Recovery of submersed vegetation in a high mountain oligotrophic soft-water lake over two decades after impoundment

Este artículo contiene 13 páginas, 5 figuras, 2 tablas.Recovery of the submersed vegetation is a target for the management of soft-water shallow lakes if they are to meet water quality and biodiversity standards. Knowledge of patterns of macrophyte space occupation and time to recovery is poor and mostly restricted to free floating species or riparian vegetation. Here we use pre- and post-impact monitoring data over 20 years showing the evolution of submersed aquatic vegetation of lake Baciver (Pyrenees), and develop models to infer space occupation and time to recovery. We use pre-impact macrophyte distribution in relation to bathymetry-derived data to fit logistic models to further simulate lake equilibrium scenarios. Depth and slope were found to be the best predictors, and models suggested that an assemblage dominated by Sparganium angustifolium was, at time of this study, over 95% of its potential distribution area. A dense, newly grown monospecific Isoetes lacustris population occupied\10% of its potential area and model projections suggest that it will take decades to recover. An I. lacustris residual population remains below the estimated depth threshold for survival and is bound to disappear. The lake appears to evolve towards a new steady-state where the current lake hypsography promotes the expansion of algae (Nitella sp.) over angiosperms.This study was funded by the Red de Parques Nacionales of the Spanish Ministry of the Environment (PN I?D?I ref. 118/2003 and AQUAREST ref. OAPN 212/2010) and Intramural CSIC (Consejo Superior de Investigaciones Cientı´ficas) ref. 0065.Peer reviewe

Efectos de la actividad ganadera en los lagos del Parque Nacional de Aigüestortes i Estany de Sant Maurici: aportes de nitrógeno y riesgo de eutrofización

Este capítulo contiene 16 páginas, 2 tablas, 11 figuras.El proyecto EGALA estudió el efecto de la actividad ganadera en los lagos del Parque Nacional de Aigüestortes i Estany de Sant Maurici especialmente por los aportes de N que representa y el riesgo de eutrofización que éste puede provocar. La cuestión se planteó a tres escalas espacio-temporales distintas: a escala de paisaje lacustre (en un conjunto de 19 cuencas lacustres) a escala de cuenca lacustre (en un conjunto de 12 lagos de la Vall de Sant Nicolau) y a escala de lago (valorando los efectos a lo largo de un transecto horizontal de la orilla al centro del lago). La concentración de N de los lagos no depende de manera simple de unos pocos factores. Aunque las variables relacionadas con la ganadería explican una fracción marginal de la variancia de las concentraciones de N, no parecen tener un papel significativo en la biogeoquímica de los lagos a escala de paisaje lacustre. Los lagos de mayor altitud con cuencas pequeñas y poco desarrollo de la vegetación y el suelo, acumulan una mayor cantidad de nitrato proveniente del depósito atmosférico. De manera opuesta los lagos situados en el fondo de los valles, con cuencas mayores cubiertas de pastos donde se concentra el ganado, presentan una menor concentración de nitrato en sus aguas, debido a una mayor retención del depósito en los suelos y la vegetación. Aunque la estima de la carga de N que moviliza anualmente la actividad ganadera en las distintas cuencas raramente supera el 20% del depósito atmosférico, se comprobó que es de una magnitud similar a la carga que realmente entra al lago. Esto podría indicar la importancia de la presencia de ganado en la movilización de un N que permanece retenido en la cuenca. Los lagos son sumideros de N, retienen las formas más oxidadas y exportan en menor medida las formas reducidas. El efecto directo de la presencia de ganado es detectable en la orilla del lago, no solo por el impacto físico y la limitación del desarrollo de la comunidad de macrófitos propia del sistema; sino porque se localiza una zona con mayores concentraciones de N, composición isotópica diferenciada y elevadas actividades microbianas. Por dilución y por mezcla con la masa de agua del lago, el efecto se diluye rá- pidamente al aumentar la profundidad de la columna de agua. En este proyecto se han encontrado evidencias de que el ganado tiene influencia sobre el estado trófico de los lagos, y aunque actualmente en general sea baja, se conoce que hay ciertas masas de agua más sensibles y que en tiempos pasados la presencia humana fue mayor y pudo producir un mayor grado de eutrofización de las aguas.El proyecto EGALA ha estado financiado por el Organismo Autónomo Parques Nacionales (nú- mero de referencia 124/2010).Peer reviewe

Uniform temperature profile for a dense array CPV receiver under non uniform illumination profile

