Quantifying bioirrigation using ecological parameters: a stochastic approach†

Irrigation by benthic macrofauna has a major influence on the biogeochemistry and microbial community structure of sediments. Existing quantitative models of bioirrigation rely primarily on chemical, rather than ecological, information and the depth-dependence of bioirrigation intensity is either imposed or constrained through a data fitting procedure. In this study, stochastic simulations of 3D burrow networks are used to calculate mean densities, volumes and wall surface areas of burrows, as well as their variabilities, as a function of sediment depth. Burrow networks of the following model organisms are considered: the polychaete worms Nereis diversicolor and Schizocardium sp., the shrimp Callianassa subterranea, the echiuran worm Maxmuelleria lankesteri, the fiddler crabs Uca minax, U. pugnax and U. pugilator, and the mud crabs Sesarma reticulatum and Eurytium limosum. Consortia of these model organisms are then used to predict burrow networks in a shallow water carbonate sediment at Dry Tortugas, FL, and in two intertidal saltmarsh sites at Sapelo Island, GA. Solute-specific nonlocal bioirrigation coefficients are calculated from the depth-dependent burrow surface areas and the radial diffusive length scale around the burrows. Bioirrigation coefficients for sulfate obtained from network simulations, with the diffusive length scales constrained by sulfate reduction rate profiles, agree with independent estimates of bioirrigation coefficients based on pore water chemistry. Bioirrigation coefficients for O(2 )derived from the stochastic model, with the diffusion length scales constrained by O(2 )microprofiles measured at the sediment/water interface, are larger than irrigation coefficients based on vertical pore water chemical profiles. This reflects, in part, the rapid attenuation with depth of the O(2 )concentration within the burrows, which reduces the driving force for chemical transfer across the burrow walls. Correction for the depletion of O(2 )in the burrows results in closer agreement between stochastically-derived and chemically-derived irrigation coefficient profiles

Discerning natural and anthropogenic organic matter inputs to salt marsh sediments of Ria Formosa lagoon (South Portugal)

Sedimentary organic matter (OM) origin and molecular composition provide useful information to understand carbon cycling in coastal wetlands. Core sediments from threors' Contributionse transects along Ria Formosa lagoon intertidal zone were analysed using analytical pyrolysis (Py-GC/MS) to determine composition, distribution and origin of sedimentary OM. The distribution of alkyl compounds (alkanes, alkanoic acids and alkan-2-ones), polycyclic aromatic hydrocarbons (PAHs), lignin-derived methoxyphenols, linear alkylbenzenes (LABs), steranes and hopanes indicated OM inputs to the intertidal environment from natural-autochthonous and allochthonous-as well as anthropogenic. Several n-alkane geochemical indices used to assess the distribution of main OM sources (terrestrial and marine) in the sediments indicate that algal and aquatic macrophyte derived OM inputs dominated over terrigenous plant sources. The lignin-derived methoxyphenol assemblage, dominated by vinylguaiacol and vinylsyringol derivatives in all sediments, points to large OM contribution from higher plants. The spatial distributions of PAHs (polyaromatic hydrocarbons) showed that most pollution sources were mixed sources including both pyrogenic and petrogenic. Low carbon preference indexes (CPI > 1) for n-alkanes, the presence of UCM (unresolved complex mixture) and the distribution of hopanes (C-29-C-36) and steranes (C-27-C-29) suggested localized petroleum-derived hydrocarbon inputs to the core sediments. Series of LABs were found in most sediment samples also pointing to domestic sewage anthropogenic contributions to the sediment OM.EU Erasmus Mundus Joint Doctorate fellowship (FUECA, University of Cadiz, Spain)EUEuropean Commission [FP7-ENV-2011, 282845, FP7-534 ENV-2012, 308392]MINECO project INTERCARBON [CGL2016-78937-R]info:eu-repo/semantics/publishedVersio

Unique archaeal assemblages in the Arctic Ocean unveiled by massively parallel tag sequencing

