Variaciones estacionales y espaciales de la comunidad de larvas de peces de Gran Canaria, Islas Canarias

Temporal and spatial variations of the larval fish community off the island of Gran Canaria (Canary Islands) were studied in weekly surveys from October 2005 to June 2006. A total of 156 taxa, belonging to 51 families and 15 orders, were identified. Myctophidae was by far the most abundant family (30%), followed by Sparidae (11%), Clupeidae (9%) and Gonostomatidae (7%). As expected for an oceanic island, neritic and oceanic taxa contributed in similar proportions. Leeward and windward retention areas were found for total egg and neritic larval abundance. However, seasonality showed a stronger influence on the annual larval assemblage than sampling site, as the latter was not significant on a long time scale. Results suggest that there are two seasonal larval assemblages corresponding to the two main characteristic periods of the water column in these waters: mixing (winter) and stratification (summer). In addition, a significant relationship was recorded between lunar illumination and small mesozooplankton biomass, suggesting that this relationship may be extended to certain neritic families. The most abundant neritic larvae (Sparidae) showed this lunar pattern, which partially supports a recent hypothesis about the effect of lunar illumination on larval fish survival and development in subtropical waters.Se estudiaron las variaciones temporales y espaciales en la comunidad de larvas de peces de la isla de Gran Canaria (Islas Canarias) a partir de muestreos semanales desde octubre 2005 a junio 2006. Se identificaron un total de 156 taxones, pertene- cientes a 51 familias y 15 órdenes. La familia Myctophidae fue la más abundante (30%), seguida por Sparidae (11%), Clupei- dae (9%) y gonostomatidae (7%). Como es de esperar en una isla oceánica, los taxones neríticos y oceánicos contribuyeron en proporciones similares. Se encontraron dos zonas de retención para huevos y larvas de especies neríticas, a sotavento y barlovento de la isla. Sin embargo, la estacionalidad mostró una mayor influencia en la estructura de la comunidad larvaria que la zona de muestreo, siendo ésta no significativa a largo plazo. Se observaron dos asociaciones estacionales de larvas correspondiendo con los dos períodos más característicos en la columna de agua: periodo de mezcla (invierno) y de estrati- ficación (verano). además, se encontró una relación significativa entre la iluminación lunar y la biomasa del zooplancton de pequeño tamaño, que podría ser extensible a las larvas neríticas. Las larvas neríticas más abundantes (Sparidae) mostraron una relación con el ciclo lunar, apoyando parcialmente una hipótesis reciente sobre el efecto de la iluminación lunar en la supervivencia larvaria y su desarrollo en aguas subtropicales

Distribución horizontal de las larvas de invertebrados alrededor de la isla oceánica de Gran Canaria: Efecto de la variabilidad de mesoescala

11 pages, 7 figures, 1 table.-- Published online 21 April 2009.[EN] In October 1991, the horizontal distribution of invertebrate larvae was studied in the waters surrounding the island of Gran Canaria (Canary Islands). The cruise was typified by the presence of three recurrent mesoscale hydrographic structures: a cyclonic eddy southwest of the island, a warm lee region downstream of the island and the offshore boundary of an upwelling filament from the African coast reaching the southeast of the island. Decapod larvae were the most abundant group. In general, a rather high spatial variability was found. The horizontal distribution of the invertebrate larvae groups showed that the highest values of abundance occurred in an elongated zone around the island oriented in the overall direction of flow, leeward and windward of the island, while the lowest values occurred off the eastern and western flanks of the islands. On the other hand, Stomatopoda and Mollusca larvae showed a distribution associated with the boundary of the upwelling filament and decapod larvae of pelagic species were distributed around the eddy structure. Our results suggest specific retention mechanisms for the larvae of neritic invertebrate populations that are related to the particular physical oceanography around Gran Canaria.[ES] Se estudió la distribución horizontal de las larvas de invertebrados alrededor de la isla de Gran Canaria (Islas Canarias) en octubre de 1991. La campaña se caracterizó por la presencia de tres fenómenos oceanográficos de mesoescala recurrentes: un remolino ciclónico al suroeste de la isla, la estela cálida a sotavento de la misma y el borde de un filamento proveniente del afloramiento africano situado al sureste de Gran Canaria. Las larvas de crustáceos decápodos fueron las más abundantes. En general, las larvas de los diferentes taxa estudiados mostraron una gran variabilidad en cuanto a su distribución espacial. La distribución horizontal de las larvas de los diferentes grupos de invertebrados mostró que las densidades más altas se registraban alrededor de la isla en la banda cercana y orientada hacia el suroeste, en la dirección del flujo, mientras que los valores más bajos se encontraron en el norte y en los flancos este y oeste de la isla. Por otro lado, las larvas de estomatópodos y moluscos presentaron una distribución asociada al frente del filamento, mientras que las larvas de decápodos pelágicos se distribuyeron en torno al remolino ciclónico. Los resultados obtenidos sugieren la existencia de mecanismos de retención específicos para el mantenimiento de las poblaciones insulares, relacionados con los procesos físicos de mesoescala predominantes.This work was funded by the MAST 0031 project of the European Union and the ConAfrica project (CICYT, CTM2004-02319) of the Ministerio de Educación y Ciencia. JML was supported by a postgraduate grant (BES-2005-10960) from the European Social Fund.Peer reviewe