Previous experimental and numerical studies of hybrid cooling devices for CPV receivers were developed under uniform illumination profile conditions; but literature review shows that this uniformity assumption is difficult to satisfy in real conditions. This investigation presents the design and the validation of a hybrid cooling device able to tailor its local heat extraction capacity to 2D illumination profiles in order to provide a uniform temperature profile of the PV receiver as well as a low global thermal resistance coefficient. The inputs of the design procedure are the solar concentration, the coolant flow rate and its inlet temperature. As the illumination profile is 2D dependent, a matrix of pin fins is implemented and a hybrid Jet Impingement /Matrix of Pin Fins cooling device is experimentally tested and compared to a hybrid Jet Impingement / Microchannels cooling device developed previously. The results demonstrate similar performances for both designs. Furthermore, in contrast to the cooling scheme using longitudinal fins, the distribution of the pin fins can be tailored, in two dimensions, to the local need of heat extraction capacity.This work is supported by the project ENE2010- 18357 funded by the Spanish Ministry of Science and Innovation (MICINN)

Combined Effects of Leaf Litter Inputs and a Flood on Nutrient Retention in a Mediterranean Mountain Stream During Fall

This study examined the effect of increasing in-channel leaf standing stocks on hydrologic transient storage and nutrient retention in a Mediterranean mountain stream. A flood at the end of the leaf fall period provided the opportunity to examine the effect of abrupt removal of much of the leaf material. Twenty-one chloride additions were performed from October to December 2004. In 13 of these, we also added ammonium and phosphate to estimate nutrient uptake lengths and uptake velocities to assess nutrient retention. The one-dimensional transport with inflow and storage (OTIS) model was used to estimate transient water storage parameters. Although discharge remained constant during leaf fall, water residence time increased because of in-channel litter accumulation, as did nutrient uptake velocity. Flooding reduced leaf benthic standing stocks by 65% and dramatically altered hydraulic and nutrient retention properties of the channel. After recession, the stream rapidly recovered in terms of nutrient retention, especially for phosphate. Abrupt changes in discharge under flood conditions largely determined the variability in stream nutrient retention. However, leaf litter inputs played an important role in nutrient dynamics during constant flow. Because both the flood regime and the timing of leaf fall are being regionally altered by climate change, our results have implications for stream nutrient dynamics under climate change scenarios

A comparative limnological study of the Guadalhorce reservoirs system (Málaga,SE.Spain)

15 páginas ; 6 Figuras ; 2 TablasA partir de 10s muestreos efectuados durante el período de mezcla (marzo de 1988) y estratificación (setiembre de 1988) en 10s tres embalses del sistema Guadalhorce, se analizan sus diferencias fisicoquimicas y biológicas. Aunque 10s tres embalses presentan un contenido de sales disueltas relativamente alto, Conde de Guadalhorce es de aguas carbonatadas, mientras que en Guadalhorce son importantes 10s cloruros y Guadalteba se encuentra en una posición intermedia. En estos dos 61- timos embalses la presencia de cloruros determina la existencia de una haloclina muy marcada, que en el caso de Guadalhorce es permanente. Desde el punto de vista de sus características tróficas, Guadalteba y Guadalhorce son eutróficos, 10 que se refleja en la alta concentración de nutrientes y pigmentos, asi como por tener respiración y ETS elevados. Por el contrario, Conde de Guadalhorce puede considerarse como mesotrófico a partir de 10s mismos parámetros, además de permanecer con oxigeno en el hipolimnion durante todo el verano.This research has been supported by the Comisión Asesora de Investigación Científica y Técnica grant nª PB85-0166 and sponsored by the Dirección General de Obras Hidráulicas of the Ministry of Public AffairsPeer reviewe

Outcomes of COVID-19 Patients Admitted to the Intermediate Respiratory Care Unit: Non-Invasive Respiratory Therapy in a Sequential Protocol

The intermediate respiratory care units (IRCUs) have a pivotal role managing escalation and de-escalation between the general wards and the intensive care units (ICUs). Since the COVID-19 pandemic began, the early detection of patients that could improve on non-invasive respiratory therapies (NRTs) in IRCUs without invasive approaches is crucial to ensure proper medical management and optimize limiting ICU resources. The aim of this study was to assess factors associated with survival, ICU admission and intubation likelihood in COVID-19 patients admitted to IRCUs. Observational retrospective study in consecutive patients admitted to the IRCU of a tertiary hospital from March 2020 to April 2021. Inclusion criteria: hypoxemic respiratory failure (SpO(2) = 25 rpm with FiO(2) > 50% supplementary oxygen) due to acute COVID-19 infection. Demographic, comorbidities, clinical and analytical data, and medical and NRT data were collected at IRCU admission. Multivariate logistic regression models assessed factors associated with survival, ICU admission, and intubation. From 679 patients, 79 patients (12%) had an order to not do intubation. From the remaining 600 (88%), 81% survived, 41% needed ICU admission and 37% required intubation. In the IRCU, 51% required non-invasive ventilation (NIV group) and 49% did not (non-NIV group). Older age and lack of corticosteroid treatment were associated with higher mortality and intubation risk in the scheme, which could be more beneficial in severe forms. Initial NIV does not always mean worse outcomes

