Handling magnetic and structural properties of EuMnO3 thin films by the combined effect of Lu doping and substrate strain

This work aims to understand the alterations induced by film/substrate lattice mismatch in structure, lattice dynamics and magnetic response of orthorhombic Eu1-xLuxMnO3 thin films within the range 0 ≤ x ≤ 0.4, when compared to results reported for ceramics with analogous composition. Thin films, which have been deposited onto Pt/Ti/SiO2/Si(100) oriented substrates via chemical method, exhibit noteworthy modifications in the magnetic ordering properties and, contrary to ceramics, do not show any sharp phase transition to the paramagnetic state. This reveals an induced ferromagnetic response in the films which is stable up to 100 K. X-ray diffraction and Raman spectroscopy measurements have been performed to identify the mechanically compressive state induced by the substrate and Lu doping. This facilitates insight into the magnetoelastic coupling effect in these films which is driven by alterations in electronic orbital overlapping and the associated antiferromagnetic superexchange interactions.publishe

Response of phytoplankton to enhanced atmospheric and riverine nutrient inputs in a coastal upwelling embayment

Original research paperOver the past decades, as a consequence of human activity, there was an increase in nutrient inputs to the ocean and they are expected to enhance even more in the future. Coastal areas, accounting for a significant proportion of marine primary productivity, are the most vulnerable zones to anthropogenic impacts. The response of phytoplankton communities to an increase in organic and inorganic nutrients levels from natural allochthonous sources was assessed in microcosm experiments conducted in a coastal system affected by intermittent upwelling events (Ría de Vigo, NW Iberia). Three nutrient addition experiments were performed in spring, summer and autumn, when surface water was supplemented with 5 and 10% of atmospheric and riverine matter. Pico-, nano- and microphytoplankton abundances, chlorophyll a concentration (Chl a) and primary production rates (PP) were measured and compared with those in the control seawater sample (without additions) after 48 h of incubation. Simultaneous experiments with controlled additions of inorganic and organic nutrients were also performed in order to describe the limiting nutrient for phytoplankton growth at each experiment. The composition of the matter inputs and the structure of the phytoplankton communities determined the type of response observed. Phytoplankton responses varied among seasons, being positively correlated with dissolved inorganic nitrogen (DIN) concentrations. As expected, the phytoplankton responses to external nutrient inputs were stronger under low nutrient levels (summer) than when phytoplankton was already growing in nutrient replete conditions (spring). Null and negative responses to the natural inputs were observed in autumn, which suggests that the oceanic phytoplankton advected to this coastal system during downwelling events could be occasionally inhibited by these nutrient inputs. In a future global change scenario, characterized by enhanced nutrient inputs from riverine and atmospheric origin, the response of phytoplankton communities will strongly depend on the concentration and chemical composition of these inputs and on the structure of phytoplankton communities able to respond to themSpanish Ministry of Science and Innovation (project REIMAGE CTM2011-30155); Spanish Ministry of Economy and Competitiviness (project iSmall, reference CTM2014-56119-R); Portuguese Foundation for Science and Technology (reference SFRH/BPD/188485/2015); ESF (reference JAE DOC 040) and MINECO (project FERMIO reference CTM2014-57334-JIN)Versión del edito

The microplankton succession in the Ría de Vigo revisited: species assemblages and the role of weather-induced, hydrodynamic variability

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Effect of meteorological and hydrographic disturbances on the microplankton community structure in the Ría de Vigo (NW Spain)

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Selection of Gymnodinium catenatum under downwelling conditions in the Ria de Vigo

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Role of microzooplankton during a Phaeocystis sp. bloom in the Oosterschelde (SW Netherlands)

The impact of microzooplankton on the plankton community was assessed during a bloom of Phaeocystis sp. in the Oosterschelde basin (SW Netherlands). Chlorophyll a concentration and Phaeocystis sp. abundance reached maxima values in the middle of the sampling period (~ 27 mg chl a m− 3 and 3.4 × 1010 cells m− 3, respectively). The bloom collapse coincided with the last sampling day, when accentuated decreases in chlorophyll a concentrations (~ 11 mg chl a m− 3) and Phaeocystis sp. cells numbers (~ 1.3 × 1010 cells m− 3) were recorded. Microzooplankton organisms were significant consumers of both phytoplankton and heterotrophic plankton. Although Phaeocystis sp. was the most consumed organism (336 ± 71 mg C m− 3 d− 1), microzooplankton impact on its standing stock was lower than on the stocks of other less abundant organisms. This impact was also lower during the peak of the bloom, when colonial forms of Phaeocystis sp. presumably predominated, than during the bloom collapse, when free-living cells were supposedly more abundant. The impact of microzooplankton on heterotrophic organisms was higher than on phytoplankton, and increased when the bloom collapsed. Picoheterotrophs experienced the highest impact on their standing stock (~ 75% d− 1) and production (~ 90% d− 1). These results demonstrate that during a Phaeocystis sp. bloom, the microbial food web was responsible for channelling a significant fraction of plankton biomass, either from direct consumption of Phaeocystis sp. cells or through consumption of heterotrophs, which would have been favoured by the high quantities of organic matter released during the bloom collapse.This work was funded by the EU project MABENE (grant: EKV3-2001-00144). I. G. T. was supported by a FCT (Portuguese Foundation for Science and Technology) doctoral fellowship (SFRH/BD/11309/2002) and B.G.C. by a CSIC-ESF I3P fellowship.Peer reviewe

Core research project: harmful algal blooms in upwelling systems

Global Ecology and Oceanography of Hatmful algal Blooms (GEOHAB): synthesis open science meeting, Paris, France, 24-26 April 2013The Core Research Project: HABs in upwelling systems was initiated by means of an Open Science Meeting in Portugal in November 2003. Eight key questions were formulated to address our understanding of the ecology and oceanography of HABs in upwelling systems. These questions related to the identification of adaptive strategies that characterize HAB species in upwelling systems, including seeding strategies, the influence of small-scale physical processes and nutrient supply in affecting HAB population dynamics, the role of genetic predisposition versus environmental conditions in toxin production, the influence of coastal morphology and bathymetry in determining the distribution of HABs, the relative importance of cross-shelf and along-shore advection for HABs, and the linkages of HAB events and climate. Following a comparative review of the ecology and oceanography of HABs in upwelling systems through publication of a special issue of Progress in Oceanography in 2010 we highlight further advances in addressing the above questions. We specifically examine achievements in terms of the overall goal of GEOHAB of prediction supported by observation and modelling systems. The comparative approach, as endorsed by GEOHAB, is considered to have added value to regional or national science programmes. Furthermore the CRP is deemed to have provided effective direction to HAB research in upwelling systems over the past decade which has improved the availability of comparable data. Prediction of HABs nevertheless remains limited by ecological complexity. However increasingly realistic hydrodynamic models with high spatial resolution now lay the groundwork for better prediction through incorporation of better resolved ecological properties and processesN