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"River regulation"
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Ecosystem services provided by river-floodplain ecosystems
River-floodplain ecosystems (RFEs) provide multiple ecosystem services. However, their importance may be underestimated because they are not summarized yet. In this paper, we review and update the benefits that RFEs provide to society, including supporting, regulating, provisioning, and cultural ecosystem services. Although considered a unique ecosystem service category, we advocate that supporting services, like soil formation, nutrient cycling, primary production, and habitat provisioning can be comprehended as ecosystem processes that generate other services. RFEs provide valuable regulating services, including water regulation, storm protection, erosion control, water purification, waste treatment, and disease control. The society also benefits from provisioning services from RFEs, such as water for drinking and irrigation, food (e.g., fishes and crops), fiber, ornamental and biochemical resources, and energy production. RFEs also provide cultural services including recreation, ecotourism, religiosity, and spirituality. Most ecosystem services from pristine and human-altered RFEs are primarily regulated by the flood pulse because it maintains temporal and spatial habitat variability, high biodiversity, and biotic and abiotic interactions. Despite providing many benefits to society, RFEs are seriously threatened, mainly due to river regulation, land-use changes, pollution and invasive species. Consequently, the multiple demands and uses of RFEs worldwide raise challenges of conservation and restoration.
Journal Article
River systems under peaked stress
The change in the global energy production mix towards variable renewable energy sources requires efficient utilization of regulated rivers to optimise hydropower operations meet the needs of a changing energy market. However, the flexible operation of hydropower plants causes non-natural, sub-daily fluctuating flows in the receiving water bodies, often referred to as ‘hydropeaking’. Drastic changes in sub-daily flow regimes undermine attempts to improve river system health. Environmental decision makers, including permitting authorities and river basin managers facing the intense and increasing pressure on river environments, should consider ecosystem services and biodiversity issues more thoroughly. The need for research innovations in hydropeaking operation design to fulfil both the water and energy security responsibilities of hydropower is highlighted. Our paper outlines optimized hydropeaking design as a future research direction to help researchers, managers, and decision-makers prioritize actions that could enable better integration of river science and energy system planning. The goal of this is to find a balanced hydropower operation strategy.
Journal Article
Flow event size influences carbon, nutrient and zooplankton dynamics in a highly regulated lowland river
River regulation and water extraction has significantly altered flow regimes and reduced flood events in many inland river systems. Environmental flows have been adopted in many systems to mitigate the ecological impacts of river regulation, however a lack of knowledge regarding the interrelationship between flow regimes, carbon transport and instream productivity make prioritising water management difficult. To address this knowledge gap, we conducted a study on the Namoi River in the Murray-Darling Basin, Australia, monitoring changes in dissolved organic carbon (DOC), nutrient dynamics and planktonic food web structure during a period of variable flows. Nutrient and DOC concentrations were positively correlated with river discharge and zooplankton concentrations were highest post flow events. Planktonic chlorophyll-
a
, increased DOC concentration and higher discharge were the most influential drivers of change in zooplankton communities. Further, our results indicated that flow events increased production through both heterotrophic and autotrophic pathways, significantly boosting zooplankton concentration compared to base flow conditions across all measured flow events. We suggest even small in-channel flow events can be important for increasing basal and zooplankton production in rivers, and therefore should be protected or promoted by environmental flow management, particularly during drought conditions.
Journal Article
Propagule pressure and environmental filters related to non-native species success in river-floodplain ecosystems
The flood pulse is the main driving force influencing river floodplain ecosystems. The dominant role of the flood pulse on the success of non-native species (NNSs) is what differentiates floodplains from other ecosystems, in terms of invasion. In this review, I discuss some patterns related to the performance of NNSs in response to the flood pulse. First, floods connect floodplain habitats and spread propagules of NNSs, causing ‘propagule pulses’ in these ecosystems. After the establishment of NNSs, floodplains may function as steppingstones for future invasions, because propagule pulses enhance invasions in nearby landscapes. Second, the flood pulse changes environmental filters, with consequences for invasion success and for the coexistence of native and NNSs. Flooding represents a disturbance that enhances the success of some NNSs by reducing biotic resistance and changing resource availability, but diminishes the success of others. Drought enhances the invasion success mainly of NNSs that colonize the aquatic-terrestrial transition zone. Third, impacts caused by river regulation and global changes alter the flood pulse, which in turn affects invasion success. There is a great degree of idiosyncrasy in these patterns, but they pose a broad perspective that helps to understand and manage NNSs in floodplains.
Journal Article
Season and Flow Drive Productivity of a Regulated River
Flow regimes of river ecosystems worldwide have undergone substantial changes because of water resource development, altering the way in which organic matter is generated and cycled throughout entire river catchments. Flow–ecology studies have focused on structural variables measured at small spatial scales. This creates a challenging mismatch when applying adaptive flow management for ecosystem functioning at a catchment or regional scale. Here, we sought to inform flow management by evaluating the drivers of ecosystem metabolism in a regulated river and assessing our ability to predict metabolism at unmonitored locations. We estimated rates of ecosystem metabolism from high-frequency monitoring of dissolved oxygen concentration at eight sites on the Lachlan River of Australia’s Murray–Darling Basin. We then applied a spatio-temporal stream network model to predict metabolism at unmonitored locations using only remotely sensed and gauging station predictor variables. Gross primary productivity (GPP) was higher at sites with lower mean annual discharge, and strong seasonal patterns in rates of productivity tended to be disrupted by rising flows. Similarly, ecosystem respiration (ER) was higher at sites with lower mean annual discharge and lower annual flow variation, but increased slightly in response to higher daily flows. Predictions at validation sites were generally accurate, albeit with substantial site-to-site variation. Our results suggest that flow changes may have altered metabolic rates from conditions prior to water abstraction and dam construction. These findings will assist in managing flows for ecosystem function outcomes and support extrapolation from monitored sites to the broad scales required for evaluating catchment-scale outcomes of river management.
