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

Bacterioplankton responses to riverine and atmospheric inputs in a coastal upwelling system (Ría de Vigo, NW Spain)

Original research paperAnthropogenic pressures are changing the magnitude and nature of matter inputs into the ocean. The Ría de Vigo (NW Spain) is a highly productive and dynamic coastal system that is likely affected by such alterations. Previous nutrient-addition microcosm experiments conducted during contrasting hydrographic conditions suggested that heterotrophic bacteria are limited by organic carbon (C) and occasionally co-limited by inorganic nutrients in this coastal area. In order to assess short-term responses in biomass, production, and respiration of heterotrophic bacteria from the Ría de Vigo to increasing amounts of natural inputs of matter, we conducted 6 microcosm experiments, wherein surface seawater collected in spring, summer, and autumn was mixed with increasing amounts of dissolved natural matter concentrates from riverine and atmospheric origin. Simultaneous experiments with controlled inorganic and/or organic additions indicated that bacteria were co-limited by inorganic nutrients and C in spring and summer and primarily limited by C in autumn. Production responded more than biomass to increasing inputs of matter, whereas respiration did not change. The bacterial production response to increasing dissolved organic C load associated with riverine and atmospheric inputs was strongly related to the relative phosphorus (P) content of the dissolved matter concentrates. Our data suggest that bacterial production might decrease with the increase of P-deficient allochthonous matter inputs, which would have important biogeochemical consequences for C cycling in coastal areas.Spanish Ministry of Science and Innovation, MINECO, CSIC, Xunta of Galicia and European Union (Marie Curie Grants)Versión del edito

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

Publicado

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

Publicado

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

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Advection, diffusion and patch development in the rias Baixas

6 pages, 3 figures, 2 tablesThis work was supported by the EC MAST-CT90-0017 on the Control of the Phytoplankton DominanceN

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

Physical–biological coupling in the coastal upwelling system of the Ría de Vigo (NW Spain). I: In situ approach

Original research articleThe fate of the inorganic and organic nitrogen trapped in the coastal upwelling system of Ría de Vigo (NW Spain) was studied at the 2 to 4 d time-scale during July and September 2002. A transient geochemical model was applied to the measured residual currents and concentrations of inorganic nitrogen (NT), and dissolved (DON) and particulate (PON) organic N to obtain (1) the net balance of inputs minus outputs (i – o); (2) the net accumulation; and (3) the net ecosystem production (NEP) of NT, DON and PON. Previously unaccounted lateral variations in residual currents and N species concentrations in the ría were considered. The ría was autotrophic during July (average NEP, 107 mg N m–2 d–1). About 25% of this material was exported to the shelf and the remaining 75% was transferred to the sediments or promoted to higher trophic levels. During summer upwelling episodes, 30 to 70% of the organic N exported to the shelf came from materials previously accumulated in the ría. By contrast, during summer relaxation, 60 to 70% of the accumulated organic N came from in situ conversion of NT and the remaining 30 to 40% was allochthonous. As shown by other authors, NEP was rather low during intense upwelling and increased to high values during its subsequent relaxation. In September, the metabolism changed from heterotrophic to slightly autotrophic (average NEP, 26 mg N m–2 d–1). The DON and PON imported from the shelf during autumn downwelling experienced a different fate: DON was consumed and PON accumulated in the ría. By contrast, DON and PON were produced in situ at the expense of N nutrients previously accumulated into the system during autumn relaxation. The roles of vertical convection and turbulent mixing in the fertilization of the photic layer were also assessed. Mixing was the most important fertilization mechanism, ensuring transport of nutrients under upwelling and downwelling conditions.The Spanish Ministerio de Educación y Ciencia (MEC), grant nos. REN2000-0880-C02-01 and -02 and the Xunta de Galicia grant no. PGIDT01MAR40201PN. This is contribution no. 39 of the Unidad Asociada GOFUVICSIC and predoctoral fellowships from the MEC and postgraduate fellowships from the CSIC-I3P programme and postdoctoral programme ‘Parga Pondal’ of the ‘Xunta de Galicia"Versión del edito