Écologie et performance photosynthétique du phytoplancton pendant un cycle de marée vive-eau/morte-eau, dans le front du sud du golfe San Jorge, Patagonie

RÉSUMÉ: Les fronts de marées sont des interfaces qui séparent les eaux stratifiées plus profondes des eaux mélangées moins profondes, où les courants de marée fournissent l’énergie turbulente pour mélanger la colonne d’eau et qui peuvent vaincre la pycnocline dans les zones moins profondes. La zone stratifiée présente des concentrations en nutriments plus faibles dans la couche de surface que dans la zone mélangée. On s’attend donc à trouver différents assemblages de phytoplancton entre la zone mélangée et la zone stratifiée du front. Le front du sud du Golfe San Jorge, en Argentine, a été étudié pendant un cycle de marée de vive-eau/morte-eau, en considérant les gradients horizontaux de densité, les courants de marées et la bathymétrie. La position et la forme du front sont influencées par des instabilités baroclines, qui jouent probablement un rôle dans le transport horizontal de nutriments à travers le front. Le phytoplancton a été classifié de la manière suivante : micro-phytoplancton (diatomées et dinoflagellés), nano-phytoplancton, pico- phytoplancton et cyanobactéries. Les hétérotrophes ont été classifiés comme suit: dinoflagellés (hétérotrophes et mixotrophes), ciliés et bactéries. La plus forte concentration de biomasse phytoplanctonique a été trouvée du côté stratifié pendant la marée de morte- eau, où les groupes phytoplanctoniques les plus petits, composés de pico- et nano- phytoplancton et cyanobactéries, apportent la plus grande contribution de carbone à la biomasse totale. La biomasse hétérotrophique la plus importante est apportée par les bactéries. Pendant la marée de vive-eau, dans la zone stratifiée, la plus grande contribution de carbone est apportée par les cellules micro-phytoplanctoniques : dinoflagellés et diatomées. Le carbone des hétérotrophes est principalement apporté par les grands cellules comme les ciliés et les dinoflagellés. La zone mélangée montre des résultats remarquables par rapport à l’état physiologique des cellules, qui présentent une photo-acclimatation de leur système photosyntétique aux conditions optimales moyenne de lumière. Ce résultat suggère que les cellules proches de la surface sont probablement photo-inhibées, et que les cellules sous la zone euphotique, moins lumineuse, sont advectées par les mouvements turbulents verticaux à des profondeurs où les conditions de lumière sont optimales. -- Mot(s) clé(s) en français : front de marées, marée vive-eau, marée morte eau, densité, zone mélangée, zone stratifiée, transport des nutriments, phytoplancton, biomasse, états physiologique. -- ABSTRACT: Tidal fronts are interfaces separating stratified deepest waters from the mixed shallowest waters, where tidal currents provide enough turbulent energy to mix the entire water column and to overcome stratification in shallow zones. The stratified side is characterized by lower inorganic nutrients concentrations in the surface layer than the mixed side. Therefore, phytoplankton assemblages are expected to be quantitatively or qualitatively different from one side to the other of the front. The front presents in the south of San Jorge Gulf (SJG), Argentina, was characterized during a spring-neap tidal cycle considering horizontal gradients of density, tidal currents and bathymetry. It was found that baroclinic instabilities influence the shape and position of the front and presumable play a role in the horizontal nutrient transport across the front. The phytoplankton was categorized as: microphytoplankton (diatoms and dinoflagellates), nanophytoplankton, picophytoplankton and cyanobacteria. The heterotrophes were categorized as: dinoflagellates (heterotrophes and mixotrophes), ciliates and bacterias. The highest phytoplankton biomass concentrations were found in the stratified side of the front during neap tide. Under such conditions, the main contributors to the total autotrophic biomass were the smallest size groups as pico-phytoplankton and cyanobacteria and nanophytoplankton. The main contribution to heterotrophic biomass was mainly bacteria. On the other hand, the stratified side during spring tide showed a higher contribution of carbon from bigger microphytolankton cells than during neap tide, corresponding to dinoflagellates and diatoms. This side of the front presented the largest heterotrophic cells, such as ciliates and heterotrophic dinoflagellates. The mixed side is not less important, as shown by the physiological state of autotrophes. Indeed, cells present in well-mixed waters photo-acclimate their photosynthetic system to an optimum of light conditions, suggesting that cells near the surface, which are probably photo-inhibited, and cells below the euphotic zone, which are light-deprived, are quickly advected by turbulent vertical motions to the depth range with optimal irradiance conditions. -- Mot(s) clé(s) en anglais : tidal front, spring tide, neap tide, density, mixed side, stratified side, nutrients transport, phytoplankton, biomass, physiological state

