Microbial Activity Response to Solar Radiation across Contrasting Environmental Conditions in Salar de Huasco, Northern Chilean Altiplano

Indexación: Web of Science; Scopus.In high altitude environments, extreme levels of solar radiation and important differences of ionic concentrations over narrow spatial scales may modulate microbial activity. In Salar de Huasco, a high-altitude wetland in the Andean mountains, the high diversity of microbial communities has been characterized and associated with strong environmental variability. Communities that differed in light history and environmental conditions, such as nutrient concentrations and salinity from different spatial locations, were assessed for bacterial secondary production (BSP, H-3-leucine incorporation) response from short-term exposures to solar radiation. We sampled during austral spring seven stations categorized as: (a) source stations, with recently emerged groundwater (no-previous solar exposure); (b) stream running water stations; (c) stations connected to source waters but far downstream from source points; and (d) isolated ponds disconnected from ground sources or streams with a longer isolation and solar exposure history. Very high values of 0.25 mu E m(-2) s(-1), 72 W m(-2) and 12 W m(-2) were measured for PAR, UVA, and UVB incident solar radiation, respectively. The environmental factors measured formed two groups of stations reflected by principal component analyses (near to groundwater sources and isolated systems) where isolated ponds had the highest BSP and microbial abundance (35 microalgae taxa, picoeukaryotes, nanoflagellates, and bacteria) plus higher salinities and PO43- concentrations. BSP short-term response (4 h) to solar radiation was measured by H-3-leucine incorporation under four different solar conditions: full sun, no UVB, PAR, and dark. Microbial communities established in waters with the longest surface exposure (e.g., isolated ponds) had the lowest BSP response to solar radiation treatments, and thus were likely best adapted to solar radiation exposure contrary to ground source waters. These results support our light history (solar exposure) hypothesis where the more isolated the community is from ground water sources, the better adapted it is to solar radiation. We suggest that factors other than solar radiation (e.g., salinity, PO43-, NO3-) are also important in determining microbial productivity in heterogeneous environments such as the Salar de Huasco.http://journal.frontiersin.org/article/10.3389/fmicb.2016.01857/ful

Diagnosis and management of glutaric aciduria type I – revised recommendations

Glutaric aciduria type I (synonym, glutaric acidemia type I) is a rare organic aciduria. Untreated patients characteristically develop dystonia during infancy resulting in a high morbidity and mortality. The neuropathological correlate is striatal injury which results from encephalopathic crises precipitated by infectious diseases, immunizations and surgery during a finite period of brain development, or develops insidiously without clinically apparent crises. Glutaric aciduria type I is caused by inherited deficiency of glutaryl-CoA dehydrogenase which is involved in the catabolic pathways of L-lysine, L-hydroxylysine and L-tryptophan. This defect gives rise to elevated glutaric acid, 3-hydroxyglutaric acid, glutaconic acid, and glutarylcarnitine which can be detected by gas chromatography/mass spectrometry (organic acids) or tandem mass spectrometry (acylcarnitines). Glutaric aciduria type I is included in the panel of diseases that are identified by expanded newborn screening in some countries. It has been shown that in the majority of neonatally diagnosed patients striatal injury can be prevented by combined metabolic treatment. Metabolic treatment that includes a low lysine diet, carnitine supplementation and intensified emergency treatment during acute episodes of intercurrent illness should be introduced and monitored by an experienced interdisciplinary team. However, initiation of treatment after the onset of symptoms is generally not effective in preventing permanent damage. Secondary dystonia is often difficult to treat, and the efficacy of available drugs cannot be predicted precisely in individual patients. The major aim of this revision is to re-evaluate the previous diagnostic and therapeutic recommendations for patients with this disease and incorporate new research findings into the guideline

Variability of zonation patterns in temperate microtidal Uruguayan sandy beaches with different morphodynamic types

Early studies on sandy beach zonation patterns haveshown rather rigid schemes. Recent work has suggested thatzonation changes with morphodynamic type and, in dissipativebeaches, it also changes through time. This last finding leads to theconclusion that at least 1 yr of study is necessary to understandzonation patterns in dissipative sandy beaches. Here we report a 1yr study (from March 1994 to March 1995) of 4 microtidal beacheswith different morphodynamic types situated on the Atlantic coastof Uruguay. We show that zonation patterns (number of zones orbelts) can change through time regardless of beach type. However,the morphodynamic characteristics of the beach seem to affecthow frequently the zonation pattern can change by fusion orsubdivision of zones, and which zones are involved in thoseprocesses. In beaches with flat slopes (toward the dissipativeextremity), the lower zones were frequently fused and divided. Thesame occurred with the medium and upper zones in the beacheswith steeper slopes (towards the reflective extremity). Our resultssuggest that spatial variability of the macrofauna is related tovariability in the position of the swash zone, which in turn dependson beach slope and width. Variability of species distribution wouldalso depend on morphological adaptations of organisms to movein such environments. We suggest 2 mechanisms of speciesmovement to explain the variability in species distribution observedin this study: Swash Mediated Active Movement (SMAM) andAutonomous Active Movement (AAM). The first mechanisminvolves both an active and a passive component. AAM isindependent of swash movements and affects species distributionon the upper levels of the beach

Longshore patterns of distribution of macroinfauna in an Uruguayan sandy beach: an analysis at different spatial scales and their potential causes