10 páginas, 4 figuras, 1 tabla.The Arctic Ocean plays a critical role in controlling nutrient budgets between the Pacific and Atlantic Ocean. Archaea are key players in the nitrogen cycle and in cycling nutrients, but their community composition has been little studied in the Arctic Ocean. Here, we characterize archaeal assemblages from surface and deep Arctic water masses using massively parallel tag sequencing of the V6 region of the 16S rRNA gene. This approach gave a very high coverage of the natural communities, allowing a precise description of archaeal assemblages. This first taxonomic description of archaeal communities by tag sequencing reported so far shows that it is possible to assign an identity below phylum level to most (95%) of the archaeal V6 tags, and shows that tag sequencing is a powerful tool for resolving the diversity and distribution of specific microbes in the environment. Marine group I Crenarchaeota was overall the most abundant group in the Arctic Ocean and comprised between 27% and 63% of all tags. Group III Euryarchaeota were more abundant in deep-water masses and represented the largest archaeal group in the deep Atlantic layer of the central Arctic Ocean. Coastal surface waters, in turn, harbored more group II Euryarchaeota. Moreover, group II sequences that dominated surface waters were different from the group II sequences detected in deep waters, suggesting functional differences in closely related groups. Our results unveiled for the first time an archaeal community dominated by group III Euryarchaeota and show biogeographical traits for marine Arctic Archaea.P E Galand is supported by a Marie Curie grant (CRENARC MEIF-CT-2007–040247). EO Casamayor was supported by a Spanish grant CGL2006–12058-BOS, and D L Kirchman by NSF OPP ARC-0632233. C Lovejoy would like to acknowledge the support of the Natural Sciences and Engineering Council, Canada (NSERC) Special Research Opportunity Fund. We thank C Pedros-Alio for support during CASES. Deep Arctic samples were collected by K Scarcella and E Didierjean, and we thank the Chief Scientist, Officers and Crew of the CCGS Louis St Laurent and support from Fisheries and Oceans Canada. Tag sequencing was supported by a Keck foundation grant to M Sogin and L Ameral Zettler. This is a contribution to the International Census of Marine Microbes (ICOMM).Peer reviewe

Percepciones de continuidad de la atención por parte de los usuarios de los sistemas de salud en Colombia y Brasil: M Luisa Vázquez

Antecedentes La continuidad de la atención (CC) es el grado en que el paciente experimenta la atención con el tiempo como coherente y vinculada. Se identifican tres tipos de CC: relacional, informativo y gerencial. El objetivo es determinar el grado de continuidad de la atención entre la atención primaria (PC) y la atención secundaria (SC) e identificar los factores asociados en Brasil y Colombia, países con diferentes sistemas de salud. Métodos Estudio transversal mediante una encuesta de población en Brasil (Pernambuco, n = 465) y Colombia (Bogotá, n = 609) en 2011. Se analizaron los usuarios de los servicios de salud de los sistemas de salud pública de cada país. Variables de resultado: índices sintéticos en CC relacional, informativo y gerencial. Variables explicativas: características sociodemográficas y salud. Se realizaron análisis descriptivos y modelos de regresión logística multivariante. Resultados El CC relacional fue mayor en Brasil que en Colombia tanto para los médicos de PC (82.2 y 72.9%, respectivamente) como para los médicos de SC (82.4 y 70.1%, respectivamente), pero la percepción de una buena transferencia de información (CC informativo) es menor (56.3 y 67.6%, respectivamente). No se encontraron diferencias en la percepción de consistencia de la atención (CC gerencial) (alrededor del 70%). Entre los factores asociados con CC, se destacan los siguientes: en Brasil, la edad (ancianos) y el área (Caruaru, ciudad remota) se asociaron con cualquier tipo de CC. En ambos países, la mala salud autoevaluada se asoció con niveles más bajos de CC relacional y en Colombia, también, con el control clínico CC. Además, en Colombia, Conclusiones El nivel de continuidad relacional y gerencial percibida es alto, y de continuidad informativa, baja. Los factores asociados con la percepción de la continuidad de la atención difieren según el país y el tipo de continuidad de la atención. Mensajes clave Es el primer intento de evaluar los tres tipos de continuidad de la atención en áreas de Colombia y Brasil. La comprensión de los factores asociados con la continuidad de la atención revelará qué aspectos del sistema de salud pública podrían mejorarse.Background Continuity of care (CC) is the degree to which the patient experiences care over time as coherent and linked. Three types of CC are identified: relational, informational and managerial. The aim is to determine the degree of continuity of care between primary (PC) and secondary care (SC) and to identify the associated factors in Brazil and Colombia, countries with different health systems. Methods Cross-sectional study by means of a population survey in Brazil (Pernambuco, n = 465) and Colombia (Bogota, n = 609) in 2011. Users of health services of public health systems of each country were analyzed. Outcome variables: synthetic indexes on relational, informational and managerial CC. Explanatory variables: sociodemographic characteristics and health. Descriptive analysis and multivariate logistic regression models were performed. Results Relational CC was higher in Brazil than in Colombia both for PC physicians (82.2 and 72.9%, respectively) and for SC physicians (82.4 and 70.1%, respectively), but the perception of a good information transfer (informational CC) is lower (56.3 and 67.6%, respectively). No differences in the perception of consistency of care (managerial CC) were found (around 70%). Among the associated factors with CC, the following stand out: in Brazil, age (elderly) and area (Caruaru, remote town) was associated with any type of CC. In both countries, poor self-rated health was associated with lower levels of relational CC and in Colombia, also, with clinical management CC. In addition, in Colombia, having at least one chronic disease was associated with higher levels of any type of CC and sex (female) with a continuous relationship with PC physicians and informational CC. Conclusions The level of perceived relational and managerial continuity is high, and of informational continuity, low. Factors associated with the perception of continuity of care differ by countries and type of continuity of care. Key messages It is the first attempt to evaluate the three types of continuity of care in areas of Colombia and Brazil The understanding of the factors associated with the continuity of care will reveal which aspects of the public health system could be improve