A georeferenced rRNA amplicon database of aquatic microbiomes from South America.

The biogeography of bacterial communities is a key topic in Microbial Ecology. Regarding continental water, most studies are carried out in the northern hemisphere, leaving a gap on microorganism's diversity patterns on a global scale. South America harbours approximately one third of the world's total freshwater resources, and is one of these understudied regions. To fill this gap, we compiled 16S rRNA amplicon sequencing data of microbial communities across South America continental water ecosystems, presenting the first database µSudAqua[db]. The database contains over 866 georeferenced samples from 9 different ecoregions with contextual environmental information. For its integration and validation we constructed a curated database (µSudAqua[db.sp]) using samples sequenced by Illumina MiSeq platform with commonly used prokaryote universal primers. This comprised ~60% of the total georeferenced samples of the µSudAqua[db]. This compilation was carried out in the scope of the µSudAqua collaborative network and represents one of the most complete databases of continental water microbial communities from South America.

Unraveling the ecological processes modulating the population structure of Escherichia coli in a highly polluted urban stream network.

Escherichia coli dynamics in urban watersheds are affected by a complex balance among external inputs, niche modulation and genetic variability. To explore the ecological processes influencing E. coli spatial patterns, we analyzed its abundance and phylogenetic structure in water samples from a stream network with heterogeneous urban infrastructure and environmental conditions. Our results showed that environmental and infrastructure variables, such as macrophyte coverage, DIN and sewerage density, mostly explained E. coli abundance. Moreover, main generalist phylogroups A and B1 were found in high proportion, which, together with an observed negative relationship between E. coli abundance and phylogroup diversity, suggests that their dominance might be due to competitive exclusion. Lower frequency phylogroups were associated with sites of higher ecological disturbance, mainly involving simplified habitats, higher drainage infrastructure and septic tank density. In addition to the strong negative relationship between phylogroup diversity and dominance, the occurrence of these phylogroups would be associated with increased facilitated dispersal. Nutrients also contributed to explaining phylogroup distribution. Our study proposes the differential contribution of distinct ecological processes to the patterns of E. coli in an urban watershed, which is useful for the monitoring and management of fecal pollution.

Surface chemistry modification of silica nanoparticles alters the activation of monocytes.

Aim: Nanoparticles (NPs) interaction with immune system is a growing topic of study. Materials & methods: Bare and amine grafted silica NPs effects on monocytes/macrophages cells were analyzed by flow cytometry, MTT test and LIVE/DEAD® viability/cytotoxicity assay. Results: Bare silica NPs inhibited proliferation and induced monocyte/macrophages activation (increasing CD40/CD80 expression besides pro-inflammatory cytokines and nitrite secretion). Furthermore, silica NPs increased cell membrane damage and reduced the number of living cells. In contrast, amine grafted silica NPs did not alter these parameters. Conclusion: Cell activation properties of bare silica NPs could be hindered after grafting with amine moieties. This strategy is useful to tune the immune system stimulation by NPs or to design NPs suitable to transport therapeutic molecules.

Linking the scientific knowledge on marine frontal systems with ecosystem services.

Primary production hotspots in the marine environment occur where the combination of light, turbulence, temperature and nutrients makes the proliferation of phytoplankton possible. Satellite-derived surface chlorophyll-a distributions indicate that these conditions are frequently associated with sharp water mass transitions named "marine fronts". Given the link between primary production, consumers and ecosystem functions, marine fronts could play a key role in the production of ecosystem services (ES). Using the shelf break front in the Argentine Sea as a study case, we show that the high primary production found in the front is the main ecological feature that supports the production of tangible (fisheries) and intangible (recreation, regulation of atmospheric gases) marine ES and the reason why the provision of ES in the Argentine Sea concentrates there. This information provides support to satellite chlorophyll as a good indicator of multiple marine ES. We suggest that marine fronts could be considered as marine ES hot spots.

Dataset on the TIC-MOC cruise onboard the R/V Hespérides, March 2015, Brazil-Malvinas Confluence.

