Asociaciones macrobentónicas con presencia de mitílidos de la bahía San Julián (Patagonia austral, Argentina)

The macrobenthic assemblages with mytilids of San Julián bay (Southern Patagonia; Argentina) were sampled in summer 2007 to know its structure; diversity and distribution; and to determine their relationship to different environmental factors. The study was conducted in 3 locations with different types of substrate and slope. Sampling at each site was performed in a transect to cover different levels of intertidal and shallow subtidal. A total of 46 species belonging mainly to molluscs (20); crustaceans (12) and polychaetes (10) were found. Three main macrofaunal assemblages were identified. Platynereis-Clunio- Darina assemblage was distributed in the upper intertidal of muddy and gentle slopes substrate; and had the lowest values of number of species; diversity and abundance of individuals. The Mytilus-Perumytilus assemblage was distributed in the middle and lower intertidal levels in rocky substrate or muddy substrate with abundant support elements and medium slope. This assemblage presented intermediate values of diversity and greater abundance of individuals. The Aulacomya-Exosphaeroma assemblage had the highest number of species and the greatest diversity; but low abundance of individuals; being related to rocky substrate or muddy substrate with support elements and low slopes in the upper subtidal. Species richness and diversity of these assemblages increases from the upper intertidal to subtidal; possibly because of a complex gradient of stress; mainly caused by desiccation and exposure to extreme temperatures.Las asociaciones de macrobentos con presencia de mitílidos de la bahía San Julián (Patagonia austral, Argentina) fueron muestreadas durante el verano de 2007 para conocer su estructura, diversidad y distribución, y para determinar su relación con diversos factores ambientales. El estudio fue realizado en 3 localidades con diferentes tipos de sustrato y distinta pendiente. El muestreo en cada localidad se realizó en una transecta abarcando diferentes niveles del intermareal y del submareal somero. Se hallaron un total de 46 especies pertenecientes principalmente a moluscos (20), crustáceos (12) y poliquetos (10). Se identificaron 3 asociaciones principales: la asociación Platynereis-Clunio-Darina se distribuyó en el nivel intermareal superior de sustrato fangoso y pendientes suaves y presentó los valores más bajos de número de especies, de diversidad específica y de abundancia de individuos; la asociación Mytilus-Perumytilus se distribuyó en los niveles intermareales medio e inferior en sustrato rocoso o en sustrato fangoso con abundantes elementos de soporte y pendiente media; presentó diversidad específica intermedia y la mayor abundancia de individuos; la asociación Aulacomya-Exosphaeroma presentó el mayor número de especies y la mayor diversidad, pero baja abundancia de individuos, encontrándose relacionado a sustratos rocosos o sustratos fangosos con elementos de soporte y baja pendiente del submareal superior. La riqueza específica y la diversidad de estas asociaciones aumentan desde el nivel superior del intermareal hacia el submareal, posiblemente por efecto de un gradiente complejo de estrés, principalmente ocasionado por la desecación y exposición a temperaturas extremas

Spatial changes in the infaunal community of a macrotidal flat in Bahía San Julián, Southern Patagonia, Argentina

The soft-bottom macrobenthos of Bahía San Julián intertidal was surveyed to identify infaunal assemblages and analyze their relationships with the main environmental factors determining species distribution. Four seasonal surveys (summer, autumn, winter and spring) were performed in the middle and lower intertidal levels at seven sampling stations established on both sides of the sewage discharge point, and water and sediment variables were measured. To explore possible spatial variations in the community, environmental and biological data were analyzed using univariate and multivariate statistics. Community composition varied with intertidal level, sediment characteristics and distance to sewage discharge site. In sediment with high mud content, the community was characterized by Darina solenoides, Mysella patagona, Eteone sculpta, Scolecolepides uncinatus and Capitella sp., in the middle intertidal, and was characterized by M. patagona and Ampelisca sp. in the lower intertidal. In sediment with dominance of fine sand, the community was characterized by Aricidea sp. at both intertidal levels. Near the effluent discharge site, the community was largely dominated by M. patagona. Intertidal level and sediment particle size are the main factors determining the composition of benthic assemblages in the study area. Sewage discharge also affects the composition of the infaunal community, possibly as a result of the contribution of particulate organic matter in suspension that stimulates the populations of detritus feeders.El macrobentos intermareal de fondos blandos de Bahía San Julián fue estudiado para identificar las asociaciones infaunales y para analizar su relación con los principales factores ambientales que determinan la distribución de las especies. Se realizaron 4 muestreos estacionales (verano, otoño, invierno y primavera) en los niveles intermareales medio e inferior en 7 estaciones de muestreo establecidas a ambos lados de un sitio de descarga de efluentes urbanos, y se midieron variables del agua y del sedimento. Para explorar las posibles variaciones espaciales en la comunidad, se analizaron los datos ambientales y biológicos utilizando estadística univariada y multivariada. La composición de la comunidad varió con el nivel intermareal, las características del sedimento y la distancia al sitio de descarga de efluentes. En sedimento con alto contenido de fango, la comunidad estuvo caracterizada por Darina solenoides, Mysella patagona, Eteone sculpta, Scolecolepides uncinatus y Capitella sp., en el intermareal medio, y por M. patagona y Ampelisca sp. en el intermareal inferior. En sedimentos con predominio de arena fina, la comunidad estuvo caracterizada por Aricidea sp. en ambos niveles intermareales. Próximo al sitio de descarga de efluentes, la comunidad estuvo ampliamente dominada por M. patagona. El nivel intermareal y el tamaño de partícula del sedimento son los principales factores determinantes de la composición de las asociaciones bentónicas en el área de estudio. El vertido de efluentes también afecta la composición de la comunidad infaunal, posiblemente como resultado del aporte de materia orgánica particulada en suspensión, que estimula a las poblaciones de organismos detritívoros