Spatial distribution of macrofaunaalong the longshore axis was studied on an exposed (Uruguayan) sandybeach in order to assess (1) its dependence on beach topography,and (2) the validity to extrapolate local distribution patterns to largerspatial scales (i.e. km). The distribution of the isopods Excirolanaarmata and Excirolana braziliensis, the sand crab Emeritabrasiliensis and several species of insects was analyzed at 3spatial scales. A grid sampling was used at small scale(intersample distance: 4 m; extension sampled: 30 to 40 m), atransect design at meso scale (intersample distance 4 to 20 m;extension sampled: 100 to 120 m), and random sampling at largescale (intersample distance: 100 m; extension sampled: 3000 m).Spatial distribution at small and meso scales were describedusing autocorrelation functions, and tested for effects oftopography at meso and large scales using ANOVA and pairedt-tests. We found that at small and meso scales the distribution ofE. armata and E. brasiliensis was patchy and affected by cusptopography. At large scales, the effect of cusp topography wasrestricted to E. armata. E. armata and E. brasiliensis showedlarge-scale aggregations, and E. braziliensis and insects showedlarge-scale patchiness associated with longshore variability insediment water content and dune characteristics. We conclude thatcusp topography affects longshore distribution patterns, and that itis not valid to extrapolate local longshore distribution to largerscales for every species. We suggest that different processesaffecting spatial distribution must be operating at different scales.At small scales, patterns of distribution may be affected by swashtransport of food and/or organisms, involving factors such as beachtopography, swash and animal movements. At larger scales, inaddition to larval and food supply, sediment transport by the windwould play an important role. Spatial patterns of sand transport bythe wind may be affected by longshore changes in vegetationcover on the dune field. We further suggest that there may be a linkbetween the beach and the dune habitats operating at large spatialscales

Swimming ability and burrowing time of two cirolanid isopods from different levels of exposed sandy beaches

Most of the macroinfauna from sandy beaches is highly mobile, emerging out of the sediment when the tide rises, and using theswash to migrate up and down the beach face or feed (searching for prey or carrion). After swash excursions, they usuallyburrow back into the sediment, maintaining zonation at low tide. Therefore, the different species abilities to emerge, movearound and burrow under different swash climates and sediment conditions are expected to influence observed distributionpatterns. Nonetheless, few attempts have been made to understand behavioral mechanisms of these organisms in moving fluids.In this study, we used a flume tunnel to investigate the orientation, swimming ability and burrowing time of two similar species ofcirolanid isopods, Excirolana armata Dana and Excirolana braziliensis Richardson, under current velocities ranging from 5to 30 cm·s-1. E. armata inhabits middle levels of dissipative to intermediate beaches, while E. braziliensis is found towards theupper level of a wider range of beach states. Both species oriented countercurrent above a threshold velocity, which turned outto be significantly lower for E. armata than for E. braziliensis. E. armata proved to be a stronger swimmer as shown by thehigher velocities surmounted, and the less drags experienced at the highest current velocity. E. armata also burrowed fasterthan E. braziliensis. Burrowing time was affected by sediment grain size and water content, but not by water flow. Onceorganisms managed to begin burrowing under different flow conditions, they were not affected by current velocity.Nonsaturated sand precluded burial, while coarse sand retarded it. Differences in the observed patterns of across-beachdistribution may thus be the result of species-specific behavioral responses to swash climate, manifested in swimming ability,burying and orientation in directional flows

Activity rhythms of two cirolanid isopods from an exposed microtidal sandy beach in Uruguay

Activity rhythms of two cirolanid isopods, Excirolana armata and Excirolana braziliensis, were studiedbased on both seasonal field observations and laboratory experiments, at an exposed microtidal sandy beach inUruguay. The natural emergence patterns of both species were observed in the field for 1 year, twice in each season,and correlated to sea level, expected tidal cycles and diel cycles. Laboratory experiments were carried out in order todetect endogenous rhythms of activity and observe how emergence of both species was affected by changes in lightand/or sediment thixotropy. We also compared behavioral strategies of sympatric species that occupy different beachlevels. Sea level (and thus swash zone position) during field sampling did not follow expected tidal cycles for mostsampling occasions. E. armata was observed in activity most of the time, but activity only correlated with sea level onthree out of eight occasions, and only once was correlated to expected tidal cycle. Laboratory results showed thatemergence under constant conditions was rare; changes in sediment thixotropy stimulated emergence, but theresponse was not cyclical; light had little effect on this response. On the other hand, E. braziliensis was fairly scarce inthe water column, but swimming individuals were observed always during the night. They displayed an endogenouscircadian activity pattern in the laboratory which augmented in response to changes in sediment thixotropy. The naturallight/dark cycle modulated both spontaneous and response emergence by increasing day/night differences in activity.In this study E. armata, a midlittoral species more exposed to sea level variations, seemed to rely entirely on differentphysical and/or biological cues to trigger emergence at the appropriate time. E. braziliensis, found mostly in the upperintertidal zone, emerged in a circadian rhythm, which was stimulated by changes in sediment thixotropy and reinforcedby light cycles. The results of this study led us to conclude that on microtidal, unpredictable beaches, local physicaland biological factors can combine to determine different activity strategies in organisms from different intertidal levels