The Ecological Importance of Unregulated Tributaries to Macroinvertebrate Diversity and Community Composition in a Regulated River

In regulated rivers, dams alter longitudinal gradients in flow regimes, geomorphology, water quality and temperature with associated impacts on aquatic biota. Unregulated tributaries can increase biodiversity in regulated environments by contributing colonists to the main channel and creating transitional habitats at a stream junction. We assessed whether unregulated tributaries influence macroinvertebrate communities in two mainstem rivers during summer low-flows. Three tributary junctions of upland cobble-gravel bed streams were surveyed in an unregulated and a regulated river in the Sierra Nevada Mountains, California, USA. We found distinct physical habitat conditions and increased macroinvertebrate abundance and diversity in unregulated tributaries on the regulated river, but macroinvertebrate diversity did not increase downstream of tributary junctions as predicted. On the unregulated river, macroinvertebrate diversity was similar in upstream, downstream and unregulated tributary sites. Our findings highlight that unregulated tributaries support high macroinvertebrate diversity and heterogeneous communities compared to the mainstem sites in a regulated river, and thus likely support ecological processes, such as spillover predation, breeding and refugia use for mobile taxa. We suggest unregulated tributaries are an integral component of river networks, serving as valuable links in the landscape for enhancing biodiversity, and should be protected in conservation and management plans

Bankfull discharge and recurrence intervals in Irish rivers

Different definitions of the bankfull condition in rivers are based on morphological characteristics, boundary conditions and geometrical properties. Consequently, the magnitude and associated return period of the bankfull discharge can be ambiguous. Knowledge of this discharge is important in index flood estimation and subsequent regional flood frequency analysis. This study investigates bankfull discharges and recurrence intervals at 88 locations in the Irish river network using a combination of surveyed bankfull levels, rating curves and equations and photographic records at the sites in question. Catchments ranged in area from approximately 23 km2 to 2778 km2. Recurrence intervals were determined by fitting generalised extreme value (GEV) distributions to the annual maximum flow series at the sites investigated. These intervals were found to be less than 2 years (the median annual flood) at 42 stations (48%) and less than 2·33 years (the mean annual flood assuming a GEV type 1 distribution) at 47 stations (53%). Higher return periods of between 2·33 and 10 years and 10 and 25 years were observed at a further 20% and 6% of locations respectively. Using multivariate regression analysis, the computed bankfull discharges are correlated with catchment descriptors and three expressions are presented for estimating bankfull flows.Deposited by bulk importPermission granted to archive the final PDF (the version used for publication that subscribers gain access to) but this not available yet. On the webpage that the file is hosted on, please reference the journal homepage (www.geotechnicaljournal.com) and including the text “Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.”TS 01.03.1

Parent-Adolescent Relationship Quality as a Moderator for the Influences of Parents’ Religiousness on Adolescents’ Religiousness and Adjustment

Prior investigations have demonstrated that parents’ religiousness is related inversely to adolescent maladjustment. However, research remains unclear about whether the link between parents’ religiousness and adolescent adjustment outcomes—either directly or indirectly via adolescents’ own religiousness—varies depending on relationship context (e.g., parent-adolescent attachment). This study examined the moderating roles of parent-adolescent attachment on the apparent effects of the intergenerational transmission of religiousness on adolescent internalizing and externalizing symptoms using data from 322 adolescents (mean age = 12.63 years, 45% girls, and 84% White) and their parents. Structural equation models indicated significant indirect effects suggesting that parents’ organizational religiousness was positively to boys’ organizational religiousness—the latter of which appeared to mediate the negative association of parents’ organizational religiousness with boys’ internalizing symptoms. Significant interaction effects suggested also that, for both boys and girls, parents’ personal religiousness was associated positively with adolescent internalizing symptoms for parent-adolescent dyads with low attachment, whereas parents’ personal religiousness was not associated with adolescent internalizing symptoms for parent-adolescent dyads with high attachment. The findings help to identify the family dynamics by which the interaction of parents’ religiousness and adolescents’ religiousness might differentially influence adolescent adjustment

Fish assemblage recovery along a riverine disturbance gradient

Artificial fluctuations in streamflow have been documented to alter the composition andstructure of stream communities. This study tests the hypothesis that a spatial recovery gradientin fish assemblage structure exists downstream of a hydroelectric dam, and that recovery can be identified by the presence and abundance of species largely restricted to flowing-water habitats(fluvial specialists). A longitudinal gradient of change in a shoreline fish assemblage wasquantified in a 66-km reach of a mid-sized, species-rich river (Tallapoosa River, Alabama) withdaily flow fluctuations from hydropower generation. The shoreline fish assemblage in a nearbyand similar river (Cahaba River, Alabama) was quantified as a regional reference for theoccurrence of fish assemblage gradients. Fish were collected with prepositioned areaelectrofishers in 240 randomly located sampling sites, and physical habitat was quantified. Usingdistributional and habitat use information, fish species were categorized as fluvial specialists ormacrohabitat generalists (species that occur in a wide variety of aquatic systems). Sampledhabitats were similar between rivers and along each study reach. The longitudinal pattern ofspecies occurrence and fish abundance was consistent in the free-flowing river. A longitudinalgradient of increasing abundance and richness of only fluvial specialist species existeddownstream of the hydroelectric dam. No similar spatial gradient existed for macrohabitatgeneralists in either river. Although a fish community recovery gradient was identified, a recoveryendpoint was not evident because assemblage change was gradual and possibly incomplete.The preservation and management of riverine fish faunas will partly depend on incorporatingspatial recovery into decisions about permitting and siting of anthropogenic changes like hydroelectric dams. http://dx.doi.org/10.2307/194192

Forecasting environmental responses to restoration of rivers used as log floatways : an interdisciplinary challenge

Log floating in the 19th to mid 20th centuries has profoundly changed the environmental conditions in many northern river systems of the world. Regulation of flow by dams, straightening and narrowing of channels by various piers and wing dams, and homogenization of bed structure are some of the major impacts. As a result, the conditions for many riverine organisms have been altered. Removing physical constructions and returning boulders to the channels can potentially restore conditions for these organisms. Here we describe the history of log driving, review its impact on physical and biological conditions and processes, and predict the responses to restoration. Reviewing the literature on comparable restoration efforts and building upon this knowledge, using boreal Swedish rivers as an example, we address the last point. We hypothesize that restoration measures will make rivers wider and more sinuous, and provide rougher bottoms, thus improving land-water interactions and increasing the retention capacity of water, sediment, organic matter and nutrients. The geomorphic and hydraulic/hydrologic alterations are supposed to favor production, diversity, migration and reproduction of riparian and aquatic organisms. The response rates are likely to vary according to the types of processes and organisms. Some habitat components, such as beds of very large boulders and bedrock outcrops, and availability of sediment and large woody debris are believed to be extremely difficult to restore. Monitoring and evaluation at several scales are needed to test our predictions