Ciclo reproductivo y reclutamiento del mejillón Mytilus edulis platensis en Bahía San Julián (Santa Cruz, Argentina)

The purpose of this report is to provide information on the reproductive cycle and recruitment of the mussel Mytilus edulis platensis, a species of commercial importance, in intertidal natural banks of a locality in the province of Santa Cruz. Between 2013 and 2015 biological sampling and seasonal and monthly population censuses of the species were conducted in a natural bank on muddy substrate and in another settled on rocky substrate in the interior of Bahía San Julián. In the laboratory, the total length of the individuals was determined, part of which was then processed by conventional histological techniques to determine the degree of maturity and gonadal development. Monthly zooplankton surveys were also carried out in order to detect the period of greatest concentration of mussel larvae in the water. As a result, a high degree of synchronism was observed in the gonadal maturity stages among individuals of Mytilus edulis platensis in Bahía San Julián; evacuation of gametes occurred from late spring until late summer; the larvae reached their greatest abundance in the plankton during February, when water temperature reached its maximum value; juveniles were incorporated into the population mainly during summer and autumn; abundance of juveniles was generally irregular over time and little predictable in the banks of Bahía San Julián.El presente trabajo tiene por objetivo brindar información sobre el ciclo reproductivo y reclutamiento del mejillón Mytilus edulis platensis, una especie de importancia comercial, en bancos naturales intermareales de una localidad de la Provincia de Santa Cruz. Para ello, entre el 2013 y 2015 se realizaron muestreos biológicos y censos poblacionales estacionales y mensuales de la especie en un banco natural sobre sustrato fangoso y en otro asentado sobre sustrato rocoso en el interior de la Bahía San Julián. En el laboratorio, se determinó el largo total de los individuos, parte de los cuales fue luego procesado mediante técnicas histológicas convencionales para conocer el grado de madurez y desarrollo gonadal. Se realizaron también muestreos mensuales de zooplancton con el fin de detectar la época de mayor concentración de larvas de mejillón en el agua. Como resultado, se observó un alto grado de sincronismo en los estadios de madurez gonadal entre los individuos de Mytilus edulis platensis en la Bahía San Julián; la evacuación de gametas se produjo desde fines de primavera hasta fines de verano; las larvas presentaron su mayor abundancia en el plancton durante el mes de febrero, cuando la temperatura del agua alcanzó su valor máximo; los juveniles se incorporaron a la población principalmente durante el verano y el otoño; la abundancia de juveniles fue generalmente irregular a lo largo del tiempo y poco predecible en los bancos de Bahía San Julián

Asociaciones macrobentónicas con presencia de mitílidos de la bahía San Julián (Patagonia austral, Argentina)

