Trophic indices for micronektonic fishes reveal their dependence on the microbial system in the North Atlantic.

This research was funded by projects BATHYPELAGIC (CTM2016-78853-R) from the Plan Estatal de I+D+I (Spain), SUMMER (Grant Agreement 817806) and TRIATLAS (Grant Agreement 817578), from the European Union (Horizon 2020 Research and Innovation Programme), and Grant Number IN607A2018/2 from the Axencia Galega de Innovación (GAIN, Xunta de Galicia, Spain).The importance of microbes for the functioning of oceanic food webs is well established, but their relevance for top consumers is still poorly appreciated. Large differences in individual size, and consequently in growth rates and the relevant spatial and temporal scales involved, make the integration of microorganisms and large metazoans in a common food web framework difficult. Using stable isotopes, this study estimated the trophic position of 13 species of micronektonic fishes to examine the microbial and metazoan contribution to mid trophic level consumers. Vertically migrant species displayed higher trophic positions than non-migrant species in all depth layers. The estimated trophic positions agreed well with those from the literature, but all species displayed mean increases between 0.5 and 0.8 trophic positions when taking into account microbial trophic steps. Trophic position, but not the relative importance of the microbial food web, increased with individual size, suggesting that current estimates of the trophic position of top consumers and of the length of oceanic food webs are too low because they are based only on metazoan trophic steps. This finding calls for a review of trophic position estimates and of the efficiency of trophic transfers along oceanic food webs.This research was funded by projects BATHYPELAGIC (CTM2016-78853-R) from the Plan Estatal de I+D+I (Spain), SUMMER (Grant Agreement 817806) and TRIATLAS (Grant Agreement 817578), from the European Union (Horizon 2020 Research and Innovation Programme), and Grant Number IN607A2018/2 from the Axencia Galega de Innovación (GAIN, Xunta de Galicia, Spain).En prensa2,92

A revised distance to IRAS 16293−-2422 from VLBA astrometry of associated water masers

IRAS 16293-2422 is a very well studied young stellar system seen in projection towards the L1689N cloud in the Ophiuchus complex. However, its distance is still uncertain with a range of values from 120 pc to 180 pc. Our goal is to measure the trigonometric parallax of this young star by means of H$_2$O maser emission. We use archival data from 15 epochs of VLBA observations of the 22.2 GHz water maser line. By modeling the displacement on the sky of the H$_2$O maser spots, we derived a trigonometric parallax of $7.1\pm1.3$ mas, corresponding to a distance of $141_{-21}^{+30}$ pc. This new distance is in good agreement with recent values obtained for other magnetically active young stars in the L1689 cloud. We relate the kinematics of these masers with the outflows and the recent ejections powered by source A in the system.Comment: 14 pages, 6 tables, 8 figures. Accepted to be published in Astronomy \& Astrophysic

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

Publicado

Zooplankton biomass and indices of feeding and metabolism in relation to an upwelling filament off northwest Africa

Zooplankton biomass and indices of grazing (gut fluorescence), respiration (electron transfer system activity, ETS) and growth (aspartate transcarbamylase, ATC) were studied in relation to an upwelling filament off northwest Africa during August 1993. The filament extended 150 km offshore into the oligotrophic waters. It was generated by a trapped, quasi-permanent cyclonic eddy located between the Canary Islands and the African shelf. High biomass, specific gut fluorescence and electron transfer system activity in zooplankton were observed along the filament structure. In contrast, low values of biomass, gut fluorescence, ETS and ATC specific activities were found in the center of the trapped cyclonic eddy. Assuming a 50% of pigment destruction, the calculated grazing impact of zooplankton on primary production varied between 16 and 97%, a high range compared to other oceanic systems. Ingestion, estimated from indices of metabolism and growth, accounted for 47–296% of the primary production (assuming an herbivorous feeding). Mesozooplankton transported offshore into the oligotrophic area fulfilled their metabolic demands with nonpigmented food as observed from the increase of omnivory from the coastal waters to the open ocean. The progressive decay of grazing and metabolic indices along the filament suggests that advection, rather than local enrichment processes, is mostly responsible for the high biomass values in this physical structure