Granulometría, morfometría y mineralogía de polvo atmosférico que entra a la cuenca canaria: evidencia de retención de partículas de hierro en la capa de mezcla

Aeolian dust plays an important role in climate and ocean processes. Particularly, Saharan dust deposition is of importance in the Canary Current due to its content of iron minerals, which are fertilizers of the ocean. In this work, dust particles are characterized mainly by granulometry, morphometry and mineralogy, using image processing and scanning northern Mauritania and the Western Sahara. The concentration of terrigenous material was measured in three environments: the atmosphere (300 m above sea level), the mixed layer at 10 m depth, and 150 m depth. Samples were collected before and during the dust events, thus allowing the effect of Saharan dust inputs in the water column to be assessed. The dominant grain size was coarse silt. Dominant minerals were iron oxy-hydroxides, silicates and Ca-Mg carbonates. A relative increase of iron mineral particles (hematite and goethite) was detected in the mixed layer, reflecting a higher permanence of iron in the water column despite the greater relative density of these minerals in comparison with the other minerals. This higher iron particle permanence does not appear to be explained by physical processes. The retention of this metal by colloids or microorganisms is suggested to explain its long residence time in the mixed layer.El polvo atmosférico juega un papel importante en el clima y en los procesos oceánicos, particularmente la deposición del polvo sahariano es de suma importancia en la corriente canaria debido a que contiene minerales de hierro que actúan como fertilizante del océano. En este trabajo las partículas de polvo fueron caracterizadas mediante granulometría, morfometría y mineralogía, usando procesamiento de imágenes, microscopia electrónica (SEM-EDS). El polvo analizado en este estudio fue generado al norte de Mauritania y Sahara Occidental. Su concentración fue medida en tres ambientes diferentes: la atmósfera (300 m.s.n.m.), la capa de mezcla (10 m de profundidad) y a 150 m de profundidad). Las muestras fueron colectadas antes y durante los eventos de polvo, permitiendo la determinación del efecto del aporte de polvo sahariano a la columna de agua. El tamaño de grano predominante fueron los limos gruesos. Los minerales dominantes fueron oxi-hidróxidos, silicatos y carbonatos. Un incremento de partículas ricas en hierro (hematita y goetita) fue detectado en la capa de mezcla, reflejando una alta permanencia del hierro en la columna de agua a pesar de la alta densidad que presentan esos minerales con respecto a otros. Esta alta permanencia de hierro no parece ser explicada por procesos físicos. La retención de este metal por coloides o microrganismos es la explicación sugerida ante el alto tiempo de residencia en la capa de mezcla

A 50-year (1971–2021) mesozooplankton biomass data collection in the Canary Current System: Base line, gaps, trends, and future prospect

Mesozooplankton have been widely used as a bioindicator of marine ecosystems due to their key position in ocean food webs, rapid response to environmental changes, and ubiquity. Here, we show mesozooplankton biomass values in the Canary Current System from 1971 to 2021 in three different areas in relation to mesoscale activity: (1) scarcely affected by mesoscales structures (North of the Canary Islands), (2) affected by mesoscale activity and the presence of the islands (South and around the islands), and (3) close to the Northwest African coastal upwelling system (Upwelling influenced). A Generalized Additive Mixed Model (GAMM) was used to analyze the general mesozooplankton biomass trend throughout the studied period discriminating differences in biomass between the areas, annual cycle, and day-nighttime periods. The GAMM showed a significant negative biomass tendency North of the Canary Islands over the 50-year time-series compared to the South and around the islands, and significant differences between day and nighttime periods (p < 0.001) and the annual cycle (p < 0.0001). Linear regression analyses showed different tendencies depending on the area, season, and period. When comparing biomass data of the most oligotrophic zone (north of the islands) with other tropical-subtropical time-series stations in Hawaii (HOTS) and Bermuda (BATS), we obtained increasing biomass tendencies for both fixed time stations but decreasing tendency for our time-series

