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 review of river habitat characterisation methods: indices vs. characterisation protocols

RESUMEN. Una gran variedad de metodologías se han propuesto para la caracterización de los hábitats fluviales a fin de cumplir con diferentes objetivos medioambientales. Esta diversidad de métodos puede ser vista como una ventaja para hacer frente a diferentes objetivos ambientales. Sin embargo, el seguimiento a medio o largo plazo de las características físicas del hábitat fluvial carece de una metodología estandarizada, lo cual contrasta con otros métodos mucho mejor establecidos para el seguimiento de otros componentes del ecosistema fluvial. Se han hecho algunos intentos para estandarizar los métodos de caracterización de los hábitats fluviales, y estos incluyen el estándar europeo para la evaluación de las características hidromorfológicas de los ríos (CEN, 2002), y el desarrollo del módulo de evaluación fisicoquímica dentro del sistema australiano de evaluación fluvial (AusRivAS). Uno de los primeros pasos para avanzar en el desarrollo y uso de métodos para la caracterización de los hábitats fluviales en los programas de seguimiento a medio y largo plazo es revisar las prácticas actuales a fin de poder abordar las deficiencias e introducir mejoras. En el presente trabajo se revisan más de 50 métodos que se han utilizado para caracterizar los hábitats fluviales en todo el mundo, utilizando el estándar europeo como referencia para comparar los métodos. Los métodos de caracterización de los hábitats fluviales se diferencian principalmente por tres razones: (1) los objetivos para los que fueron diseñados, (2) el tiempo que demanda su aplicación y (3) unos miden mientras otros evalúan las características del hábitat. Las características del cauce y de la zona ribereña son consideradas por un mayor número de métodos que las características de la llanura de inundación. Además, entre todas las características del hábitat fluvial descritas, la estabilidad de las orillas, el sustrato del lecho, las estructuras artificiales, la estructura de la vegetación ribereña, las dimensiones del cauce, el tipo de flujo o el caudal, los usos del suelo adyacentes y las barras de sedimentos son las más comúnmente registradas. Se concluye que los métodos de medición de las características del hábitat fluvial que recogen información cuantitativa cubriendo diferentes escalas espaciales podrían ser los más eficaces, ya que proporcionan bases de datos más amplias que permiten utilizar la información para diversos objetivos. Por último, algunos tipos de ríos, como los ríos intermitentes, requieren un mayor estudio para poder identificar correctamente los atributos físicos y la metodología adecuada para realizar el seguimiento de las características del hábitat.ABSTRACT. A wide variety of methodologies have been proposed for characterising river habitats in order to meet different environmental objectives. However, mid- to long-term monitoring of the physical characteristics of river habitats lacks a standardised methodology. This contrasts with well-established methods for monitoring other river ecosystem components. Some attempts have been made to standardise the methods for characterising river habitats including the European Guidance Standard for Assessing the Hydromorphological Characteristics of Rivers (CEN, 2002) and the Physical and Chemical AssessmentModule within the Australian River Assessment System (AusRivAS). One of the first steps toward advancing the development and use of methods for characterising river habitats in mid- to long-term monitoring programs is to review current practices so that deficiencies can be identified and addressed. In the present work, we review more than 50 methods that have been used to characterise river habitats worldwide. This review uses the European standard as a reference benchmark for comparison with existing methods of river habitat characterisation. Methods of characterising river habitats differ mainly with respect to three features: (1) the objectives for which they were designed, (2) the time required for their application and (3) whether they measure characteristics or evaluate them. Channel and riparian zone characteristics are more extensively covered than floodplain characteristics. Moreover, of all the described river habitat characteristics, bank stability, channel substrate, artificial structures, riparian vegetation structure, channel dimensions, flow types or flow status, adjacent land uses and bars are the most commonly recorded.We conclude that assessment methods of river habitat characteristics that gather quantitative information at a range of spatial scales could be the most effective, as they provide relatively extensive data sets that can be used to analyse information for several purposes. Finally, some types of rivers, such as intermittent rivers, require further work in order to identify their physical habitat characteristics and the proper monitoring methodology