This oceanographic dataset was gathered during the TIC-MOC cruise, which was designed to characterize the dynamics of the Brazil-Malvinas Confluence. The cruise was carried on board the R/V Hespérides, with departure from Ushuaia and arrival to Salvador de Bahía. A total of 66 conductivity-temperature-depth (CTD) stations were completed between 8 and 22 March 2015, offshore from the continental platform and within 45°S-35°S and 61°W-50°W. At each station, water samples were collected, which were used to calibrate the CTD salinity-oxygen sensors and to determine inorganic nutrient concentrations, and the horizontal current was measured. Along its track, the vessel recorded surface temperature and salinity, as well as the horizontal flow down to about 700 m. Lastly, eight position-transmitting drifters were launched and two profiling floats were deployed and later recovered.

Evidence of size-dependent effect of silica micro- and nano-particles on basal and specialized monocyte functions.

AIM: To analyze the effect of silica particles on monocyte/macrophage functions. MATERIALS & METHODS: Silica micro- and nanoparticles were obtained by the Stöber method. Their effect on monocyte/macrophage proliferation, activation, membrane integrity and metabolic activity were determined. RESULTS: Silica particles inhibit cell proliferation while 10 nm nanoparticles (NPs) did not affect it. Similarly, silica particles induced strong cell activation. However, 10 nm NPs do not alter IL-12 or nitrite levels. Furthermore, bigger NPs and microparticles increase cell membrane damage and reduce the number of living cells but smallest NPs (10 and 240 nm) did not. CONCLUSION: Cell activation properties of silica particles could be useful tools for immune stimulation therapy, while 10 nm NPs would be suitable for molecule transportation.

Altimeter-derived seasonal circulation on the southwest Atlantic shelf: 27°-43°S.

Altimeter sea surface height (SSH) fields are analyzed to define and discuss the seasonal circulation over the wide continental shelf in the SW Atlantic Ocean (27°-43°S) during 2001-2012. Seasonal variability is low south of the Rio de la Plata (RdlP), where winds and currents remain equatorward for most of the year. Winds and currents in the central and northern parts of our domain are also equatorward during autumn and winter but reverse to become poleward during spring and summer. Transports of shelf water to the deep ocean are strongest during summer offshore and to the southeast of the RdlP. Details of the flow are discussed using mean monthly seasonal cycles of winds, heights, and currents, along with analyses of Empirical Orthogonal Functions. Principle Estimator Patterns bring out the patterns of wind forcing and ocean response. The largest part of the seasonal variability in SSH signals is due to changes in the wind forcing (described above) and changes in the strong boundary currents that flow along the eastern boundary of the shelf. The rest of the variability contains a smaller component due to heating and expansion of the water column, concentrated in the southern part of the region next to the coast. Our results compare well to previous studies using in situ data and to results from realistic numerical models of the regional circulation.

The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Satellite observations.

Satellite-derived sea surface salinity (SSS) data from Aquarius and SMOS are used to study the shelf-open ocean exchanges in the western South Atlantic near 35°S. Away from the tropics, these exchanges cause the largest SSS variability throughout the South Atlantic. The data reveal a well-defined seasonal pattern of SSS during the analyzed period and of the location of the export of low-salinity shelf waters. In spring and summer, low-salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36°S to 37°30'S). In contrast, in fall and winter, low-salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The strong seasonal SSS pattern is modulated by the seasonality of the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low-salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low-salinity waters in the open ocean. KEY POINTS: Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies.

The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Numerical simulations.

A high-resolution model is used to characterize the dominant patterns of sea surface salinity (SSS) variability generated by the freshwater discharges of the Rio de la Plata (RdlP) and the Patos/Mirim Lagoon in the southwestern Atlantic region. We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the austral winter (JJA), the plumes leave the shelf region north of the BMC. During the austral summer (DJF), the plumes are entrained more directly into the BMC. A sensitivity study indicates that the high-frequency component of the wind stress forcing controls the vertical structure of the plumes while the low-frequency component of the wind stress forcing and the interannual variations of the RdlP discharge controls the horizontal structure of the plumes. Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean. The net cross-shelf volume flux is 1.21 Sv. This outflow is largely compensated by an inflow from the Patagonian shelf.