Downstream changes in spring-fed stream invertebrate communities: The effect of increased temperature range?

ABSTRACT: Reduced thermal amplitude has been highlighted as a limiting factor for aquatic invertebrate diversity in springs. Moving downstream water temperature range increases and invertebrate richness is expected to change accordingly. In the present study temperature patterns were investigated in seven spring-fed streams, between April 2001 and November 2002, and compared to five run-off-fed streams to assess the degree of crenic temperature constancy. Temperature and physico-chemical characteristics of the water, and food resource levels were measured, and the invertebrate fauna collected at 4 distances (0, 100, 500 m and 1 km) from seven springs in the North and South Islands of New Zealand. Temperature variability was greater for run-off-fed streams than for springs, and increased in the spring-fed streams with distance from the source. Periphyton and physico-chemical characteristics of the water did not change markedly over the 1 km studied, with the exception of water velocity and organic matter biomass, which increased and decreased, respectively. The rate of increase in temperature amplitude differed greatly for the studied springs, probably being affected by flow, altitude, and the number and type of tributaries (i.e., spring- or run-off-fed) joining the spring-fed stream channel. Longitudinal changes in the number and evenness of invertebrate taxa were positively correlated to thermal amplitude (rs = 0.8). Moving downstream, invertebrate communities progressively incorporated taxa with higher mobility and taxa more common in nearby run-off-fed streams. Chironomids and non-insect taxa were denser at the sources. Chironomid larvae also numerically dominated communities 100 and 500 m downstream from the sources, together with Pycnocentria spp. and Zelolessica spp., while taxa such as Hydora sp. and Hydraenidae beetles, the mayflies Deleatidium spp. and Coloburiscus humeralis, and the Trichoptera Pycnocentrodes spp., all had greater abundances 1 km from the sources. In conclusion, water temperature range was highly correlated with number of taxa, although other factors, such as substratum composition, stability and invertebrate drift, may also play an important role in the determination of longitudinal changes in invertebrate community composition and structure along spring-fed streams.We are grateful to Kirsty Francis and the postgraduate students in the Ecology Department, Massey University, for assistance in the field and in the lab. We are also thankful to Pablo Barquín, Lucía Creste, and Kyrin Weaver for help with bug sorting, and to Fiona Death for editing the manuscript. We would also like to thank to two anonymous reviewers for comments that greatly improved the paper. This research was supported by a scholarship from the Department of Education, Universities and Research of the Basque Government

A comparison of modeling techniques to predict hydrological indices in ungauged rivers

Predicting the natural flow regime in ungauged rivers is an important challenge in water resource management and ecological research. We developed models to predict 16 hydrological indices in a river network covering the northern third of the Iberian Peninsula. Multiple Linear Regression (MLR), Generalized Additive Models (GAMs), Random Forest (RF) and Adaptive Neuro Fuzzy Inference System (ANFIS) were used and compared according to their prediction accuracy. The results showed that predictive performance varied greatly depending on the modeled hydrological attribute. The magnitude and frequency indices were predicted with excellent accuracy. In contrast, no technique was capable of developing precise models for hydrological indices of timing, duration and rate of change. This is mainly related to the lack of proper environmental databases on the scales on which these flow regime patterns are influenced. In addition, complex modeling techniques did not always outperform linear models and no single approach was optimal for all indices. ANFIS and GAMs provided the best results; however, other issues such as computational cost and the level of knowledge required to apply the method and interpret the results should be taken into account.This study was partly funded by the Spanish Ministry of Economy and Competitiveness as part of the HYDRA (Ref. BIA2015-71197) and RIVERLANDS (Ref. BIA2012-33572) projects

Large-scale spatial patterns of riverine communities: niche versus geographical distance

