Annales De Limnologie-international Journal of Limnology, 2017
espanolLos ecosistemas fluviales tienen un papel relevante en los ciclos biogeoquimicos globales,... more espanolLos ecosistemas fluviales tienen un papel relevante en los ciclos biogeoquimicos globales, ya que procesan el material de la cuenca y lo transportan rio abajo. Sin embargo, los factores que afectan al metabolismo, especialmente aquellos que actuan en una escala espacial mas amplia, todavia no se conocen completamente. Ademas, el metabolismo fluvial puede variar a causa de cambios hidrologicos relacionados con la estacionalidad; lo que tambien hace importante incluir la variabilidad temporal para entender el funcionamiento de los rios. Mediante el uso de un experimento distribuido y coordinado, estudiamos diez rios de cabecera localizados a lo largo de cinco ecoregiones europeas durante verano y otono del 2014. Se midio la magnitud y la variabilidad de la produccion primaria bruta (PPB) y la respiracion ecosistemica (RE) mediante el metodo de canal abierto. Asi mismo, se examinaron los factores climaticos, hidrologico s y fisico-quimicos que potencialmente pueden afectar las t...
Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majorit... more Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1 mmol m−2 h−1 at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams.
The sensitivity and spatial recovery of river sediment biofilms along 1 km after the input of two... more The sensitivity and spatial recovery of river sediment biofilms along 1 km after the input of two wastewater treatment plants (WWTPs) located in two river reaches with different degrees of anthropogenic influence were investigated. First, at the upper reach, we observed an inhibition of some microbial functions (microbial respiration and extracellular enzyme activities) and strong shifts in bacterial community composition (16S rRNA gene), whereas an increase in microbial biomass and activity and less pronounced effect on microbial diversity and community composition were seen at the lower reach. Second, at the lower reach we observed a quick spatial recovery (around 200 m downstream of the effluent) as most of the functions and community composition were similar to those from reference sites. On the other hand, bacterial community composition and water quality at the upper reach was still altered 1 km from the WWTP effluent. Our results indicate that biofilms in the upstream sites w...
Temporary streams are submitted to high seasonal hydrological variations which induce habitat fra... more Temporary streams are submitted to high seasonal hydrological variations which induce habitat fragmentation. Global change promotes longer non-flow periods, affecting hydrological continuity and the distribution of biological assemblages in river networks. We aimed to investigate the effects of hydrological discontinuity on phototrophic biofilm assemblages in a Mediterranean stream, at both network and habitat scales. At the network scale during basal flow conditions, mostly nitrate and DOC concentrations were associated to the taxonomical and trait distribution of algae and cyanobacterial assemblages. Cyanobacteria dominated at the upstream and downstream sites of the network, while green algae and diatoms were abundant in its middle part. At the habitat scale, hydrological discontinuity promoted large changes in biofilm composition between riffles and pools, where pools were inhabited preferentially by green algae and riffle habitats by cyanobacteria. Our findings emphasize the my...
Global change exposes ecosystems to a myriad of stressors differing in their spatial (i.e. surfac... more Global change exposes ecosystems to a myriad of stressors differing in their spatial (i.e. surface of stressed area) and temporal (i.e. exposure time) components. Among freshwater ecosystems, rivers and streams are subject to physical, chemical and biological stressors, which interact with each other and might produce diverging effects depending on exposure time. We conducted a manipulative experiment using 24 artificial streams to examine the individual and combined effects of warming (1.6 °C increase in water temperature), hydrological stress (simulated low-flow situation) and chemical stress caused by pesticide exposure (15.1–156.7 ng L−1) on river biofilms. We examined whether co-occurring stressors could lead to non-additive effects, and if these differed at two different exposure times. Specifically, structural and functional biofilm responses were assessed after 48 hours (short-term effects) and after 30 days (long-term effects) of exposure. Hydrological stress caused strong ...
Coordinated distributed experiments (CDEs) allow the study of large-scale ecological patterns in ... more Coordinated distributed experiments (CDEs) allow the study of large-scale ecological patterns in geographically dispersed areas, providing at the same time broad benefits for the participants. However, the effective involvement of early-stage career researchers (ECRs) confronts major challenges. Here, we analyze the benefits and challenges of the first CDE exclusively leaded and conducted by ECRs (i.e. ECR-CDE), that set the basis for similar CDEs and provide recommendations for their successful development. We recognize that ECR-CDEs embrace most of the outcomes identified in common CDEs as well as extended benefits for the young cohort of researchers, including: (i) scientific credit, (ii) peer-training in new concepts and methods, (iii) developing leadership and communication skills, (iv) promoting a peer network among ECRs, and (v) building on individual engagement and independency. We also discuss ECR-CDEs challenges, which are mainly derived from the lack of independence and s...