Calibración a nivel de Hardware de un detector Cherenkov de agua (Chitaga) en el arreglo GUANE para estudios de clima espacial

Water Cherenkov Detectors (WCDs) play an essential role in space weather and cosmic rays studies around the world. In this article, we present a general methodology to calibrate a WCD based finding its optimum operation point and counting the delay time of the transmission cables. The dynode charge histogram of the WCD and CORSIKA simulations validate this methodology. Finally, to illustrate the capability of WCD tomeasure fluctuations in the secondary CR flux, we studied the 07.09.2017 Forbush and compared our measurements with data obtained from the Neutron Flux Monitor at UNAM and the Kyoto Dst index service.Los detectores Cherenkov de agua (WCD, por sus siglas en inglés) desempeñan un papel esencial en el estudio del clima espacial y los rayos cósmicos en todo el mundo. En este artículo, presentamos una metodología general para calibrar un WCD basado en encontrar su punto de operación óptimo y contarel tiempo de retardo de los cables de transmisión. El histograma de carga de dinodos de las simulaciones WCD y CORSIKA valida esta metodología. Finalmente, para ilustrar la capacidad de WCD para medir las fluctuaciones en el flujo de CR secundario, estudiamos el Forbush ocuurido el dia 07.09.2017 y comparamosnuestras mediciones con los datos obtenidos del Monitor de flujo de neutrones en la UNAM y el servicio de índice Dst de Kyoto

Calibración a nivel de Hardware de un detector Cherenkov de agua (Chitaga) en el arreglo GUANE para estudios de clima espacial

Water Cherenkov Detectors (WCDs) play an essential role in space weather and cosmic rays studies around the world. In this article, we present a general methodology to calibrate a WCD based finding its optimum operation point and counting the delay time of the transmission cables. The dynode charge histogram of the WCD and CORSIKA simulations validate this methodology. Finally, to illustrate the capability of WCD tomeasure fluctuations in the secondary CR flux, we studied the 07.09.2017 Forbush and compared our measurements with data obtained from the Neutron Flux Monitor at UNAM and the Kyoto Dst index service.Los detectores Cherenkov de agua (WCD, por sus siglas en inglés) desempeñan un papel esencial en el estudio del clima espacial y los rayos cósmicos en todo el mundo. En este artículo, presentamos una metodología general para calibrar un WCD basado en encontrar su punto de operación óptimo y contarel tiempo de retardo de los cables de transmisión. El histograma de carga de dinodos de las simulaciones WCD y CORSIKA valida esta metodología. Finalmente, para ilustrar la capacidad de WCD para medir las fluctuaciones en el flujo de CR secundario, estudiamos el Forbush ocuurido el dia 07.09.2017 y comparamosnuestras mediciones con los datos obtenidos del Monitor de flujo de neutrones en la UNAM y el servicio de índice Dst de Kyoto

Development of Surface-Coated Polylactic Acid/Polyhydroxyalkanoate (PLA/PHA) Nanocomposites

This work reports on the design and development of nanocomposites based on a polymeric matrix containing biodegradable Polylactic Acid (PLA) and Polyhydroxyalkanoate (PHA) coated with either Graphite NanoPlatelets (GNP) or silver nanoparticles (AgNP). Nanocomposites were obtained by mechanical mixing under mild conditions and low load contents (<0.10 wt %). This favours physical adhesion of the additives onto the polymer surface, while the polymeric bulk matrix remains unaffected. Nanocomposite characterisation was performed via optical and focused ion beam microscopy, proving these nanocomposites are selectively modified only on the surface, leaving bulk polymer unaffected. Processability of these materials was proven by the fabrication of samples via injection moulding and mechanical characterisation. Nanocomposites showed enhanced Young modulus and yield strength, as well as better thermal properties when compared with the unmodified polymer. In the case of AgNP coated nanocomposites, the surface was found to be optically active, as observed in the increase of the resolution of Raman spectra, acquired at least 10 times, proving these nanocomposites are promising candidates as surface enhanced Raman spectroscopy (SERS) substrates