Phytoplankton ecology during a spring-neap tidal cycle in the southern tidal front of san jorge gulf, patagonia

Tidal fronts are interfaces that separate stratified from mixed waters. The stratified surface zone of a front has lower inorganic nutrient concentrations than the mixed side, and thus, phytoplankton assemblages are expected to differ from one side of the front to the other. Here, we characterize the physics, nutrient dynamics, and biology of the southern front in San Jorge Gulf (SJG), Argentina, during a spring-neap tidal cycle. Baroclinic instabilities influence the shape and position of the front and presumably play an important role in the horizontal transport across the front. The highest phytoplankton biomass concentrations were found in the waters of the stratified side of the front during neap tide, with picophytoplankton, cyanobacteria, and nanophyto-plankton being the main contributors to the total autotrophic biomass. Bacteria contribute the most to heterotrophic biomass. In contrast, during spring tide, the carbon contribution of microphytoplankton was higher than during neap tide. In the mixed side, cells photoacclimate to optimum light conditions, suggesting that cells near the surface, which are probably photoinhibited, and cells below the euphotic zone, which are light-limited, are quickly advected by turbulent vertical motions to depths with optimal irradiance conditions.Fil: Flores Melo, Elizabeth Ximena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Institut des Sciences de la Mer de Rimouski; CanadáFil: Schloss, Irene Ruth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; Argentina. Institut des Sciences de la Mer de Rimouski; CanadáFil: Chavanne, Cédric. Institut des Sciences de la Mer de Rimouski; CanadáFil: Almandoz, Gaston Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Facultad de Ciencias Naturales y Museo, Universidad Nacional de la Plata; ArgentinaFil: Latorre, Maite Pilmayquen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Ferreyra, Gustavo Adolfo. Institut des Sciences de la Mer de Rimouski; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Phytoplankton Ecology During a Spring-Neap Tidal Cycle in the Southern Tidal Front of San Jorge Gulf, Patagonia

Tidal fronts are interfaces that separate stratified from mixed waters. The stratified surface zone of a front has lower inorganic nutrient concentrations than the mixed side, and thus, phytoplankton assemblages are expected to differ from one side of the front to the other. Here, we characterize the physics, nutrient dynamics, and biology of the southern front in San Jorge Gulf (SJG), Argentina, during a spring-neap tidal cycle. Baroclinic instabilities influence the shape and position of the front and presumably play an important role in the horizontal transport across the front. The highest phytoplankton biomass concentrations were found in the waters of the stratified side of the front during neap tide, with picophytoplankton, cyanobacteria, and nanophyto-plankton being the main contributors to the total autotrophic biomass. Bacteria contribute the most to heterotrophic biomass. In contrast, during spring tide, the carbon contribution of microphytoplankton was higher than during neap tide. In the mixed side, cells photoacclimate to optimum light conditions, suggesting that cells near the surface, which are probably photoinhibited, and cells below the euphotic zone, which are light-limited, are quickly advected by turbulent vertical motions to depths with optimal irradiance conditions.Facultad de Ciencias Naturales y Muse

