Benthic diatom monitoring and assessment of freshwater environments: standard methods and future challenges

Fil: Soizic, Morin. National Research Institute of Science and Technology for Environment and Agriculture; FranceFil: Gómez, Nora. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología Dr. Raúl A. Ringuelet; ArgentinaFil: Tornés, Elisabet. University of Girona. Institute of Aquatic Ecology; SpainFil: Licursi, Magdalena. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología Dr. Raúl A. Ringuelet; ArgentinaFil: Rosebery, Juliette. Aquatic Ecosystems and Global Changes Research Unit; Franc

Benthic diatom monitoring and assessment of freshwater environments: standard methods and future challenges

Fil: Soizic, Morin. National Research Institute of Science and Technology for Environment and Agriculture; FranceFil: Gómez, Nora. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología Dr. Raúl A. Ringuelet; ArgentinaFil: Tornés, Elisabet. University of Girona. Institute of Aquatic Ecology; SpainFil: Licursi, Magdalena. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología Dr. Raúl A. Ringuelet; ArgentinaFil: Rosebery, Juliette. Aquatic Ecosystems and Global Changes Research Unit; Franc

Dam regulation and riverine food-web sructure in a Mediterraenan river

Flow regimes are a major driver of community composition and structure in riverine ecosystems, and flow regulation by dams often induces artificially-stable flow regimes downstream. This represents a major source of hydrological alteration, particularly in regions where biota is adapted to strong seasonal and interannual flow variability. We hypothesized that dam-induced hydrological stability should increase the availability of autochthonous resources at the base of the food web. This, in turn, should favour herbivorous over detritivorous strategies, increasing the diversity of primary consumers, and the food-web width and length. We tested this hypothesis by studying the longitudinal variation in food-web structure in a highly-seasonal Mediterranean river affected by an irrigation dam. We compared an unregulated reach to several reaches downstream of the dam. Hydrological and sedimentological stability increased downstream of the dam, and altered the type and quantity of available resources downstream, prompting a change from a detritus-based to an algae-based food web. The fraction of links between top and intermediate species also increased, and the food web became longer and wider at the intermediate trophic levels. Food-web structure did not recover 14 km downstream of the dam, despite a partial restitution of the flow regime. Our results advance the notion that hydrologic alteration affects riverine food webs via additions/deletions of taxa and variation in the strength and distribution of food-web interactions. Thus, flow regulation by dams may not only impact individual facets of biodiversity, but also food-web level properties across river networks

Flow regulation increases food-chain length through omnivory mechanisms in a Mediterranean river network

[EN] Dams fragment river systems worldwide, and Mediterranean-climate rivers, characterised by highly seasonal hydrographs and adapted biotas, are particularly impacted by flow regulation. Whereas the effects of flow regulation on hydrology, sediment transport and biodiversity have long been examined, responses at the food-web level remain understudied. Environmental variation is a key control of food-web structure. Thus, we predicted that flow regulation would impact food-chain length (FCL) via changes in the flow variation regime, and we tested this prediction in a set of flow unregulated to completely regulated reaches in a Mediterranean river basin. In each reach, we characterised flow variation, together with two other putative controls of FCL (productivity and habitat size). We combined community data with carbon and nitrogen stable isotopes to estimate food-chain length, and Bayesian mixing models allowed estimates of dietary proportions of consumers. Flow variation was paramount in controlling FCL in the studied river network, and this same control largely explained the degree of omnivory among top predators. Thus, omnivory mechanisms were the main proximate structural mechanism allowing shifts in food-web structure and linking disturbance regimes to FCL. Our results suggest that flow regulation in Mediterranean rivers may impact food-web structure even when no significant changes in community composition are observed. If highly variable Mediterranean streams become increasingly affected by flow regulation, the resulting more stable conditions could enhance intraguild predation and thus lengthen riverine food chains.We thank Roberto Merciai, Jose Andres Lopez and Joan Font for their help in the field, Lina Ramirez-Solano and Emili Garcia-Berthou for their help with analyses and Marc Montenegro for the illustrations in Fig. 1. The Sabo Lab at Arizona State University and anonymous reviewers provided suggestions that improved the quality of the article. This study was funded by the Spanish Ministry of Economy and Competitiveness through the SCARCE project (CSD2009-00065). Authors acknowledge the support from the Catalan Government through the Consolidated Research Groups 'Fluvial Dynamics Research Group (2014 SGR 645)' and the 'Catalan Institute for Water Research (2014 SGR 291)'.Ruhí, A.; Muñoz, I.; Tornés, E.; Batalla, R.; Vericat, D.; Ponsati, L.; Acuña, V.... (2016). Flow regulation increases food-chain length through omnivory mechanisms in a Mediterranean river network. Freshwater Biology. 61(9):1536-1549. https://doi.org/10.1111/fwb.12794S1536154961