Annales De Limnologie-international Journal of Limnology, 2017
espanolLos ecosistemas fluviales tienen un papel relevante en los ciclos biogeoquimicos globales,... more espanolLos ecosistemas fluviales tienen un papel relevante en los ciclos biogeoquimicos globales, ya que procesan el material de la cuenca y lo transportan rio abajo. Sin embargo, los factores que afectan al metabolismo, especialmente aquellos que actuan en una escala espacial mas amplia, todavia no se conocen completamente. Ademas, el metabolismo fluvial puede variar a causa de cambios hidrologicos relacionados con la estacionalidad; lo que tambien hace importante incluir la variabilidad temporal para entender el funcionamiento de los rios. Mediante el uso de un experimento distribuido y coordinado, estudiamos diez rios de cabecera localizados a lo largo de cinco ecoregiones europeas durante verano y otono del 2014. Se midio la magnitud y la variabilidad de la produccion primaria bruta (PPB) y la respiracion ecosistemica (RE) mediante el metodo de canal abierto. Asi mismo, se examinaron los factores climaticos, hidrologico s y fisico-quimicos que potencialmente pueden afectar las t...
Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majorit... more Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1 mmol m−2 h−1 at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams.
The sensitivity and spatial recovery of river sediment biofilms along 1 km after the input of two... more The sensitivity and spatial recovery of river sediment biofilms along 1 km after the input of two wastewater treatment plants (WWTPs) located in two river reaches with different degrees of anthropogenic influence were investigated. First, at the upper reach, we observed an inhibition of some microbial functions (microbial respiration and extracellular enzyme activities) and strong shifts in bacterial community composition (16S rRNA gene), whereas an increase in microbial biomass and activity and less pronounced effect on microbial diversity and community composition were seen at the lower reach. Second, at the lower reach we observed a quick spatial recovery (around 200 m downstream of the effluent) as most of the functions and community composition were similar to those from reference sites. On the other hand, bacterial community composition and water quality at the upper reach was still altered 1 km from the WWTP effluent. Our results indicate that biofilms in the upstream sites w...
Temporary streams are submitted to high seasonal hydrological variations which induce habitat fra... more Temporary streams are submitted to high seasonal hydrological variations which induce habitat fragmentation. Global change promotes longer non-flow periods, affecting hydrological continuity and the distribution of biological assemblages in river networks. We aimed to investigate the effects of hydrological discontinuity on phototrophic biofilm assemblages in a Mediterranean stream, at both network and habitat scales. At the network scale during basal flow conditions, mostly nitrate and DOC concentrations were associated to the taxonomical and trait distribution of algae and cyanobacterial assemblages. Cyanobacteria dominated at the upstream and downstream sites of the network, while green algae and diatoms were abundant in its middle part. At the habitat scale, hydrological discontinuity promoted large changes in biofilm composition between riffles and pools, where pools were inhabited preferentially by green algae and riffle habitats by cyanobacteria. Our findings emphasize the my...
Global change exposes ecosystems to a myriad of stressors differing in their spatial (i.e. surfac... more Global change exposes ecosystems to a myriad of stressors differing in their spatial (i.e. surface of stressed area) and temporal (i.e. exposure time) components. Among freshwater ecosystems, rivers and streams are subject to physical, chemical and biological stressors, which interact with each other and might produce diverging effects depending on exposure time. We conducted a manipulative experiment using 24 artificial streams to examine the individual and combined effects of warming (1.6 °C increase in water temperature), hydrological stress (simulated low-flow situation) and chemical stress caused by pesticide exposure (15.1–156.7 ng L−1) on river biofilms. We examined whether co-occurring stressors could lead to non-additive effects, and if these differed at two different exposure times. Specifically, structural and functional biofilm responses were assessed after 48 hours (short-term effects) and after 30 days (long-term effects) of exposure. Hydrological stress caused strong ...
Coordinated distributed experiments (CDEs) allow the study of large-scale ecological patterns in ... more Coordinated distributed experiments (CDEs) allow the study of large-scale ecological patterns in geographically dispersed areas, providing at the same time broad benefits for the participants. However, the effective involvement of early-stage career researchers (ECRs) confronts major challenges. Here, we analyze the benefits and challenges of the first CDE exclusively leaded and conducted by ECRs (i.e. ECR-CDE), that set the basis for similar CDEs and provide recommendations for their successful development. We recognize that ECR-CDEs embrace most of the outcomes identified in common CDEs as well as extended benefits for the young cohort of researchers, including: (i) scientific credit, (ii) peer-training in new concepts and methods, (iii) developing leadership and communication skills, (iv) promoting a peer network among ECRs, and (v) building on individual engagement and independency. We also discuss ECR-CDEs challenges, which are mainly derived from the lack of independence and s...
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Papers by Anna Freixa