Freshwater ecosystems are among the most threatened ecosystems on Earth. Effective conservation strategies are essential to reverse this trend and should be based on sound knowledge of biodiversity patterns and the main drivers structuring them. In this study, we investigated the role of environmental and dispersal-connectivity controls on freshwater diatom and fish communities? variability. We used 441 biological samples obtained from Spanish biomonitoring datasets, which cover a highly variable environmental gradient across the national river network. We compared the taxonomic and trait-based spatial dependency of the two biotic groups using distance-decay relationships and variation partitioning with spatially constrained randomisations. Our findings showed that most of the diatoms and fish biological variation was attributed to pure spatial and spatially structured environmental variation. Compared to diatoms, fish community composition presented a stronger spatial dependency, likely because of their weaker dispersal ability. In addition, broad-scale environmental characteristics showed a higher predictive capacity for fish assemblages? variation. Trait-based similarities presented lower spatial dependency than taxonomic datasets, indicating that they are less susceptible to dispersal-connectivity effects. These findings contribute to understand the mechanisms underlying river community assembly at large spatial scales (i.e., at and beyond the river network) and point out the importance of dispersal-connectivity processes, which are usually neglected in traditional niche-based biomonitoring programmes but can influence their outcomes (e.g., masking the detection of anthropogenic impacts). Therefore, the integration of the dispersal-connectivity component, as well as information on organisms? dispersal abilities, are crucial when establishing effective conservation objectives and designing biomonitoring strategies.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No 765553 and from the project “WATERLANDS”, code PID2019-107085RB-I00, funded by MCIN/AEI/10.13039/501100011033/ and by ERDF “A way of making Europ

Applying Optimization to Support Adaptive Water Management of Rivers

ABSTRACT: Adaptive water management is a promising management paradigm for rivers that addresses the uncertainty of decision consequences. However, its implementation into current practice is still a challenge. An optimization assessment can be framed within the adaptive management cycle allowing the definition of environmental flows (e-flows) in a suitable format for decision making. In this study, we demonstrate its suitability to mediate the incorporation of e-flows into diversion management planning, fostering the realization of an adaptive management approach. We used the case study of the Pas River, Northern Spain, as the setting for the optimization of surface water diversion. We considered e-flow requirements for three key river biological groups to reflect conditions that promote ecological conservation. By drawing from hydrological scenarios (i.e., dry, normal, and wet), our assessment showed that the overall target water demand can be met, whereas the daily volume of water available for diversion was not constant throughout the year. These results suggest that current the decision making needs to consider the seasonal time frame as the reference temporal scale for objectives adjustment and monitoring. The approach can be transferred to other study areas and can inform decision makers that aim to engage with all the stages of the adaptive water management cycle

The effect of altered flow regimes on aquatic primary producer communities: Diatoms and macrophytes

Rivers are intensively managed worldwide through unprecedented flow regime alterations on a global scale. This has led to an increasing interest in the development of quantitative tools to assess the ecological response of organisms to flow alteration. To date, studies reflect a large diversity of responses that make the intensity and prevalence of effects difficult to generalize. The present study analysed how flow alterations caused by dams affect the structure, composition and traits of diatoms and macrophytes in three Spanish river basins (Cantabric, Ebro and Duero). By using a control-impact design based mainly in hydrological similarity, our results showed consistent patterns of change in diatom and macrophyte communities. Our study showed a shift from resistant traits such as non-colonial diatom forms and crust-forming algae, which are adapted to the extreme events and natural dynamism of unregulated rivers, towards planktonic diatoms, free-floating algae and the mass development of aquatic plants in hydrological altered sites. Both communities shared common thresholds of response to altered hydrological attributes that could be considered in a flow management context. The hydrological indices that impacted diatom and macrophyte communities the most were related with the magnitude and duration of minimum flows. However, our results also show that it is important to consider the interrelationships between the different hydrological attributes such as the seasonal variability of monthly flows, the magnitude of maximum annual extremes, the timing of flow events, and the frequency and rate of flow changes.This study was funded by the Spanish Ministry of Economy and Competitiveness as part of the HYDRA (ref. BIA2015-71197) project and by the European Commission, Horizon 2020 Framework Programme, Marie Skłodowska-Curie Innovative Training Network 765553 as part of EUROFLOW project. We thank our colleagues from IHCantabria for the great help provided during fieldwork. We would also like to thank the Spanish Ministry of Public Works and the Ministry for the Ecological Transition for providing flow series data. Cristina Delgado was financially supported by postdoctoral grant I2C-B from the Xunta de Galicia government (Galicia, Spain)