The macrobenthic assemblages with mytilids of San Julián bay (Southern Patagonia, Argentina) were sampled in summer 2007 to know its structure, diversity and distribution, and to determine their relationship to different environmental factors. The study was conducted in 3 locations with different types of substrate and slope. Sampling at each site was performed in a transect to cover different levels of intertidal and shallow subtidal. A total of 46 species belonging mainly to molluscs (20), crustaceans (12) and polychaetes (10) were found. Three main macrofaunal assemblages were identified. Platynereis-Clunio-Darina assemblage was distributed in the upper intertidal of muddy and gentle slopes substrate, and had the lowest values of number of species, diversity and abundance of individuals. The Mytilus-Perumytilus assemblage was distributed in the middle and lower intertidal levels in rocky substrate or muddy substrate with abundant support elements and medium slope. This assemblage presented intermediate values of diversity and greater abundance of individuals. The Aulacomya-Exosphaeroma assemblage had the highest number of species and the greatest diversity, but low abundance of individuals, being related to rocky substrate or muddy substrate with support elements and low slopes in the upper subtidal. Species richness and diversity of these assemblages increases from the upper intertidal to subtidal, possibly because of a complex gradient of stress, mainly caused by desiccation and exposure to extreme temperatures.Las asociaciones de macrobentos con presencia de mitílidos de la bahía San Julián (Patagonia austral, Argentina) fueron muestreadas durante el verano de 2007 para conocer su estructura, diversidad y distribución, y para determinar su relación con diversos factores ambientales. El estudio fue realizado en 3 localidades con diferentes tipos de sustrato y distinta pendiente. El muestreo en cada localidad se realizó en una transecta abarcando diferentes niveles del intermareal y del submareal somero. Se hallaron un total de 46 especies pertenecientes principalmente a moluscos (20), crustáceos (12) y poliquetos (10). Se identificaron 3 asociaciones principales: la asociación Platynereis-Clunio-Darina se distribuyó en el nivel intermareal superior de sustrato fangoso y pendientes suaves y presentó los valores más bajos de número de especies, de diversidad específica y de abundancia de individuos; la asociación Mytilus-Perumytilus se distribuyó en los niveles intermareales medio e inferior en sustrato rocoso o en sustrato fangoso con abundantes elementos de soporte y pendiente media; presentó diversidad específica intermedia y la mayor abundancia de individuos; la asociación Aulacomya-Exosphaeroma presentó el mayor número de especies y la mayor diversidad, pero baja abundancia de individuos, encontrándose relacionado a sustratos rocosos o sustratos fangosos con elementos de soporte y baja pendiente del submareal superior. La riqueza específica y la diversidad de estas asociaciones aumentan desde el nivel superior del intermareal hacia el submareal, posiblemente por efecto de un gradiente complejo de estrés, principalmente ocasionado por la desecación y exposición a temperaturas extremas

Marismas del sur de Santa Cruz, Patagonia austral, Argentina

The coastal zone of southern Patagonia, characterized by a macrotidal regime, allows the development of extensive salt marshes in estuaries and bays, which have been little studied. In order to characterize the marshes of the south of Santa Cruz, identify the main vegetal assemblages and analyze the variations of the vegetal biomass in relation to the tidal level and the time of the year, three samplings were carried out in spring (November 2015), summer (February 2016) and winter (August 2016) in San Julián Bay and the estuaries of the Santa Cruz, Coyle and Gallegos rivers. The samplings were performed using a stratified random design, dividing the salt marsh into three levels: high, middle and low. Six samples of 0.25 m2 were collected at each level, and the percentage of coverage of each species and its aerial biomass (dry weight) was determined. Substrate grain size and organic matter content of the sediment (%) were also determined. The data were analyzed by factorial ANOVA (locality, level, and season of the year). The substrate in all localities and levels consisted mainly of silt-clays (54 to 88%) and fine sand(20 to 44%). Organic matter content varied between 4.5 and 7.1%. Five plant species were recorded: Sarcocornia perennis, Puccinellia glaucescens, Suaeda argentinensis, Limonium brasiliense and Spartina sp. S. perennis was the dominant species in almost all localities and levels, with the exception of the high and the middle salt marsh of San Julián Bay, where it codominates with Limonium brasiliense, and the low marsh of the estuary of the Santa Cruz River, where it codominates together with Spartina sp. The total aerial vegetation biomass reached its maximum value (1700 g m-2) during the summer in the low marsh of the estuary of the Gallegos river; all the biomass corresponded to S. perennis. The lowest value of total biomass (177 g m-2) was recorded in the high marsh of San Julián Bay during the winter and corresponded in 33.8% to S. perennis. The coverage of S. perennis varied between 23 and 100%, being always higher in the low marsh. Spartina sp. was found only in the low marsh of the estuary of the Santa Cruz River,site that constitutes the southernmost record for this halophyte on the Argentina coast.La zona costera de la Patagonia austral, caracterizada por un régimen macromareal, permite el desarrollo de extensas marismas tanto en estuarios como en bahías, que han sido muy poco estudiadas. Con el objetivo de caracterizar las marismas del sur de Santa Cruz, identificar las principales asociaciones vegetales que las componen y analizar las variaciones de la biomasa vegetal en relación al nivel de marea y la época del año, se realizaron muestreos en primavera (noviembre 2015), verano (febrero 2016) e invierno (agosto de 2016) en la bahía San Julián y los estuarios de los ríos Santa Cruz, Coyle y Gallegos. Los muestreos se realizaron empleando un diseño aleatorio estratificado, dividiendo la marisma en tres niveles: alta, media y baja. Se recolectaron seis muestras de 0,25 m2 en cada nivel y se determinó el porcentaje de cobertura de cada especie y su biomasa aérea (peso seco). Se determinó también la granulometría y la materia orgánica del sedimento (%). Los datos se analizaron mediante ANOVA factorial (sitios, nivel, estación del año). El sustrato en todas las localidades y niveles estuvo constituido principalmente por limos-arcillas (54 a 88%) y arena fina(20 a 44%). La materia orgánica varió entre 4,5 y 7,1%. Se registraron cinco especies vegetales: Sarcocornia perennis, Puccinellia glaucescens, Suaeda argentinensis, Limonium brasiliense y Spartina sp. S.perennis fue la especie dominante en casi todos los sitios y niveles, con excepción de la marisma alta y la marisma media de Bahía San Julián, donde codomina junto a Limonium brasiliense, y la marisma baja del estuario del río Santa Cruz, donde codomina junto a Spartinasp. La biomasa vegetal aérea total alcanzó su valor máximo (1700 g m-2) durante el verano en la marisma baja del estuario del río Gallegos y correspondió en su totalidad a S.perennis. El valor más bajo de biomasa total (177 g m-2) fue registrado en la marisma alta de Bahía San Julián durante el invierno y correspondió en un 33,8% a S. perennis. La cobertura de S. perennis varió entre 23 y 100%, siendo siempre mayor en la marisma baja. Spartina sp. se encontró únicamente en la marisma baja del estuario del río Santa Cruz, sitio que constituye el registro más austral para esta halófita en la costa Argentina

