The addition of iron to high-nutrient, low-chlorophyll regions induces phytoplankton blooms that take up carbon. Carbon export from the surface layer and, in particular, the ability of the ocean and sediments to sequester carbon for many years remains, however, poorly quantified. Here we report data from the CROZEX experiment in the Southern Ocean, which was conducted to test the hypothesis that the observed north-south gradient in phytoplankton concentrations in the vicinity of the Crozet Islands is induced by natural iron fertilization that results in enhanced organic carbon flux to the deep ocean. We report annual particulate carbon fluxes out of the surface layer, at three kilometres below the ocean surface and to the ocean floor. We find that carbon fluxes from a highly productive, naturally iron-fertilized region of the sub-Antarctic Southern Ocean are two to three times larger than the carbon fluxes from an adjacent high-nutrient, low-chlorophyll area not fertilized by iron. Our findings support the hypothesis that increased iron supply to the glacial sub-Antarctic may have directly enhanced carbon export to the deep ocean. The CROZEX sequestration efficiency (the amount of carbon sequestered below the depth of winter mixing for a given iron supply) of 8,600 mol mol(-1) was 18 times greater than that of a phytoplankton bloom induced artificially by adding iron, but 77 times smaller than that of another bloom initiated, like CROZEX, by a natural supply of iron. Large losses of purposefully added iron can explain the lower efficiency of the induced bloom(6). The discrepancy between the blooms naturally supplied with iron may result in part from an underestimate of horizontal iron supply.

The annual phytoplankton bloom occurring north of the Crozet Plateau provides a rare opportunity to examine the hypothesis that natural iron fertilisation can alleviate HNLC conditions normally associated with the Southern Ocean. Therefore, during CROZEX, a large multidisciplinary study performed between November 2004 and January 2005, measurements of total dissolved iron (DFe, 0.2 m) were made on seawater from around the islands and atmospheric iron deposition estimated from rain and aerosol samples. waters. Enrichment of dissolved iron (>1 nM) at close proximity to the islands suggests that the plateau and the associated sediments are a source of iron. Waters further north also appear to be affected by this input of coastal and shelf origin, although dissolved iron concentrations decrease as a function of distance to the north of the plateau with a gradient of ~ 0.07 nM.km -1 at the time of sampling. Using lateral and vertical diffusion coefficients derived from Ra isotope profiles and also estimates of atmospheric inputs, it was then possible to estimate a DFe concentration of ~ 0.55 nM to the north of the islands prior to the bloom event, which is sufficient to initiate the bloom, the lateral island source being the largest component. A similar situation is observed for other Sub-Antarctic Islands such as Kerguelen, South Georgia, that supply dissolved iron to their surrounding waters, thus, enhancing chlorophyll concentrations.Keywords: Dissolved Iron, Crozet Islands, Southern Ocean, HNLC. Planquette et al., 26/04/07 3 The hypothesis that iron can act as a limiting micro nutrient in High Nutrient Low Chlorophyll (HNLC hereafter) regions is now generally accepted and has been investigated on a number of occasions (Boyd et al., 2000;de Baar et al., 2005). IntroductionThe iron hypothesis originally proposed by Martin (1990) has led to numerous studies which all demonstrate that the addition of iron to HNLC waters causes an increase in phytoplankton productivity. Subsequent investigations into iron's role in phytoplankton physiology have also revealed important findings. Among them, one can cite its role in photosynthetic and respiratory electron transport, nitrate reduction, and chlorophyll synthesis (Sunda and Huntsman, 1995; Sunda and Huntsman, 1997). The broader implication is that in HNLC waters, the presence of iron can increase the efficiency of the biological pump and promote drawdown of atmospheric carbon dioxide (Bakker et al., 2001;Bakker et al., 2005; Boyd et al., 2004; Law et al., 2006;Martin et al., 1990).The Southern Ocean is subjected to these HNLC conditions and is depicted as the largest potential sink of anthropogenic CO 2 in the global ocean (Martin, 1990; Tréguer and Pondaven, 2001) and as a key system in the context of climate change (Sarmiento et al., 1998). However, due to the existence of distinct regional sub systems differing in their physical and biological properties (Arrigo et al., 1998; Tréguer and Jacques, 1992), this ocean should not be viewed as one entity.Ther...