Quantifying the performance of automated GIS-based geomorphological approaches for riparian zone delineation using digital elevation models

ABSTRACT: Riparian zone delineation is a central issue for managing rivers and adjacent areas; however, criteria used to delineate them are still under debate. The area inundated by a 50-yr flood has been indicated as an optimal hydrological descriptor for riparian areas. This detailed hydrological information is usually only available for populated areas at risk of flooding. In this work we created several floodplain surfaces by means of two different GIS-based geomorphological approaches using digital elevation models (DEMs), in an attempt to find hydrologically meaningful potential riparian zones for river networks at the river basin scale. Objective quantification of the performance of the two geomorphologic models is provided by analysing coinciding and exceeding areas with respect to the 50-yr flood surface in different river geomorphological types

Riparian quality and habitat heterogeneity assessment in Cantabrian rivers

RESUMEN. En este estudio se intentó evaluar la calidad riparia y la heterogeneidad del hábitat fluvial Como parte de la evaluación del estado de conservación de la Directiva Hábitats (CE, 1992) en los ríos incluidos en la red Natura 2000 de Cantabria, norte de España. Entre los métodos existentes elegimos los ´índices Qualitat del Bosc de Ribera (QBR) y “Riparian Quality Index” (RQI) para evaluar la calidad de la ribera, y el ´Indice de Habitabilidad fluvial (IHF) y el “Habitat Quality Assessment” (HQA) para evaluar la heterogeneidad del hábitat fluvial. El presente estudio pretende comparar el rendimiento del QBR y RQI para evaluar la calidad ribereña (RQ) y del IHF y HQA para evaluar la heterogeneidad del hábitat fluvial (RHH). Cuanto mayor sea la puntuación de los ´índices en un tramo de rio, más alta es la probabilidad de que Pertenezca a una condición de referencia, y también de que alcance una mayor integridad biológica. Por lo tanto, se utilizó la regresión logística binaria elaborando un modelo para RQ y otro para RHH, con el fin de examinar las relaciones entre los atributos evaluados por cualquiera de los cuatro ´índices y las condiciones de referencia y de no-referencia. También nos fijamos en las relaciones entre RQ y RHH y de ambos con las comunidades de macroinvertebrados. Se muestrearon la vegetación ribereña y las características del hábitat fluvial en un total de 285 tramos de 500 metros de longitud a lo largo de la red fluvial de Cantabria. Estos datos fueron comparados con datos existentes sobre la comunidad de macroinvertebrados en un total de 52 tramos de ríos y la métrica IASPT se calculó para las comparaciones. En este estudio, las condiciones de referencia se fijaron en 10 tipologías fluviales de acuerdo a los siguientes criterios: (1) régimen hidrológico inalterado, (2) usos del suelo no intensivos y (3) sin presencia o mínimos cambios morfológicos, terminando con un total de 96 tramos de río seleccionados. QBR y RQI fueron sensibles a las condiciones de referencia y a las tipologías fluviales, siendo mayor en condiciones de referencia en la mayoría de los tipos fluviales. Sin embargo, IHF y HQA sólo presentaron diferencias dependiendo del tipo fluvial y no en función de las condiciones de referencia. Por otra parte, IHF y HQA no tienen una respuesta similar a la modificación humana en todas las tipologías de río, ya que los tramos en condiciones de referencia presentaron valores más altos o más bajos que los tramos en condiciones de no-referencia en función de las tipologías fluviales. Por último, RQ se correlacionó positivamente con RHH, y el IASPT aumentó con ambos. Llegamos a la conclusión de que RQI y HQA obtuvieron ligeramente mejores resultados que el QBR y IHF para distinguir entre sitios en condiciones de referencia y no referencia en los ríos de Cantabria, y que la heterogeneidad del hábitat fluvial no debe ser utilizada para evaluar la calidad del hábitat fluvial.ABSTRACT. In this study, we attempted to assess riparian quality and river habitat heterogeneity as part of the conservation status assessment of the Habitats Directive (EC, 1992) in the rivers included in the Nature 2000 network of Cantabria, Northern Spain. We chose the Qualitat del Bosc de Ribera (QBR) and the Riparian Quality Index (RQI) to assess riparian quality and the ´Indice de Habitabilidad Fluvial (IHF) and Habitat Quality Assessment (HQA) to assess the river habitat heterogeneity. The present study aims to compare the performance of the QBR and RQI for assessing riparian quality (RQ) and of the IHF and HQA for assessing river habitat heterogeneity (RHH). With a higher score in each index, the site has a higher likelihood of belonging to a reference condition and also of reaching a higher biological integrity. Thus, we used logistic binary regressions of RQ and RHH to determine the relationships between the attributes evaluated by each of the four indices and reference/non-reference conditions. We also looked into the relationships between RQ and RHH as well as between these indices and the local macroinvertebrate communities. We surveyed riparian vegetation and river habitat characteristics in a total of 285 river reaches, each 500 m in length, along the fluvial network of Cantabria. These data were combined with previous macroinvertebrate community records from a total of 52 river reaches, and the Index of Average Score per Taxon (IASPT) metric was calculated for comparison. Reference condition sites were selected in 10 river types for the purpose of the present study on the basis of (1) unaltered discharge, (2) non-intensive land uses and (3) no or minimal morphological changes. There were 96 river reaches that matched the reference conditions. QBR and RQI were sensitive to both reference and nonreference conditions in the official river types and were larger in reference conditions than in non-reference conditions for most of the river types. However, IHF and HQA could only differentiate some of the river types and could not distinguish between reference and non-reference conditions. Moreover, IHF and HQA did not have a similar response to human modifications across river types, as reference reaches presented larger or lower values than non-reference conditions depending on the river type. Finally, RQ was positively correlated to RHH, and IASPT increased with both. We concluded that RQI and HQA performed slightly better than QBR and IHF indices to distinguish between reference and non-reference sites in the rivers of Cantabria and that river habitat heterogeneity should not be used to assess river habitat quality

