 2.4 and 1.2 mM DIC to test whether pH or DIC was the main limiting factor at a natural range of DIC. Independent of the initial DIC concentrations, growth rates were similar in both incubations until pH had increased considerably. The results of this study demonstrated that growth of the 3 species was mainly limited by pH, while inorganic carbon limitation played a minor role only at very high pH levels and low initial DIC concentrations.

Seawater carbonate chemistry and impacts of calcium and carbonate ion concentration on Mg and Sr incorporation in cultured benthic foraminifera (Ammonia tepida and Heterostegina depressa), 2011

Laboratory culture experiments were conducted to determine effects of seawater carbonate ion concentration ([CO32-]), and thereby calcite saturation state, on Mg and Sr incorporation into calcite of two species of shallow-water benthic foraminifera: Ammonia tepida and Heterostegina depressa. Impact on Mg and Sr incorporation by increased seawater [CO32-] and thereby higher calcite saturation state, is absent in either species. Comparison to results from a similar culturing experiment, in which calcite saturation state was varied as a function of [Ca2+], reveals that saturation state affects incorporation of Mg and Sr through calcium- rather than carbonate availability. The similarity in response by both species is surprising since the average Mg/Ca ratio is ~ 70 times higher in H. depressa than in A. tepida. Furthermore, these results suggest that the ions involved in biomineralization (i.e. Ca2+ and DIC) are processed by separate cellular transport mechanisms. The similar response of Mg and Sr incorporation in this study suggests that only differences in the Ca2+ transport mechanism affect divalent cation partitioning.

Seawater carbonate chemistry and settlement of a spawning coral on three common species of crustose coralline algae

Concern about the impacts of ocean acidification (OA) on ecosystem function has prompted many studies to focus on larval recruitment, demonstrating declines in settlement and early growth at elevated CO2 concentrations. Since larval settlement is often driven by particular cues governed by crustose coralline algae (CCA), it is important to determine whether OA reduces larval recruitment with specific CCA and the generality of any effects. We tested the effect of elevated CO2 on the survival and settlement of larvae from the common spawning coral Acropora selago with 3 ecologically important species of CCA, Porolithon onkodes, Sporolithon sp., and Titanoderma sp. After 3 d in no-choice laboratory assays at 447, 705, and 1214 µatm pCO2, the rates of coral settlement declined as pCO2 increased with all CCA taxa. The magnitude of the effect was highest with Titanoderma sp., decreasing by 87% from the ambient to highest CO2 treatment. In general, there were high rates of larval mortality, which were greater with the P. onkodes and Sporolithon sp. treatments (~80%) compared to the Titanoderma sp. treatment (65%). There was an increase in larval mortality as pCO2 increased, but this was variable among the CCA species. It appears that OA reduces coral settlement by rapidly altering the chemical cues associated with the CCA thalli and microbial community, and potentially by directly affecting larval viability.

Seawater carbonate chemistry and net photosynthesis, C/N ratio, growth rate, size of Ostreococcus tauri in a laboratory experiment

Phytoplankton are the basis of marine food webs, and affect biogeochemical cycles. As CO2 levels increase, shifts in the frequencies and physiology of ecotypes within phytoplankton groups will affect their nutritional value and biogeochemical function. However, studies so far are based on a few representative genotypes from key species. Here, we measure changes in cellular function and growth rate at atmospheric CO2 concentrations predicted for the year 2100 in 16 ecotypes of the marine picoplankton Ostreococcus. We find that variation in plastic responses among ecotypes is on par with published between-genera variation, so the responses of one or a few ecotypes cannot estimate changes to the physiology or composition of a species under CO2 enrichment. We show that ecotypes best at taking advantage of CO2 enrichment by changing their photosynthesis rates most should increase in relative fitness, and so in frequency in a high-CO2 environment. Finally, information on sampling location, and not phylogenetic relatedness, is a good predictor of ecotypes likely to increase in frequency in this system.

Physical oceanography, pore water chemistry and water column methane turover rates during POLARSTERN cruise ANT-XXIX/4

Recent studies have suggested that the marine contribution of methane from shallow regions and melting marine terminating glaciers may have been underestimated. Here we report on methane sources and potential sinks associated with methane seeps in Cumberland Bay, South Georgia's largest fjord system. The average organic carbon content in the upper 8 meters of the sediment is around 0.65 wt.%; this observation combined with Parasound data suggest that the methane gas accumulations probably originate from peat-bearing sediments currently located several tens of meters below the seafloor. Only one of our cores indicates upward advection; instead most of the methane is transported via diffusion. Sulfate and methane flux estimates indicate that a large fraction of methane is consumed by anaerobic oxidation of methane (AOM). Carbon cycling at the sulfate-methane transition (SMT) results in a marked fractionation of the d13C-CH4 from an estimated source value of -65 per mil to a value as low as -96 per mil just below the SMT. Methane concentrations in sediments are high, especially close to the seepage sites (~40 mM); however, concentrations in the water column are relatively low (max. 58 nM) and can be observed only close to the seafloor. Methane is trapped in the lowermost water mass, however, measured microbial oxidation rates reveal very low activity with an average turnover of 3.1 years. We therefore infer that methane must be transported out of the bay in the bottom water layer. A mean sea-air flux of only 0.005 nM/m²/s confirms that almost no methane reaches the atmosphere.

Seawater carbonate chemistry and calcification during tropical reef studies at Moorea (French Polynesia), 1996

Community metabolism was investigated using a Lagrangian flow respirometry technique on 2 reef flats at Moorea (French Polynesia) during austral winter and Yonge Reef (Great Barrier Reef) during austral summer. The data were used to estimate related air-sea CO2 disequilibrium. A sine function did not satisfactorily model the diel light curves and overestimated the metabolic parameters. The ranges of community gross primary production and respiration (Pg and R; 9 to 15 g C m-2 d-1) were within the range previously reported for reef flats, and community net calcification (G; 19 to 25 g CaCO3 m-2 d-1) was higher than the 'standard' range. The molar ratio of organic to inorganic carbon uptake was 6:1 for both sites. The reef flat at Moorea displayed a higher rate of organic production and a lower rate of calcification compared to previous measurements carried out during austral summer. The approximate uncertainty of the daily metabolic parameters was estimated using a procedure based on a Monte Carlo simulation. The standard errors of Pg,R and Pg/R expressed as a percentage of the mean are lower than 3% but are comparatively larger for E, the excess production (6 to 78%). The daily air-sea CO2 flux (FCO2) was positive throughout the field experiments, indicating that the reef flats at Moorea and Yonge Reef released CO2 to the atmosphere at the time of measurement. FCO2 decreased as a function of increasing daily irradiance.