Simple leaching protocols have been used to examine trends in the solubility of aerosol nutrients (Fe, P and Si) along a west – east transect through the Saharan dust plume (German SOLAS cruise M55) and between Saharan and southern hemisphere‐origin aerosols. Solubilities were in the range 0.5–7.9% for Fe, 2.3–67% for P and 0.02–1.1% for Si, with lower values corresponding to samples of Saharan origin. Previous laboratory studies have suggested that aerosol Fe solubility might be enhanced by acid‐ and/or photo‐chemistry during transport through the atmosphere, but only the solubility of P was observed to be higher at the western end of the transect than the eastern. This implies that if (photo)chemical processing of aerosol Fe occurs in the atmosphere, significant enhancement of Fe solubility requires longer than the 5–10 days associated with transport of Saharan dust across the tropical Atlantic Ocean.

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A novel technique for obtaining time-integrated 99Tc concentrations in seawater has been developed, using diffusive gradients in thin films (DGT). The performance of TEVA resin as a binding agent for 99Tc was investigated via laboratory experiments. The accumulated 99Tc activity per unit area of resin−gel was proportional to both the bulk solution activity and the exposure time for deployments of up to 2 weeks. The response of DGT was found to be independent of solution chemistries over the pH range 3−8 and ionic strength range 0.01−1.3 M. Seawater has pH 8 and ionic strength of ∼0.7 M; therefore, the potential of the technique for field deployment in seawater was demonstrated. Detection limits of 0.05 and 0.025 Bq L-1, for 2- and 4-week DGT deployments, respectively, were calculated for 99Tc measurement by liquid scintillation spectrometry. Using quadrupole ICPMS to measure bound 99Tc could reduce these detection limits to 0.125 mBq L-1 for a 4-week deployment. These detection limits are sufficiently low for monitoring contaminated environments, including the Irish Sea. This method is simpler and faster than other 99Tc analysis methods and represents the only means of obtaining time-integrated data.

Background Choking is one of the leading causes of death among unintentional injuries in young children. Food choking represents a considerable public health burden, which might be reduced through increased effective preventative education programs. We present a protocol for a community intervention trial termed CHOP (CHOking Prevention project) that aimed to teach Italian families how to prevent food choking injuries and increase knowledge relating to nutrition. Methods Italian educational facilities were enrolled. Stratified randomization blocked by geographical area was performed. Each stratum was randomized to one of three different intervention strategies or to a control group. Educational intervention was delivered in the schools by experts and certified trainers as per the following three intervention strategies: directly to families (Strategy A); to teaching staff only, who subsequently delivered the same educational intervention to families (Strategy B); to health service staff only, who then delivered the educational intervention to teaching staff, who subsequently delivered the intervention to families (Strategy C). Participants completed a questionnaire about their knowledge on the topics presented during the educational interventions (pre-, post-, and follow-up of intervention). Information from the questionnaires was synthetized into 6 indicators in order to measure how effective each intervention strategy was. Discussion The issue of food choking injuries in children is relevant to public health. The protocol we present provides an opportunity to progress towards overcoming such challenges through a working model that can be implemented also in other countries. Trial registration ClinicalTrials.gov NCT03218618. The study was registered on 14 July 2017.

Choking injuries in children represent a severe public health burden. Although most choking injuries are due to food, parents have often been found to be unaware of the choking hazards presented by food. In this context, healthcare professionals may play an important role in choking prevention by educating families. We investigate the perception of choking injury risk among healthcare profession students by comparing their awareness and knowledge of choking hazards with those of people without a specific health education. A survey was conducted among a sample of final year healthcare profession students from two universities in northern Italy and a sample of adults from the general population without any health education.Respondents were asked to look at ten pictures and identify the items that pose the greatest choking hazard to children of different age groups. Seventy-one students and 742 adults without any health education responded to the survey. A higher percentage of the adults without a health education identified a food item as posing the greatest choking hazard in comparison to the percentage of healthcare profession students. The results of this study suggest that there is a need to include specific educational modules on choking prevention in healthcare-related degree programs.

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