Influence of data sources and processing methods on theoretical river network quality

ABSTRACT: Stream ecosystem research and water resource management need to be considered over broad spatial scales. Moreover, the investigation of the spatial configuration and habitat characteristics of streams requires an accurate and precise spatial framework to reflect a catchment's physical reality that can successfully explain observed patterns at smaller scales. In this sense, geographic information systems represent an essential tool to satisfy the needs of researchers and managers. Specifically, theoretical river networks (TRNs) extracted from digital elevation models (DEMs) have become much more common in recent years, as they can provide a suitable spatial network and hierarchical organisation to sort out river ecosystem information from reach to catchment levels. Nevertheless, the quality of the extracted TRN depends greatly on the spatial resolution of the DEM and the methodology used in the network extraction processes. In this study, we compare the quality of 9 TRNs extracted from DEMs with different spatial resolutions ranging from regional (5 m) to national (25 m) and global scales (90 m) using the ArcHydro, Hec-GeoHMS and Netstream software packages. To achieve our goal, we compared (i) the DEM-derived slope; (ii) the spatial accuracy of the TRNs in relation to a control river network; (iii) the structure of the TRNs through analysis of the number of river segments, average river segment length and total river length by stream order, drainage density and the mean upstream slope throughout the TRN; and (iv) the ability of variables derived from TRNs to discriminate among stream types classified according to flow type and substrate composition. We demonstrated that not only DEM spatial resolution but also the DEM data source and raster creation process exert an important influence on terrain characteristics derived from DEMs and TRN properties. Moreover, TRNs extracted with NetStream generally showed better performance than those extracted with ArchHydro and HecGeoHMS. Nevertheless, river network extraction quality, DEM spatial resolution and extraction algorithms exhibit complex relationships due to the large number of interacting factors.The work described in this paper is part of a research project financed by the National Plan (2008-2011) for Research in Science & Technology of the Spanish Government (Project CTM2009-07447). The authors appreciate the valuable suggestions of anonymous reviewers that greatly improvement the document