Journal Article
Riparian plant guilds become simpler and most likely fewer following flow regulation
1. River regulation affects riparian systems world-wide and conservation and restoration efforts are essential to retain biodiversity, and the functioning and services of riverine ecosystems. Effects of regulation on plant species richness have been widely addressed, but the filtering effect of regulation on guilds has received less attention. 2. We used a functional trait approach to identify adaptive plant strategies through regulation-tolerant traits and predict shifts of riparian vegetation communities in response to regulation. We analysed variation in functional diversity across gradients of hydrological alteration in northern Sweden in relation to modified timing and infrequent major floods, along with frequent short-term inundation. 3. Functional richness was similar in all study sites, but species richness declined with increasing intensity of regulation, and the species lost were largely functionally redundant (i.e. co-existing species that have similar contribution to an ecosystem function). Guilds of species intolerant to waterlogging were particularly unsuccessful in most regulated sites as they were affected by hydropower dams which replace major fluvial disturbances with frequent short inundation events. We predict that this guild will disappear, with likely consequences for the entire riverine ecosystem. 4. Synthesis and applications. We conclude that functional traits tolerant to waterlogging or submergence and lack of major fluvial disturbances were key to understanding our results. We suggest that the functional trait approach can be integrated with knowledge of other ecosystem components to provide an understanding of ecosystem function that can be used to guide fluvial ecosystem management.
Journal Article
Community reassembly after river regulation: rapid loss of fish diversity and the emergence of a new state
Hydroelectric expansion has affected the functioning of most tropical rivers in the world. However, community reassembly in Neotropical impoundments remains poorly understood, because long-term studies are incipient. In this context, we evaluated temporal changes in fish diversity before and after the construction of Peixe Angical Dam, Upper Tocantins River, Amazon Basin. Specifically, we investigated changes in taxonomic (richness, abundance and species composition) and functional diversity (trait richness and composition) over a period of a decade. Fish assemblages were sampled at five sites along the river, between 2004 and 2014 (before and after river regulation). As predicted, taxonomic and trait richness declined in the impoundment, and the composition shifted over the years, with increasing dissimilarity between sites. We also observed significant changes in species abundance and trait composition. However, changes were abrupt and a novel community state emerged after the fifth year of the impoundment. After this period, richness and abundance tended to stabilize at low levels, with different species/trait composition when compared to the pre-damming period. Our results indicate that major changes in community structure occurred during the first years of the impoundment, with relevant losses in taxonomic and functional diversity, along with a rapid change towards a new state.
Journal Article
Freshwater mussel glochidia infesting anadromous Gaspereau below a hydroelectric generating station: implications for mussel conservation
The Wolastoq | Saint John River (W|SJR) in New Brunswick, Canada, is regulated by hydroelectric dams with the largest and furthest downstream being the Mactaquac Generating Station (MQGS). River regulation can disrupt ecosystem connectivity by restricting access to upstream habitat for fishes and parasitic mussel larvae dependent on fishes for dispersal. Following installation of the MQGS, the number of Gaspereau (Alewife,
Alosa pseudoharengus
[Wilson, 1811]) and Blueback herring,
Alosa aestivalis
[Mitchill, 1814]) that spawn in that region of theW|SJR has increased dramatically. We assessed ectoparasitic freshwater mussel glochidia on Gaspereau captured at the MQGS and found 100% infested with an average of 43.2 glochidia per fish. Glochidia infested gill rakers, with increasing intensities from the first to fourth gill arch (
P
< 0.001). At least one million Gaspereau are passed above the MQGS annually, suggesting that millions of glochidia are simultaneously passed upstream each year with their hosts. We sequenced mitochondrial markers (
ND1
,
COI
) to ascertain mussel species and confirm both Alewife and Blueback herring as hosts for Alewife Floater (
Utterbackiana implicata
[Say, 1829]). This study provides critical baseline data on symbiotic interactions tightly interwoven in this river ecosystem and demonstrate that river regulation and fish passage considerations are more complex than most management plans account for currently.
Journal Article
Small area and low connectivity constrain the diversity of plant life strategies in temporary ponds
Aim (i) To determine whether area and connectivity of temporary ponds can predict plant species diversity, and the diversity and abundance of different plant life histories; (ii) To explore whether pond connectivity with the river prior to river regulation predicts better plant diversity patterns than current pond connectivity, suggestive of possible effects of connectivity loss. Location Eastern Carpathian Mountains, Romania, Europe. Methods We fitted linear and generalized linear models (LM and GLM) to examine whether pond area and current distance from the Olt River predict plant species richness, Shannon diversity and relative cover of different social behaviour types and overall plant species richness and Shannon diversity. Using historical maps, we measured pond distance from the river ca. 60 years before the Olt River was regulated, and we refitted the LM and GLM models using pond area and past distance from the river as independent variables. Results Total plant species richness increased with pond area, and it decreased with the distance from the river, but total plant Shannon diversity index was affected, positively, only by pond area. The strength of responses to pond area and connectivity of species richness, Shannon diversity and relative cover varied across the different social behaviour types. Past and current distances between ponds and riverbeds had similar effects on plant diversity, with some evidence for stronger effect of the present connectivity on specialist species Shannon diversity and a weaker effect on disturbance tolerants, generalists and competitors. Main Conclusions Pond area and connectivity with the landscape are important predictors of the diversity of plant life history strategies, and therefore, useful tools in pond conservation. Consistent species richness and Shannon diversity responses of wetland specialists to pond area and connectivity make this life history type well suited for monitoring pond condition.
Journal Article