Distributional patterns of diatom communities in Mediterranean rivers

Aquesta tesi tracta la jerarquia i l'heterogeneïtat dels sistemes fluvials que afecten l'estructura de les comunitats bentòniques de diatomees. A nivell regional, es van buscar diferents grups de punts i les seves espècies indicadores, es va estudiar la resposta de les comunitats de diatomees als gradients ambientals, es va avaluar la utilitat de diferents índexs de diatomees i es va buscar el millor sistema de classificació per a condicions de referència. A nivell de conca, es volien definir els factors que determinen la distribució longitudinal de la diversitat de les comunitats de diatomees. Finalment, a nivell d'hàbitat es van determinar quins factors afecten les algues i els cianobacteris a aquesta escala i es va examinar la contribució relativa de l'ambient i l'espai en la distribució de la biomassa i composició d'algues i cianobacteris. Per tant, els diferents capítols d'aquesta tesi han estat desenvolupats seguint aquest esquema.This thesis deals with the hierarchy and heterogeneity of stream systems affecting the structure of benthic diatom communities. At a regional level, I search for different groups of sites and their indicator taxa, I studied the responses of the diatom communities to the gradients of environmental variables, I tested the usefulness of diatom indices and I searched for the best classification system for reference conditions. At a watershed level my interest was to define the factors that determined the longitudinal distribution of diversity of diatom communities. Finally, at a habitat level it was interesting to determine the factors affecting algae and cyanobacteria at this scale and examine the relative effects of environmental factors and space on the distribution of biomass and composition of benthic algae and cyanobacteria. Thus, the different chapters of the thesis had been approached following this scheme

Indicator taxa of benthic diatom communities: a case study in Mediterranean streams

A key issue in the implementation of the Water Framework Directive is the classification of streams and rivers using biological quality parameters and type-specific reference conditions. Four groups of stream types were defined in NE Spain on the basis of 152 diatom samples by means of detrended correspondence analysis and classification techniques. Diatom analysis was restricted to epilithic taxa, and the sites included gradients ranging from near-natural streams to sites with poor ecological quality. The main gradient shows a clear separation of sites in relation to the degree of human influence: polluted streams (mainly located in the lowlands) differ from streams in mountainous areas and in the Pyrenees. A second gradient is related to physiographical features. Headwater streams can be distinguished by their catchment geology. The type-specific diatom taxa for the stream types studied were determined by using indicator species analysis (IndVal). The type-specific taxa from near-natural streams are coincident with the indicator taxa for high ecological status. Human impact reduced the typological heterogeneity of the diatom community composition. Overall, the diatom communities in NE Spain exhibit a regional distribution pattern that closely corresponds with that observed in river systems elsewhere. Physiographical differences are only evident in undisturbed sites, while nutrient enrichment and other human disturbances may mask the regional differences in the distribution of diatom communitie

Dam regulation and riverine food-web sructure in a Mediterraenan river

Flow regimes are a major driver of community composition and structure in riverine ecosystems, and flow regulation by dams often induces artificially-stable flow regimes downstream. This represents a major source of hydrological alteration, particularly in regions where biota is adapted to strong seasonal and interannual flow variability. We hypothesized that dam-induced hydrological stability should increase the availability of autochthonous resources at the base of the food web. This, in turn, should favour herbivorous over detritivorous strategies, increasing the diversity of primary consumers, and the food-web width and length. We tested this hypothesis by studying the longitudinal variation in food-web structure in a highly-seasonal Mediterranean river affected by an irrigation dam. We compared an unregulated reach to several reaches downstream of the dam. Hydrological and sedimentological stability increased downstream of the dam, and altered the type and quantity of available resources downstream, prompting a change from a detritus-based to an algae-based food web. The fraction of links between top and intermediate species also increased, and the food web became longer and wider at the intermediate trophic levels. Food-web structure did not recover 14 km downstream of the dam, despite a partial restitution of the flow regime. Our results advance the notion that hydrologic alteration affects riverine food webs via additions/deletions of taxa and variation in the strength and distribution of food-web interactions. Thus, flow regulation by dams may not only impact individual facets of biodiversity, but also food-web level properties across river networks

Unravelling the effects of multiple stressors on diatom and macroinvertebrate communities in European river basins using structural and functional approaches