Genetic Screening for TLR7 Variants in Young and Previously Healthy Men With Severe COVID-19

Introduction: Loss-of-function TLR7 variants have been recently reported in a small number of males to underlie strong predisposition to severe COVID-19. We aimed to determine the presence of these rare variants in young men with severe COVID-19. Methods: We prospectively studied males between 18 and 50 years-old without predisposing comorbidities that required at least high-flow nasal oxygen to treat COVID-19. The coding region of TLR7 was sequenced to assess the presence of potentially deleterious variants. Results: TLR7 missense variants were identified in two out of 14 patients (14.3%). Overall, the median age was 38 (IQR 30-45) years. Both variants were not previously reported in population control databases and were predicted to be damaging by in silico predictors. In a 30-year-old patient a maternally inherited variant [c.644A>G; p.(Asn215Ser)] was identified, co-segregating in his 27-year-old brother who also contracted severe COVID-19. A second variant [c.2797T>C; p.(Trp933Arg)] was found in a 28-year-old patient, co-segregating in his 24-year-old brother who developed mild COVID-19. Functional testing of this variant revealed decreased type I and II interferon responses in peripheral mononuclear blood cells upon stimulation with the TLR7 agonist imiquimod, confirming a loss-of-function effect. Conclusions: This study supports a rationale for the genetic screening for TLR7 variants in young men with severe COVID-19 in the absence of other relevant risk factors. A diagnosis of TLR7 deficiency could not only inform on treatment options for the patient, but also enables pre-symptomatic testing of at-risk male relatives with the possibility of instituting early preventive and therapeutic interventions

Predictive Factors of Piperacillin Exposure and the Impact on Target Attainment after Continuous Infusion Administration to Critically Ill Patients

Critically ill patients undergo significant pathophysiological changes that affect antibiotic pharmacokinetics. Piperacillin/tazobactam administered by continuous infusion (CI) improves pharmacokinetic/pharmacodynamic (PK/PD) target attainment. This study aimed to characterize piperacillin PK after CI administration of piperacillin/tazobactam in critically ill adult patients with preserved renal function and to determine the empirical optimal dosing regimen. A total of 218 piperacillin concentrations from 106 patients were simultaneously analyzed through the population PK approach. A two-compartment linear model best described the data. Creatinine clearance (CLCR) estimated by CKD-EPI was the covariate, the most predictive factor of piperacillin clearance (CL) interindividual variability. The mean (relative standard error) parameter estimates for the final model were: CL: 12.0 L/h (6.03%); central and peripheral compartment distribution volumes: 20.7 L (8.94%) and 62.4 L (50.80%), respectively; intercompartmental clearance: 4.8 L/h (26.4%). For the PK/PD target of 100% fT(>1xMIC), 12 g of piperacillin provide a probability of target attainment > 90% for MIC 100 mL/min. For 100% fT(>4xMIC), the highest dose (24 g/24 h) was not sufficient to ensure adequate exposure, except for MICs of 1 and 4 mg/L. Our model can be used as a support tool for initial dose guidance and during therapeutic drug monitoring

The global burden attributable to low bone mineral density

Introduction: The Global Burden of Disease Study 2010 estimated the worldwide health burden of 291 diseases and injuries and 67 risk factors by calculating disability-adjusted life years (DALYs). Osteoporosis was not considered as a disease, and bone mineral density (BMD) was analysed as a risk factor for fractures, which formed part of the health burden due to falls. Objectives: To calculate (1) the global distribution of BMD, (2) its population attributable fraction (PAF) for fractures and subsequently for falls, and (3) the number of DALYs due to BMD. Methods: A systematic review was performed seeking population-based studies in which BMD was measured by dual-energy X-ray absorptiometry at the femoral neck in people aged 50 years and over. Age- and sex-specific mean ± SD BMD values (g/cm2) were extracted from eligible studies. Comparative risk assessment methodology was used to calculate PAFs of BMD for fractures. The theoretical minimum risk exposure distribution was estimated as the age- and sex-specific 90th centile from the Third National Health and Nutrition Examination Survey (NHANES III). Relative risks of fractures were obtained from a previous meta-analysis. Hospital data were used to calculate the fraction of the health burden of falls that was due to fractures. Results: Global deaths and DALYs attributable to low BMD increased from 103 000 and 3 125 000 in 1990 to 188 000 and 5 216 000 in 2010, respectively. The percentage of low BMD in the total global burden almost doubled from 1990 (0.12%) to 2010 (0.21%). Around one-third of falls-related deaths were attributable to low BMD. Conclusions: Low BMD is responsible for a growing global health burden, only partially representative of the real burden of osteoporosis