Cianobacterias ácido-termófilas del complejo termal copahue, Neuquén, Argentina

El objetivo de este trabajo fue identificar las especies de cianobacterias ácido-termófilas que, junto con las aguas, microalgas y fangos, son importantes recursos termales utilizados con fines terapéuticos en el Complejo Termal Copahue. El trabajo presenta descripciones, comentarios e ilustraciones de las 11 especies identificadas pertenecientes a nueve géneros: Chroococcidiopsis, Chroococcus, Kamptonema, Komvophoron, Leptolyngbya, Mastigocladus, Oscillatoria, Phormidium y Spirulina recolectadas en diez sitios de muestreo. Cinco especies: Chroococcus membraninus, Chroococcidiopsis thermalis, Spirulina gracilis, Phormidium thermobium y Komvophoron jovis, son citadas por primera vez para la Argentina. Además, se aislaron y mantuvieron en cultivo unialgal cuatro especies: Chroococcus membraninus, Chroococcidiopsis thermalis, Kamptonema animale y Mastigocladus laminosus. M. laminosus resultó ser la especie encontrada con mayor frecuencia en el área, ya que se la registró en ocho de los diez sitios. La Laguna Los Callos fue el sitio con mayor diversidad, donde se registró el mayor número de especies, ocho en total. Todas las especies de cianobacterias estudiadas en el presente trabajo son utilizadas, ya sea mediante la aplicación directa de las matas o por la utilización de sus componentes activos, en las aguas y en los fangosThe objective of this work was to identify the species of acid-thermophilic cyanobacteria which,together with the waters, microalgae and mud, are important thermal resources used for therapeuticpurposes in the Copahue Thermal Complex. The work presents descriptions, comments, and illustrationsof the 11 identified species belonging to nine genera: Chroococcidiopsis, Chroococcus, Kamptonema,Komvophoron, Leptolyngbya, Mastigocladus, Oscillatoria, Phormidium and Spirulina, collected inten sampling sites. Five species: Chroococcus membraninus, Chroococcidiopsis thermalis, Spirulinagracilis, Phormidium thermobium, and Komvophoron jovis, are cited for the first time for Argentina. In addition, four species were isolated and maintained in unialgal culture: Chroococcus membraninus, Chroococcidiopsis thermalis, Kamptonema animale and Mastigocladus laminosus. M. laminosus was the most frequently encountered species of the area, since it was found in eight of the ten sites. The Laguna Los Callos was the most diverse site, with the largest number of species, eight in total. All the species of cyanobacteria studied in the present work are used, either through the direct application of themats or through the use of their active components in water, and mud.Fil: Flores Melo, Elizabeth Ximena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: de la Rosa, Iris Nadia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Wenzel, Maria Teresa. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Diaz, Monica Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin

Mixing processes at the pycnocline and vertical nitrate supply: consequences for the microbial food web in San Jorge Gulf, Argentina

Little is known about the base of the food web that could support the high productivity and marine biodiversity found in San Jorge Gulf, Patagonia, Argentina. Here we examine the key components of the microbial food web, including the standing stock and physiological state of the phytoplankton in the context of key oceanographic variables in the gulf. Water samples were collected at 16 stations for biological and chemical analyses, together with measurements of vertical structure and currents. The dynamics of the water column and its impact on nutrient availability for primary producers was evaluated. Our results show that, in spite of the observed low surface nutrient concentrations and low biomass, phytoplankton cells were in good physiological state. This is possible because nutrients are replenished at the pycnocline depth, as estimated by means of Richardson’s dynamic stability. Turbulence created by tides and the shear between overlapping water masses favors the disruption of the pycnocline. We suggest that, during summer, San Jorge Gulf maintains not only high primary productivity but also high phytoplankton biomass turnover rate, which is supported by a high C:N ratio, consistent with strong zooplankton grazing and export of organic carbon to deep waters.Facultad de Ciencias Naturales y Muse

Particle dynamics in Ushuaia Bay (Tierra del Fuego)-Potential effect on dissolved oxygen depletion

This study examines the distribution and seasonal evolution of hydrographic, hydrodynamic, and nepheloid layers in Ushuaia Bay and the submerged glacial valley that connects it to the Beagle Channel. The hydrographic structure is highly seasonal, with a total mixing of the water column in winter and the appearance of a pycnocline between 50 and 70 m deep from spring to late autumn, mainly due to desalination. A counter-clockwise current sweeps the entire bay regardless of the season or phase of the tide. This current is at its maximum in the surface layer, allowing the rapid renewal of the bay's waters, while deep currents are weak and imply a slow renewal of the valley's waters. Turbid and oxygen-depleted structures are observed in summer in the valley. The combination of seasonal stratification, high organic matter inputs from planktonic production, oxygen consumption for remineralization, and sluggish circulation results in a decrease in near-bottom oxygen concentration in the glacial valley at the end of the stratified season, before mixing and re-oxygenation of the water column during the southern winter. The possible impact of dissolved oxygen depletion in the bottom waters of the valley on benthic organisms, like crustaceans, is discussed.Fil: Flores Melo, Elizabeth Ximena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Martín de Nascimento, Jacobo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Kerdel, Lounes. Centre National de la Recherche Scientifique; FranciaFil: François, Bourrin. Centre National de la Recherche Scientifique; FranciaFil: Colloca, Cristina Beatriz. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; ArgentinaFil: Menniti, Chirstophe. Centre National de la Recherche Scientifique; FranciaFil: Durrieu de Madron, Xavier. Centre National de la Recherche Scientifique; Franci