Proyecto de homologación de las reformas efectuadas en el motor, la suspensión y la carrocería de un vehículo para utilización mixta del vehículo en uso ocasional y en pruebas de coches clásicos

El presente trabajo de fin de grado estudia las reformas realizadas en un BMW 320-i E30 en base a lo regulado por la legislación vigente en materia de reformas de vehículos. La reglamentación viene determinada por el Real Decreto 866/2010, de 2 de julio, un documento que se diseñó con el fin de mantener unos estándares de calidad y seguridad en los vehículos reformados en coherencia con la normativa a nivel europeo. En la apertura del proyecto se realiza una presentación del vehículo, exponiendo de forma los distintos sistemas reformados, y detallando en qué consisten las reformas y a qué sistemas del vehículo afectan, así como en qué medida se recogen en la regulación vigente. Estas reformas afectan a prácticamente la totalidad del vehículo; desde el sistema de dirección, el sistema de frenos o el conjunto de motor y transmisión, hasta el sistema de dirección o la carrocería del vehículo.En la memoria del documento se encuentra una recopilación de datos, todos ellos necesarios para la justificación y realización de los cálculos necesarios para demostrar la aptitud de las reformas. Se detallan las partes instaladas, modificadas o eliminadas, incluyendo las referencias identificativas y su procedencia, o las características de los materiales empleados para los elementos que así lo requieren en su posterior cálculo.En el apartado de cálculos justificativos se realiza un análisis detallado de los distintos sistemas reformados, útiles para garantizar la aptitud de las reformas. Cabe destacar que a lo largo del mismo se han realizado una serie de simplificaciones. Para el cálculo del sistema de transmisión se han calculado los desarrollos que alcanzaría el vehículo si fuera capaz de superar todas las fuerzas de resistencia. Mientras en el caso del cálculo de los frenos se llevó a cabo una simplificación lineal, sintetizando en la medida de lo posible al no considerar el efecto de las inercias y torsiones. Se utiliza el software de diseño 3D SolidWorks para el diseño y simulación de esfuerzos y deformaciones de la estructura de seguridad. Se realizan, además, cálculos justificativos sobre los elementos del sistema de suspensión, muelles y amortiguadores donde se demuestra la idoneidad del elemento elástico para soportar las cargas del vehículo y del conjunto para trabajar en régimen subamortiguado. Por otro lado, también se recoge un estudio de la viabilidad de las uniones escogidas, tanto para la estructura de seguridad, como para el alerón, instalados en el vehículo. A su vez, se exponen algunas características, en referencia a los sistemas de dirección y la instalación de las barras estabilizadoras, que por sí mismas justifican la viabilidad de las reformas, de acuerdo con la normativa vigente, sin necesidad de cálculos que las avalen.En definitiva, este proyecto demuestra la viabilidad de las reformas realizadas de acuerdo con la normativa vigente, permitiendo la circulación lícita por la vía pública, al tiempo que se logra mejorar los sistemas de acuerdo con el uso deportivo que se prevé del vehículo. <br /

Krill as a central node for iron cycling in the Southern Ocean

In order to establish the potential role of Antarctic krill (Euphausia superba) in the recycling of bioactive elements, we have quantified the release of iron, phosphate, and ammonia by these organisms along the Antarctic Peninsula sector of the Southern Ocean. The experimental results suggested that the presence of krill has a significant impact on ambient iron concentrations, as large amounts of this trace element were released by the krill (22-689 nmol Fe g Dry Weight-1 h-1, equivalent to 0.2 to 4.3 nmol Fe L-1 d-1). Half of this iron release occurred within the first hour of the experiment, and differences in iron and phosphate release rates (3.1 to 14.0 μmol PO4 3- g DW-1 h-1) seemed to reflect differences in food availability. These results identify krill as a major node in iron cycling in the Southern Ocean, potentially influencing iron residence time in the upper water column of this region. Copyright 2007 by the American Geophysical Union.Peer Reviewe