Integrating monitoring, expert knowledge and habitat management within conservation organisations for the delivery of the water framework directive: A proposed approach

RESUMEN. Existe una creciente necesidad de entender mejor la naturaleza de las relaciones entre los atributos ambientales y las comunidades/especies de agua dulce para poder desarrollar acciones apropiadas que minimicen el impacto del cambio ambiental en los ecosistemas fluviales. Tal entendimiento necesitaría estar basado en investigaciones de relaciones causales más que en estudios de correlaciones estadísticas, como se acostumbra. Otro aspecto es la identificación de la escala a la cual los procesos y las características deben ser medidas para permitir un diseño de programas de monitoreo relevante. En este artículo se presenta una breve revisión de los conocimientos existentes sobre las relaciones especies/hábitat y se discuten los marcos teóricos existentes para la identificación de las características ambientales de importancia para la fauna y la determinación de la escala/s a la que deben evaluarse. Asimismo, proponemos un método para utilizar esas relaciones en el contexto de la supervisión y las prácticas de gestión en las organizaciones de conservación. Mostramos como modelos conceptuales de relaciones entre hábitats y especies pueden ser construidos usando el conocimiento existente y la opinión de expertos y como pueden ser testados utilizando datos recogidos como parte de los programas de monitoreo en las instituciones encargadas de la conservación. Sugerimos que tal marco, si aplicado, podría no sólo ayudar a identificar relaciones causales entre especies, características y procesos actuando a varias escalas, sino también para iniciar un proceso de adquisici´on de conocimiento en las instituciones responsables de la implementación de la Directiva Marco del Agua.ABSTRACT. There is a growing necessity to better understand the nature of the relationships between environmental attributes and freshwater species/communities to enable meaningful action to take place against the impacts of environmental change in river ecosystems. Such understanding would need to be based on the investigations of causal relationships rather than the study of statistical correlations or the use of expert opinion as is generally the case. Another issue is in identifying the scale(s) at which process and features should be recorded and assessed to enable the design of relevant monitoring programs. In this paper, we present a short review of existing knowledge on species/habitat relationships and discuss the importance of adequate theoretical frameworks for identifying environmental features of importance to wildlife and determining the scale/s at which they should be assessed.We further propose an approach for eliciting those relationships within the context of monitoring and management practice in conservation organisations. We show how conceptual models of habitat-species relationships can be built using existing knowledge and expert opinion and tested on data collected as part of existing monitoring programs. We suggest such framework, if applied, could not only help identify causal relationships between species, features and processes acting at various scales, but also initiate a knowledge acquisition process within organisations responsible for the delivery of the Water Framework Directive

Effects of landscape metrics and land-use variables on macroinvertebrate communities and habitat characteristics

ABSTRACT: The growing number of studies establishing links between stream biota, environmental factors and river classification has contributed to a better understanding of fluvial ecosystem function. Environmental factors influencing river systems are distributed over hierarchically organised spatial scales. We used a nested hierarchical sampling design across four catchments to assess how benthic macroinvertebrate community composition and lower spatial scale habitat descriptors were shaped by landscape and land-use patterns. We found that benthic macroinvertebrate community structure and composition varied significantly from catchment to habitat level. We assessed and identified fractal metrics of landscape descriptors capable of explaining compositional and functional change in the benthic faunal indicators and compared them with the traditional variables describing land use and reach level habitat descriptors within a 1 km radius of each sampling site. We found that fractal landscape metrics were the best predictor variables for benthic macroinvertebrate community composition, function, instream habitat and river corridor characteristics