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

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

The influence of methodological procedures on hydrological classification performance

ABSTRACT: Hydrological classification has emerged as a suitable procedure to disentangle the inherent hydrological complexity of river networks. This practice has contributed to determining key biophysical relations in fluvial ecosystems and the effects of flow modification. Thus, a plethora of classification approaches, which agreed in general concepts and methods but differed largely in specific procedures, have emerged in the last decades. However, few studies have compared the implication of applying contrasting approaches and specifications over the same hydrological data. In this work, using cluster analysis and modelling approaches, we classify the entire river network covering the northern third of the Iberian Peninsula. Specifically, we developed classifications of increasing level of detail, ranging from 2 to 20 class levels, either based on raw and normalized daily flow series and using two contrasting approaches to determine class membership: classify-then-predict (ClasF) and predict-thenclassify (PredF). Classifications were compared in terms of their statistical strength, the hydrological interpretation, the ability to reduce the bias associated with underrepresented parts of the hydrological space and their spatial correspondnece. The results highlighted that both the data processing and the classification strategy largely influenced the classification outcomes and properties, although differences among procedures were not always statistically significant. The normalization of flow data removed the influence of flow magnitude and generated more complex classifications in which a wider range of hydrologic characteristics were considered. The application of the PredF strategy produced, in most of the cases, classifications with higher discrimination ability and presented greater ability to deal with the presence of distinctive gauges in the data set than using the ClasF strategy.This study was partly funded by the Spanish Ministry of Economy and Competitiveness as part of the project MARCE (Ref: CTM-2009-07447; http://marce.ihcantabria.es/) and the Ministry of Agriculture, Food and Environment as part of the project RECORAM (ref: 132/2010). José Barquín is supported by a Ramon y Cajal grant (ref: RYC-2011-08313) of the Ministry of Economy and Competitiveness

Introducing a Mechanistic Model in Digital Soil Mapping to Predict Soil Organic Matter Stocks in the Cantabrian Region (Spain)

ABSTRACT: Digital soil mapping (DSM) is an effective mapping technique that supports the increased need for quantitative soil data. In DSM, soil properties are correlated with environmental characteristics using statistical models such as regression. However, many of these relationships are explicitly described in mechanistic simulation models. Therefore, the mechanistic relationships can, in theory, replace the statistical relationships in DSM. This study aims to develop a mechanistic model to predict soil organic matter (SOM) stocks in Natura2000 areas of the Cantabria region (Spain). The mechanistic model is established in four steps: (a) identify major processes that influence SOM stocks, (b) review existing models describing the major processes and the respective environmental data that they require, (c) establish a database with the required input data, and (d) calibrate the model with field observations. The SOM stocks map resulting from the mechanistic model had a mean error (ME) of -2 t SOM ha−1 and a root mean square error (RMSE) of 66t SOM ha-1. The Lin's concordance correlation coefficient was 0.47 and the amount of variance explained (AVE) was 0.21. The results of the mechanistic model were compared to the results of a statistical model. It turned out that the correlation coefficient between the two SOM stock maps was 0.8. This study illustrated that mechanistic soil models can be used for DSM, which brings new opportunities. Mechanistic models for DSM should be considered for mapping soil characteristics that are difficult to predict by statistical models, and for extrapolation purposes.This research was financially supported by the Environmental Hydraulics Institute ‘IH Cantabria of Universidad de Cantabria’ and the CGIAR Research Programme on Climate Change, Agriculture and Food Security (CCAFS). The CCAFS project is carried out with support from CGIAR Fund Donors and through bilateral funding agreements. Besides the financial support, we would like to thank Sara Alcalde Aparicio for collaboration in the collection and analyses of soil samples