Does grazing pressure modify diuron toxicity in a biofilm community?

Herbicides affect the structure and functional parameters of fluvial biofilm. Diuron is toxic to primary producers and disrupts endocrine activity. Here, we studied the interaction between this toxicant and several biological compartments in a simple food chain composed of herbivores (the snail Physella [Costatella] acuta) and biofilm. We used indoor experimental channels to which Diuron was added at a realistic concentration (2 μg/L). Bacterial survival and chlorophyll-a and photosynthetic activity were analyzed in the biofilm. We monitored biomass, mortality, reproduction, and motility as end points in the freshwater snail P. acuta. Our results showed that bacterial survival and photosynthetic activity were sensitive to Diuron. Snails were not affected by the herbicide at the concentration tested. No significant interactions between the toxicant and grazers were observed on the biofilm. Reproductive traits, however, were slightly affected, indicating a possible endocrine disruption

Bridging levels of pharmaceuticals in river water with biological community structure in the Llobregat river basin (NE Spain)

A wide range of human pharmaceuticals are present at low concentrations in freshwater systems, particularly in sections of polluted river. These compounds show high biological activity, often associated with a high stability. These characteristics imply a potential impact of these substances on aquatic biota even when present at low environmental concentrations. Low flow conditions in Mediterranean rivers, most of which flow through densely populated areas and are subjected to intensive water use, increase the environmental risk of these emergent compounds. Here, we studied whether pharmaceuticals in river water affect the local benthic community structure (diatoms and invertebrates). For this purpose, we analyzed the occurrence of pharmaceuticals along the Llobregat River and examined the benthic community structure (diatoms and invertebrates) of this system. Some pharmaceutical products in the Llobregat River registered concentrations greater than those cited in the literature. Multivariate analyses revealed a potential causal association between the concentrations of some anti-inflammatories and β-blockers and the abundance and biomass of several benthic invertebrates (Chironomus spp. and Tubifex tubifex). Further interpretation in terms of cause-and-effect relationships is discussed; however, it must be always taken with caution because other pollutants also may have significant contributions. Combined with further community experiments in the laboratory, our approach could be a desirable way to proceed in future risk management decisions

Uso de ríos artificiales en ecología fluvial

Capítol 21 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix a la utilització dels rius artificials en ecologia fluvialPodeu consultar el llibre complet a: http://www.fbbva.es/TLFU/microsites/ecologia_fluvial/index.ht

Flujo de energía en el ecosistema fluvial : análisis del metabolismo

Capítol 20 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix al metabolisme fluvialPodeu consultar el llibre complet a: http://www.fbbva.es/TLFU/microsites/ecologia_fluvial/index.ht

Catalase in fluvial biofilms: a comparison between different extraction methods and example of application in a metal-polluted river

Antioxidant enzymes are involved in important processes of cell detoxification during oxidative stress and have, therefore, been used as biomarkers in algae. Nevertheless, their limited use in fluvial biofilms may be due to the complexity of such communities. Here, a comparison between different extraction methods was performed to obtain a reliable method for catalase extraction from fluvial biofilms. Homogenization followed by glass bead disruption appeared to be the best compromise for catalase extraction. This method was then applied to a field study in a metal-polluted stream (Riou Mort, France). The most polluted sites were characterized by a catalase activity 4–6 times lower than in the low-polluted site. Results of the comparison process and its application are promising for the use of catalase activity as an early warning biomarker of toxicity using biofilms in the laboratory and in the fiel

Diatom responses to zinc contamination along a Mediterranean river

Background and aims – Diatom-based water quality management is increasing, and specific indicators are required for the assessment of priority substances such as metals. We tested a variety of features of diatom communities, in a river exhibiting a gradient of zinc contamination (the Riera d’Osor, Spain), to determine the most relevant ones. Key results – Community composition changed over time of exposure, and with the intensity of metal contamination. Species richness was significantly lower at the most contaminated sites. Species composition was more even under background and low exposure levels, but low metal inputs selected for varieties of Cocconeis placentula (var. placentula, euglypta and lineata). Small taxa (Eolimna minina, or Achnanthidium minutissimum and A. pyrenaicum) dominated in the most contaminated sites, and deformed diatom cells were found abundant. Conclusions – Although species composition clearly responded to varied levels of zinc pollution, combining cell size classes or total biovolume of the community and percentages of deformities allowed reliable assessment of the presence, and intensity, of contamination. These descriptors present the major advantage of being independent of regional taxonomic peculiarities, thus providing robust assessment irrespective of the area studiedSilvia Corcoll kindly mapped the Riera d’Osor watershed. The study was partially by the European project Keybioeffects (MRTN-CT-2006-035695) and the Spanish project FLUVIALMULTISTRESS (CTM2009-14111-C02-01

Hydrology, light and the use of organic and inorganic materials as structuring factors of biological communities in Mediterranean streams