International audienceRivers suffer from more severe decreases in species diversity compared to other aquatic and terrestrial ecosys- tems due to a variety of pressures related to human activities. Species provide different roles in the functioning of the ecosystem, and their loss may reduce the capacity of the ecosystems to respond to multiple stressors. The effects on diversity will differ based on the type, combination and severity of stressors, as well as on the char- acteristics of the community composition and tolerance. Multiple trait-based approaches (MTBAs) can help to unravel the effects of multiple stressors on communities, providing a mechanistic interpretation, and, thus, complementing traditional biodiversity assessments using community structure. We studied the relationships between diversity indexes and trait composition of macroinvertebrate and diatom communities, as well as envi- ronmental variables that described the hydrological and geomorphological alterations and toxic pollution (pes- ticides and pharmaceuticals) of three different European river basins: the Adige, the Sava, and the Evrotas. These river basins can be considered representative cases of different situations in European freshwater systems. Hy- drological variables were the main drivers determining the community structure and function in the rivers, for both diatoms and macroinvertebrates. For diatom communities, pharmaceutical active compound (PhAC) toxic units were also identified as a very important driver of diversity changes, explaining up to 57% of the variance in taxonomic richness. For macroinvertebrates, river geomorphology was an important driver of structural changes, particularly affecting Plecoptera richness. In addition, PhAC and pesticide toxic units were also identified as stressors for macroinvertebrate communities. MTBA provided a detailed picture of the effects of the stressors on the communities and confirmed the importance of hydrological variables in shaping the functional attributes of the communities

Anàlisi de la viabilitat i proposta d’indicadors fitobentònics de la qualitat de l’aigua per als cursos fluvials de Catalunya: Aplicació de la Directiva Marc en Política d’Aigües de la Unió Europea (2000/60/CE)

El present treball forma part del conjunt de les tasques encomanades per l’Agència Catalana de l’Aigua (ACA) a diferents grups de recerca de les Universitats catalanes per tal d’aconseguir l’adequació a la Directiva Marc de l’ Aigua (en endavant DMA) aprovada per la Unió Europea al 2000. Un dels objectius de la DMA és promoure l’ús sostenible de l’aigua i té entre els objectius prioritaris mantenir i restaurar el bon estat ecològic dels ecosistemesaquàtics. Específicament la DMA demana procedir a l’efectiva protecció de les aigües superficials, dels estuaris, aigües costeres i subterrànies implicant en molts casos la reducció d’abocaments i contaminació a aquestes masses d’aigua.Els objectius del treball endegat amb les comunitats de diatomees són els següents: a. Diagnosi de la qualitat química i ecològica dels rius de les conques internes i de la part catalana de la conca de l’Ebre a partir de la informació proporcionada per la comunitat de diatomees; específicament, determinar quins punts tenen una qualitat molt dolenta, dolenta, mediocre, bona o excel·lent mitjançant l’ús de la informació proporcionada per les comunitats de diatomees. b. Determinar l’encaix de les comunitats de diatomees en la regionalització dels rius establerta des d’altres descriptors físics o biològics; en el seu cas, determinar quines regions són les que es poden establir directament a partir de la informació de les comunitats de diatomees. c. Avaluar la capacitat dels índexs de diatomees descrits per a d’altres situacions i països en la determinació de la qualitat de l’aigua i ecològica; determinar quin o quins són els índexs que millor descriuen la situació dels rius catalans; en el seu cas, perfilar les situacions en les que aquests índexs funcionen adequadament i en quines no ho fan; en el seu cas, suggerir possibles modificacions per tal d’adaptar-los a la realitat de les diferents ecoregions que es poden definir a Cataluny

Shared effects of organic microcontaminants and environmental stressors on biofilms and invertebrates in impaired rivers

Land use type, physical and chemical stressors, and organic microcontaminants were investigated for their effects on the biological communities (biofilms and invertebrates) in several Mediterranean rivers. The diversity of invertebrates, and the scores of the first principal component of a PCA performed with the diatom communities were the best descriptors of the distribution patterns of the biological communities against the river stressors. These two metrics decreased according to the progressive site impairment (associated to higher area of agricultural and urban-industrial, high water conductivity, higher dissolved organic carbon and dissolved inorganic nitrogen concentrations, and higher concentration of organic microcontaminants, particularly pharmaceutical and industrial compounds). The variance partition analyses (RDAs) attributed the major share (10%) of the biological communities' response to the environmental stressors (nutrients, altered discharge, dissolved organic matter), followed by the land use occupation (6%) and of the organic microcontaminants (2%). However, the variance shared by the three groups of descriptors was very high (41%), indicating that their simultaneous occurrence determined most of the variation in the biological communitiesThis study has been financially supported by the EU through the FP7 project GLOBAQUA (Grant agreement No 603629). The authors are part of the Consolidated Research Groups of the Generalitat de Catalunya (2014 SGR 291dICRA and 2014 SGR 418Water and Soil Quality Unit, IDAEA-CSIC