Vision-based techniques for automatic marine plankton classification

Plankton are an important component of life on Earth. Since the 19th century, scientists have attempted to quantify species distributions using many techniques, such as direct counting, sizing, and classification with microscopes. Since then, extraordinary work has been performed regarding the development of plankton imaging systems, producing a massive backlog of images that await classification. Automatic image processing and classification approaches are opening new avenues for avoiding time-consuming manual procedures. While some algorithms have been adapted from many other applications for use with plankton, other exciting techniques have been developed exclusively for this issue. Achieving higher accuracy than that of human taxonomists is not yet possible, but an expeditious analysis is essential for discovering the world beyond plankton. Recent studies have shown the imminent development of real-time, in situ plankton image classification systems, which have only been slowed down by the complex implementations of algorithms on low-power processing hardware. This article compiles the techniques that have been proposed for classifying marine plankton, focusing on automatic methods that utilize image processing, from the beginnings of this field to the present day.Funding for open access charge: Universidad de Málaga / CBUA. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The authors wish to thank Alonso Hernández-Guerra for his frm support in the development of oceanographic technology. Special thanks to Laia Armengol for her help in the domain of plankton. This study has been funded by Feder of the UE through the RES-COAST Mac-Interreg pro ject (MAC2/3.5b/314). We also acknowledge the European Union projects SUMMER (Grant Agreement 817806) and TRIATLAS (Grant Agreement 817578) from the Horizon 2020 Research and Innovation Programme and the Ministry of Science from the Spanish Government through the Project DESAFÍO (PID2020-118118RB-I00)

Annual cycle of zooplankton biomass, abundance and species composition in the neritic area of the Balearic Sea, western Mediterranean

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Bottom-up control of sardine and anchovy population cycles in the canary current: insights from an end-to-end model simulation

Sardine and anchovy can exhibit dramatic decadal-scale shifts in abundance in response to climate variability. Sharpe declines of these populations entail particularly serious commercial and ecological consequences in eastern boundary current ecosystems, where they sustain major world fisheries and provide the forage for a broad variety of predators. Understanding the mechanisms and environmental forcing that drive the observed fish variability remains a challenging problem. The modelling study presented here provides an approach that bridges a comprehensive database with an end-to-end modelling framework enabling the investigation of the sources of variability of sardine and anchovy in the Canary Current System. Different biological traits and behaviour prescribed for sardine and anchovy gave rise to different distribution and displacements of the populations, but to a rather synchronous variability in terms of abundance and biomass, in qualitative agreement with historical landing records. Analysis of years with anomalously high increase and decline of the adult population points to food availability (instead of temperature or other environmental drivers) as the main environmental factor determining recruitment for both sardine (via spawning and survival of feeding age-0 individuals) and anchovy (via survival of feeding age-0). Consistent with this, the two species thrive under enhanced upwelling-favourable winds, but only up to some threshold of the wind velocity beyond which larval drift mortality exceeds the positive effect of the extra food supply. Based on the analysis of the simulation, we found that anchovy larvae are particularly vulnerable to enhanced wind-driven advection, and as such do better with more moderate upwelling than sardines.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Population distribution and biomass variability of sardine and anchovy in the Canary current system as simulated by an end-to-end coupled model

Small pelagic fishes as sardine and anchovy account for as much as 20-25% of the world fisheries catch. They are particularly abundant in the four major eastern boundary upwelling ecosystems, where high levels of biological productivity are sustained by the supply of nutrient-rich water from beneath the photic zone. An intrinsic and puzzling feature of small pelagic fish is the large fluctuations of their population, typically occurring at decadal scales. The causes for such fluctuations have been extensively analyzed and discussed in the literature, yet our understanding of the mechanism involved is very limited. End-to-end models are emerging tools useful to test hypothesis for such fish population variability or to gain new insights into the problem. This comprehensive and complex model approach is now becoming possible largely thanks to the present-day computer power. This contribution focuses on the population dynamics of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) in the Canary Current Upwelling Ecosystem. We describe and present the results of an end-to-end coupled model simulation including these two small pelagic species. The end-to-end application includes three model components: the ROMS circulation sub-model, the lower trophic ecosystem sub-model NEMURO, and a recently developed individual-based model for the fish (Rose et al. 2015; Fiechter et al. 2015). The computational grid for the three models covers NW Africa and the Western Iberian Peninsula at a spatial resolution of 12 km. This resolution is sufficient for certain eddy variability to occur in ROMS. Different biological traits were prescribed for anchovy and sardine: temperature optimum, diet preferences, and the onset and duration of the spawning season, among others. A hind-cast simulation of the period 1958-2007 was carried out. Model results reveal a fairly different behavior of sardine and anchovy. Anchovies gather off the northern part of Morocco and the Gulf of Cadiz, whereas sardines appear more scattered across the domain, further offshore, and further south, where upwelling favorable conditions take place year round. Both species exhibit decadal-scale fluctuations in both the location of the center of mass of the population and their biomass abundance; the latter being reasonably correlated with historical landing records.Universidad de Málaga. Campus de Excelencia Internacional del Mar CEIMAR. Campus de Excelencia Andalucía Tec