Hydrological disturbances, light availability and nutrients are the most relevant factors determining the structure of the biological communities in Mediterranean rivers. While some hydrological disturbances are able to induce catastrophic effects, which may cause a complete reset in physical and biological conditions, continued enrichment or changes in light availability are factors leading to the progressive shift in the communities of autotrophs and heterotrophs in the systems. Primary production in Mediterranean streams shows relevant seasonal changes which mainly follows the variations in light availability. In most forested streams, the algal community is shade-adapted. Nutrient enrichment (especially phosphorus) leads to marked increases in primary production, but this increase is not lineal and there is a saturation of algal biomass even in the most enriched systems. The heterotrophs (bacteria, fungi) are related to the pattern of DOC availability (which most depends on the seasonal discharge and leaf fall dynamics) and to the available substrata in the stream. It has been repeatedly observed that shorttime increases of extracellular enzyme activities are related to the accumulation of autochthonous (algal) and/or allochthonous (leaves) organic matter on the streambed during spring and summer, this being more remarkable in dry than in wetter years. Flow reduction favours detritus concentration in pools, and the subsequent increase in the density and biomass of the macroinvertebrate community. In Mediterranean streams collectors are accounting for the highest density and biomass, this being more remarkable in the least permanent systems, in accordance with the effect of floods on the organic matter availability. Nutrients, through the effect on the primary producers, also affect the trophic food web in the streams by favouring the predominance of grazersLos cambios hidrológicos, la disponibilidad de la luz y los nutrientes son los factores más importantes que determinan la estructura y función de la comunidad en los ríos Mediterráneos. Mientras los cambios hidrológicos pueden causar un total reestablecimiento en las condiciones físicas y biológicas, un aumento continuo de la concentración de nutrientes o cambios en la disponibilidad de la luz, son factores que favorecen un cambio progresivo de las comunidades de autótrofos y heterótrofos. La producción primaria en los ríos Mediterráneos presenta cambios estacionales en función de la luz. En los ríos forestados, las algas están adaptadas a la baja intensidad de la luz. El aumento de la concentración de nutrientes, especialmente el fósforo, favorece la producción primaria pero no de forma lineal, ya que aparece una saturación de la biomasa algal en los sistemas más eutróficos. Los heterótrofos (bacterias y hongos) están más relacionados con la disponibilidad de DOC (que a su vez depende de las variaciones estacionales del caudal y de la dinámica de la caída de las hojas) y de sustrato. Se ha observado, repetidamente, una relación entre el aumento a corto plazo de la actividad exoenzimática y la acumulación de biomasa autóctona algal y/o alóctona (hojas) en el lecho del río, durante la primavera y el verano. Esta relación es más evidente en los años más secos. La reducción del caudal favorece la concentración del detritus en las áreas de menor velocidad de corriente ('pools') y se observa un aumento en la densidad y biomasa de los macroinvertebrados. En los ríos Mediterráneos los recolectores alcanzan las mayores densidades y biomasas, especialmente en los sistemas menos permanentes, en relación con el efecto de las variaciones de caudal sobre la disponibilidad de materia orgánica. Los nutrientes, a través de la producción primaria, tienen un efecto también sobre la estructura de la red trófica, favoreciendo a los ramoneadore

Diatom responses to zinc contamination along a Mediterranean river

Background and aims – Diatom-based water quality management is increasing, and specific indicators are required for the assessment of priority substances such as metals. We tested a variety of features of diatom communities, in a river exhibiting a gradient of zinc contamination (the Riera d’Osor, Spain), to determine the most relevant ones. Key results – Community composition changed over time of exposure, and with the intensity of metal contamination. Species richness was significantly lower at the most contaminated sites. Species composition was more even under background and low exposure levels, but low metal inputs selected for varieties of Cocconeis placentula (var. placentula, euglypta and lineata). Small taxa (Eolimna minina, or Achnanthidium minutissimum and A. pyrenaicum) dominated in the most contaminated sites, and deformed diatom cells were found abundant. Conclusions – Although species composition clearly responded to varied levels of zinc pollution, combining cell size classes or total biovolume of the community and percentages of deformities allowed reliable assessment of the presence, and intensity, of contamination. These descriptors present the major advantage of being independent of regional taxonomic peculiarities, thus providing robust assessment irrespective of the area studiedSilvia Corcoll kindly mapped the Riera d’Osor watershed. The study was partially by the European project Keybioeffects (MRTN-CT-2006-035695) and the Spanish project FLUVIALMULTISTRESS (CTM2009-14111-C02-01

Mutual interaction between Arsenic and biofilm in a mining impacted river

Gold mining activities in fluvial systems may cause arsenic (As) pollution, as is the case at the Anllóns River (Galicia, NW Spain), where high concentrations of arsenate (AsV) in surface sediments (up to 270 mg kg−1) were found. A 51 day-long biofilm-translocation experiment was performed in this river, moving some biofilm-colonized substrata from upstream (less As-polluted) to downstream the mine area (more As-polluted site), to explore the effect of As on benthic biofilms, as well as their role on As retention and speciation in the water-sediment interface. Eutrophic conditions (range: 0.07-0.38 mg L−1 total phosphorus, TP) were detected in water in both sites, while sediments were not considered P-polluted (below 600 mg kg−1). Dimethylarsenate (DMAV) was found intracellularly and in the river water, suggesting a detoxification process by biofilms. Since most As in sediments and water was AsV, the high amount of arsenite (AsIII) detected extracellularly may also confirm AsV reduction by biofilms. Furthermore, translocated biofilms accumulated more As and showed higher potential toxicity (higher As/P ratio). In concordance, their growth was reduced to half that observed in those non-translocated, became less nutritive (less nitrogen content), and with higher bacterial and dead diatom densities. Besides the high As exposure, other environmental conditions such as the higher riparian cover at the more As-polluted site could contribute to those effects. Our study provides new arguments to understand the contribution of microorganisms to the As biogeochemistry in freshwater environment

La biota de los ríos : los microorganismos autótrofos

Capítol 12 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix als microorganismes autòtrofes dels sistemes fluvialsPodeu consultar el llibre complet a: http://www.fbbva.es/TLFU/microsites/ecologia_fluvial/index.ht