Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

Oxygen isotope ratios from fish otoliths are used to discriminate marine stocks and reconstruct past climate, assuming that variations in otolith δ18O values closely reflect differences in temperature history of fish when accounting for salinity induced variability in water δ18O. To investigate this, we exploited the environmental and migratory data gathered from a decade using archival tags to study the behaviour of adult plaice (Pleuronectes platessa L.) in the North Sea. Based on the tag-derived monthly distributions of the fish and corresponding temperature and salinity estimates modelled across three consecutive years, we first predicted annual otolith δ18O values for three geographically discrete offshore sub-stocks, using three alternative plausible scenarios for otolith growth. Comparison of predicted vs. measured annual δ18O values demonstrated >96% correct prediction of sub-stock membership, irrespective of the otolith growth scenario. Pronounced inter-stock differences in δ18O values, notably in summer, provide a robust marker for reconstructing broad-scale plaice distribution in the North Sea. However, although largely congruent, measured and predicted annual δ18O values of did not fully match. Small, but consistent, offsets were also observed between individual high-resolution otolith δ18O values measured during tag recording time and corresponding δ18O predictions using concomitant tag-recorded temperatures and location-specific salinity estimates. The nature of the shifts differed among sub-stocks, suggesting specific vital effects linked to variation in physiological response to temperature. Therefore, although otolith δ18O in free-ranging fish largely reflects environmental temperature and salinity, we counsel prudence when interpreting otolith δ18O data for stock discrimination or temperature reconstruction until the mechanisms underpinning otolith δ18O signature acquisition, and associated variation, are clarified

Regional adaptation defines sensitivity to future ocean acidification

Physiological responses to temperature are known to be a major determinant of species distributions and can dictate the sensitivity of populations to global warming. In contrast, little is known about how other major global change drivers, such as ocean acidification (OA), will shape species distributions in the future. Here, by integrating population genetics with experimental data for growth and mineralization, physiology and metabolomics, we demonstrate that the sensitivity of populations of the gastropod Littorina littorea to future OA is shaped by regional adaptation. Individuals from populations towards the edges of the natural latitudinal range in the Northeast Atlantic exhibit greater shell dissolution and the inability to upregulate their metabolism when exposed to low pH, thus appearing most sensitive to low seawater pH. Our results suggest that future levels of OA could mediate temperature-driven shifts in species distributions, thereby influencing future biogeography and the functioning of marine ecosystems

Effects of ocean acidification on the shells of four Mediterranean gastropod species near a CO 2 seep

Marine CO2seeps allow the study of the long-term effects of elevated pCO2(ocean acidification) on marine invertebrate biomineralization. We investigated the effects of ocean acidification on shell composition and structure in four ecologically important species of Mediterranean gastropods (two limpets, a top-shell snail, and a whelk). Individuals were sampled from three sites near a volcanic CO2seep off Vulcano Island, Italy. The three sites represented ambient (8.15 pH), moderate (8.03 pH) and low (7.73 pH) seawater mean pH. Shell mineralogy, microstructure, and mechanical strength were examined in all four species. We found that the calcite/aragonite ratio could vary and increased significantly with reduced pH in shells of one of the two limpet species. Moreover, each of the four gastropods displayed reductions in either inner shell toughness or elasticity at the Low pH site. These results suggest that near-future ocean acidification could alter shell biomineralization and structure in these common gastropods

Recuperación precoz tras cirugía cardiaca en una unidad de reanimación posquirúrgica

La técnica conocida como "fast-track" o técnica de "recuperación precoz" es un proceso de planificación del periodo perioperatorio de los pacientes intervenidos de cirugía cardiaca (CC) que tiene como objetivo el no prolongar la intubación traqueal y la ventilación mecánica. El objetivo de nuestro estudio fue observar si los pacientes intervenidos de CC ingresados en nuestra URPA, eran extubados antes que los pacientes ingresados directamente en la unidad de cuidados intensivos de CC (UCIC) y si esto repercutía en la estancia en la UCIC y en el hospital y en la incidencia de complicaciones postoperatorias. Este grupo "fast-track", 109 pacientes (Grupo I) se comparó con un grupo control de 40 pacientes (Grupo II) intervenidos de CC durante el mismo periodo de tiempo y que fueron ingresados directamente en la UCIC. En ambos grupos se valoraron el tiempo de intubación, la estancia en la UCIC y en el hospital, las complicaciones postoperatorias y la mortalidad hospitalaria. Al finalizar la cirugía, los pacientes del Grupo I, fueron trasladados a la URPA, hasta que eran extubados. Los pacientes del Grupo II, fueron trasladados directamente a la UCIC. Las complicaciones de ambos grupos en UCIC fueron similares. En conclusión, nuestros resultados indican que la técnica de "fast-track" realizada en una URPA permite acortar el tiempo de ventilación mecánica y de intubación sin aumento de la mortalidad y morbilidad de los pacientes