Respiratory support in patients with severe COVID-19 in the International Severe Acute Respiratory and Emerging Infection (ISARIC) COVID-19 study: a prospective, multinational, observational study

Background: Up to 30% of hospitalised patients with COVID-19 require advanced respiratory support, including high-flow nasal cannulas (HFNC), non-invasive mechanical ventilation (NIV), or invasive mechanical ventilation (IMV). We aimed to describe the clinical characteristics, outcomes and risk factors for failing non-invasive respiratory support in patients treated with severe COVID-19 during the first two years of the pandemic in high-income countries (HICs) and low middle-income countries (LMICs). Methods: This is a multinational, multicentre, prospective cohort study embedded in the ISARIC-WHO COVID-19 Clinical Characterisation Protocol. Patients with laboratory-confirmed SARS-CoV-2 infection who required hospital admission were recruited prospectively. Patients treated with HFNC, NIV, or IMV within the first 24 h of hospital admission were included in this study. Descriptive statistics, random forest, and logistic regression analyses were used to describe clinical characteristics and compare clinical outcomes among patients treated with the different types of advanced respiratory support. Results: A total of 66,565 patients were included in this study. Overall, 82.6% of patients were treated in HIC, and 40.6% were admitted to the hospital during the first pandemic wave. During the first 24 h after hospital admission, patients in HICs were more frequently treated with HFNC (48.0%), followed by NIV (38.6%) and IMV (13.4%). In contrast, patients admitted in lower- and middle-income countries (LMICs) were less frequently treated with HFNC (16.1%) and the majority received IMV (59.1%). The failure rate of non-invasive respiratory support (i.e. HFNC or NIV) was 15.5%, of which 71.2% were from HIC and 28.8% from LMIC. The variables most strongly associated with non-invasive ventilation failure, defined as progression to IMV, were high leukocyte counts at hospital admission (OR [95%CI]; 5.86 [4.83–7.10]), treatment in an LMIC (OR [95%CI]; 2.04 [1.97–2.11]), and tachypnoea at hospital admission (OR [95%CI]; 1.16 [1.14–1.18]). Patients who failed HFNC/NIV had a higher 28-day fatality ratio (OR [95%CI]; 1.27 [1.25–1.30]). Conclusions: In the present international cohort, the most frequently used advanced respiratory support was the HFNC. However, IMV was used more often in LMIC. Higher leucocyte count, tachypnoea, and treatment in LMIC were risk factors for HFNC/NIV failure. HFNC/NIV failure was related to worse clinical outcomes, such as 28-day mortality. Trial registration This is a prospective observational study; therefore, no health care interventions were applied to participants, and trial registration is not applicable

The value of open-source clinical science in pandemic response: lessons from ISARIC

International audienc