Mixing processes at the pycnocline and vertical nitrate supply: Consequences for the microbial food web in San Jorge Gulf, Argentina

Little is known about the base of the food web that could support the high productivity and marine biodiversity found in San Jorge Gulf, Patagonia, Argentina. Here we examine the key components of the microbial food web, including the standing stock and physiological state of the phytoplankton in the context of key oceanographic variables in the gulf. Water samples were collected at 16 stations for biological and chemical analyses, together with measurements of vertical structure and currents. The dynamics of the water column and its impact on nutrient availability for primary producers was evaluated. Our results show that, in spite of the observed low surface nutrient concentrations and low biomass, phytoplankton cells were in good physiological state. This is possible because nutrients are replenished at the pycnocline depth, as estimated by means of Richardson’s dynamic stability. Turbulence created by tides and the shear between overlapping water masses favors the disruption of the pycnocline. We suggest that, during summer, San Jorge Gulf maintains not only high primary productivity but also high phytoplankton biomass turnover rate, which is supported by a high C:N ratio, consistent with strong zooplankton grazing and export of organic carbon to deep waters.Fil: Latorre, Maite Pilmayquen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Schloss, Irene Ruth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Almandoz, Gaston Osvaldo. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lemarchand, Karine. Université du Québec à Rimouski; CanadáFil: Flores Melo, Elizabeth Ximena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Massé Beaulne, Valérie. Maurice Lamontagne Institute; CanadáFil: Ferreyra, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Université du Québec à Rimouski; Canad

Caracterización limnológica del agua, las algas y los barros utilizados en el Complejo Termal Copahue (Neuquén, Argentina)

We carried out the physicochemical characterization of extreme environments of acidic geothermal springs of the Copahue Thermal Complex, and isolated and cultivated algae used for therapeutic and medicinal purposes. Ecophysiological aspects, algal photosynthetic responses and potential toxicity of sediments were analysed. At the 15 sampling sites (pH: 2.0-6.7, conductivity: 283-3230 µS/cm, temperature: 22-60°C), 11 Cyanobacteria species of a total of 24 algae were identified. The species richness was low with true inhabitants of highly acidic waters: Cyanidium caldarium, Euglena mutabilis, Chlamydomonas acidophila, Achnanthidium minutissimum, and Eunotia exigua, and cosmopolitan species of thermal springs: Mastigocladus laminosus, Leptolyngbia boryana and Phormidium tergestinum. All the species were well adapted to low light levels (15-55 µmol photon.m-2.s-1), and photosynthetic responses were similar to those in comparable environments. pH and temperature were important factors in algal distribution, and N:P relationship suggests that P is the limiting nutrient for algal growth. Fractions controlling P availability in the muds were those bound to organic matter, and Fe/Al oxyhydroxides. Healing muds have the ability to precipitate metals and would not be toxic. Cadmium and other potentially toxic metals were in very low concentrations and pose no risk for the human use as healing muds and bathing.Se realizó la caracterización físico-química de los ambientes extremos (aguas termales y barros) del Complejo Termal Copahue, y se aislaron y cultivaron algas empleadas con propósitos medicinales y terapéuticos. Se analizaron aspectos ecofisiológicos de las especies y sus respuestas fotosintéticas, así como la potencial toxicidad de los barros. En los 15 sitios muestreados (pH: 2.0-6.7, conductividad: 283-3230 µS/cm, temperatura: 22-60 °C) se identificaron 11 especies de cianobacterias de un total de 24 especies algales. La riqueza específica fue baja, con especies representativas de ambientes ácidos: Cyanidium caldarium, Euglena mutabilis, Chlamydomonas acidophila, Achnanthidium minutissimum y Eunotia exigua, y especies cosmopolitas de aguas termales: Mastigocladus laminosus, Leptolyngbia boryana y Phormidium tergestinum. Todas las especies mostraron estar bien adaptadas a bajas intensidades lumínicas (15-55 µmol fotones.m-2.s-1) y sus respuestas fotosintéticas resultaron comparables a las de ambientes similares. El pH y la temperatura fueron factores importantes en la distribución de las algas, y la alta relación N:P sugiere que el P es el nutriente limitante del crecimiento algal. Las fracciones que controlaron la disponibilidad de P en los sedimentos fueron las de materia orgánica y de oxihidróxidos de Fe/Al. Los barros terapéuticos mostraron capacidad para precipitar los metales y no serían tóxicos. El Cd y otros metales potencialmente tóxicos estuvieron presentes en muy bajas concentraciones y no representarían un riesgo para uso humano como barros curativos y baños.Fil: Flores Melo, Elizabeth Ximena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: de la Rosa, Iris Nadia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Baffico, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Temporetti, Pedro Felix. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Wenzel, María T.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Cabrera, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Pedrozo, Fernando Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Diaz, Monica Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin

General Hydrography of the Beagle Channel, a Subantarctic Interoceanic Passage at the Southern Tip of South America

The Beagle Channel (BC) is a long and narrow interoceanic passage (∼270 km long and 1–12 km wide) with west-east orientation and complex bathymetry connecting the Pacific and Atlantic oceans at latitude 55°S. This study is the first integrated assessment of the main oceanographic features of the BC, using recent oceanographic observations from cruises, moored instruments and historical observations. The waters transported into the BC are supplied mainly by the Cape Horn Current, which carries Subantarctic Water (SAAW) at depth (100 m below surface) along the Pacific Patagonian continental shelf break. SAAW enters the continental shelf via a submarine canyon at the western entrance of the BC. The SAAW is diluted by fresh, nutrient depleted (nitrate, phosphate and silicic acid) Estuarine Water (EW) from Cordillera Darwin Ice Field (CDIF) forming modified SAAW (mSAAW). Freshwater inputs from the CDIF generate a two-layer system with a sharp pycnocline which delimits the vertical distribution of phytoplankton fluorescence (PF). Two shallow sills (<70 m) along the BC contribute to EW and mSAAW mixing and the homogenization of the entire water column east of the sills, coherent with Bernoulli aspiration. The central section of the BC, extending ∼100 km toward the east, is filled by a salty (31–32) variety of EW. In winter, this central section is nearly vertically homogeneous with low nutrient concentrations (0.9–1.1 μM PO4 and 7.5–10 μM NO3) and PF. The temporal variability of seawater temperature from 50 to 195 m in the central section of the BC was found to be mostly dominated by the annual and semiannual cycles and influenced by tidal forcing. The middle section of the BC was less influenced by oceanic inputs and its basin-like structure most likely favors retention, which was observed from the weakly stratified water column at the mooring site. Toward the east, the central section bathymetry is disrupted at Mackinlay Strait where another shallow sill separates the middle channel from the shallow eastern entrance that connects to the Atlantic Ocean. In this section, a weakly stratified two-layer system is formed when the eastward surface outflow (salty-EW) flows over a deeper, denser tongue of oceanic mSAAW.Fil: Giesecke Astorga, Claudio Ricardo. Universidad Austral de Chile; ChileFil: Martín de Nascimento, Jacobo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego, Antártida e Islas del Atlántico Sur. Instituto de Ciencias Polares, Ambientales y Recursos Naturales; ArgentinaFil: Piñones, Andrea. Universidad Austral de Chile; ChileFil: Höfer, Juan. Pontificia Universidad Católica de Valparaíso; ChileFil: Garcés Vargas, Jose. Universidad Austral de Chile; ChileFil: Flores Melo, Elizabeth Ximena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Alarcón, Emilio. Universidad Austral de Chile; ChileFil: Durrieu de Madron, Xavier. Centre National de la Recherche Scientifique; FranciaFil: Bourrin, François. Centre National de la Recherche Scientifique; FranciaFil: González, Humberto E.. Universidad Austral de Chile; Chil

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030