Feeding behavior of the infaunal bivalve Tagelus dombeii (Lamarck, 1818). Suspension vs. deposit feeding

The feeding behavior of two populations of the bivalve Tagelus dombeii (Lamarck, 1818) was studied through laboratory experiments, with the purpose of establishing a possible dual feeding strategy (suspensivore/detritivore). Individuals from both the intertidal population of Coihuín (near Puerto Montt, Chile) as well as those from the subtidal of Corral Bay (near Valdivia) showed continuous suspension feeding with total absence of deposit feeding when immersed, and always showed their open siphons flush with the sediment surface. These observations were confirmed by the high clearance rates shown by both populations of T. dombeii, similar to the ones described for obligate suspension feeding bivalves. Different results were obtained during emersion, since T. dombeii individuals from both populations displayed their siphons on the sediment (3-5 cm), thus behaving as deposit feeders. Deposit feeding was observed in up to 80% of individuals. The present study allows to conclude that T. dombeii is primarily a suspension-feeder, which might be related to the dominance of sand (>92%) in the habitat of both populations studied. Growth coincides with periods of suspended particulate food supply increase in the natural environment. This suggests that T. dombeii would be competing for the particulate food supply with the community of obligate suspension feeding bivalves in these habitats.El comportamiento alimentario de dos poblaciones del bivalvo Tagelus dombeii (Lamarck, 1818) fue estudiado mediante experimentos de laboratorio, con el objetivo de confirmar una posible estrategia dual de alimentación (suspensívora/detritívora). Individuos provenientes de la población intermareal de Coihuín (cerca de Puerto Montt, Chile) así como aquellos del submareal de Corral mostraron una conducta de alimentación por suspensión cuando estuvieron sumergidos, con una ausencia total de alimentación de depósito y con los sifones siempre abiertos a nivel de la superficie del sedimento. Estas observaciones fueron confirmadas por altas tasas de aclaramiento mostradas por ambas poblaciones de T. dombeii, similar a las descritas para bivalvos suspensívoros obligados. Resultados diferentes fueron obtenidos durante la emersión, cuando los individuos de T. dombeii de ambas poblaciones desplegaron sus sifones sobre el sedimento (3-5 cm), comportándose como alimentadores de depósito. La alimentación de depósito fue observada hasta en el 80% de los individuos. Este estudio permite concluir que T. dombeii es principalmente un organismo con alimentación por suspensión, un hecho que podría estar relacionado con el tipo de sedimento disponible en el hábitat de las dos poblaciones estudiadas, que está compuesto principalmente por la fracción de arena (>92%). El período de crecimiento de esta especie coincide con los períodos de aumento de la oferta de alimento en su medio ambiente. Este hecho sugiere que T. dombeii estaría compitiendo por la oferta de alimento con la comunidad de bivalvos suspensívoros obligados en estos hábitats

Multi-rate and multi-hop optical carriers in WDM ring

By means of optical transparency wavelength division multiplexing (WDM) networks with multi-rate transmissions are becoming a reality. The potential advantages of individually selecting the transmission rate for each lightpath are however not yet fully understood. A recent work studied for the first time multi-rate and multi-hop (M&M) networks in which tributary signals are transmitted over a concatenation of lightpaths, each one operating at its own transmission rate. The study revealed that the problem of designing M&M networks is NP-complete and optimal solutions are practically available only for small networks. The paper presents a heuristic algorithm for designing M&M ring networks that yields efficient sub-optimal solutions in polynomial time. The algorithm determines the rate for each lightpath taking into account a number of factors including the node's interface, amount of multiplexed traffic and cost of the network components. The potential advantages provided by the M&M network when compared to first generation optical networks (i.e., SONET/SDH), single- and multi-hop (constant bit rate) optical networks, are discussed in the paper and documented with numerical results. Presented results show that the network cost reduction achieved by the M&M design is a function of the cost ratio between the optical bandwidth (wavelengths) and the optical terminals