Tributaries, sediment sources, and the longitudinal organisation of macroinvertebrate fauna along river systems

2001 ◽  
Vol 58 (4) ◽  
pp. 824-840 ◽  
Author(s):  
S P Rice ◽  
M T Greenwood ◽  
C B Joyce
Keyword(s):  
Spatial Scales ◽  
River System ◽  
Water Volume ◽  
Physical Habitat ◽  
River Continuum ◽  
Regulated Rivers ◽  
New Model ◽  
Lotic Ecosystem ◽  
Continuum Concept ◽  
Stream Biota

Tributary confluences are sites along a main channel where, because of the introduction of water and (or) sediment, the water volume, bed sediment character, and water quality of the mainstream can change abruptly. These shifts ensure that abiotic gradients seldom vary smoothly or continuously for distances of more than 100–102 km along any river system. The ways in which tributaries and related sediment recruitment points structure longitudinal changes in physical habitat are examined. Variables of importance to stream biota are affected and, in turn, it is suggested that the arrangement of tributaries and related features is an important control on the longitudinal organisation of macroinvertebrate benthos at moderate spatial scales. A new model is presented that stresses the importance of hydrological and sedimentological networks for organising lotic fauna. The link discontinuity concept emphasises the discontinuous nature of lotic ecosystem gradients, addresses the importance of tributaries in unregulated as well as regulated rivers, and extends, to its logical conclusion, the limited recognition of tributary influence in the river continuum concept. A case study from British Columbia, Canada, illustrates the general merit of the new model.

Analysis of Longitudinal Zonation and the River Continuum Concept in the Oldman–South Saskatchewan River System

1982 ◽  
Vol 39 (9) ◽  
pp. 1258-1266 ◽  
Author(s):  
Joseph M. Culp ◽  
Ronald W. Davies
Keyword(s):  
River System ◽  
Subalpine Forest ◽  
Functional Feeding Groups ◽  
River Continuum Concept ◽  
Macroinvertebrate Communities ◽  
Terrestrial Vegetation ◽  
River Continuum ◽  
Longitudinal Zonation ◽  
South Saskatchewan River ◽  
Continuum Concept

During the summer–fall periods, the benthic macroinvertebrate communities of the Oldman–South Saskatchewan River system demonstrated a longitudinal zonation related to the subalpine forest, fescue prairie, and mixed prairie terrestrial ecosystems through which it flows. This zonation was primarily attributable to significant downstream increases in periphyton biomass, plant nutrients, and water temperature. Zonation was reduced in the Sate winter–spring periods and absent in May, during spring runoff. Longitudinal trends in macroinvertebrate functional feeding groups generally followed the predictions of the river continuum concept, with trophic composition apparently more strongly affected by autotrophic processes in the summer, and heterotrophic processes in the winter. By combining the river continuum concept with a watershed classification system based on geology, climate, soil type, and terrestrial vegetation, we suggest that biological comparisons of longitudinal zonation are enhanced.Key words: longitudinal zonation, reciprocal average ordination, river continuum concept, functional groups

scholarly journals Assessing the Rigidity of the River Continuum Concept to Fish Species in a Fluvially Dominated Southern African Coastal System

2021 ◽  
Author(s):  
Festus P. Nashima ◽  
Nadine A. Strydom ◽  
Stephen J. Lamberth
Keyword(s):  
Species Diversity ◽  
South African ◽  
Fish Assemblages ◽  
River System ◽  
River Continuum Concept ◽  
River Continuum ◽  
Coastal System ◽  
Estuarine Species ◽  
Continuum Concept ◽  
River Estuarine

Abstract A continuous gradient of physical and biological processes exists within a river system from headwaters to mouth, according to the River Continuum Concept. In this study, the River Continuum Concept was used to compare patterns in fish assemblages and diversity trends to Remane predictions. The findings show that species diversity is low near the estuary's mouth and increases upstream. While the presence of several marine and estuarine species increased species diversity upstream in the river due to the dominance of freshwater fishes, it decreased downstream due to the presence of several marine and estuarine species. These patterns are consistent with the biogeographical trend of decreasing species richness along the South African coast from east to west. Based on the findings of this study, the River Continuum Concept ignores plasticity, which is evident in species that use transitional waters. As a result, the concept is insufficiently valid for the Orange River Estuarine Continuum, and a new concept known as the “River-Estuarine Continuum” has been proposed.

Longitudinal trends in regulated rivers: a review and synthesis within the context of the serial discontinuity concept

2013 ◽  
Vol 21 (3) ◽  
pp. 136-148 ◽  
Author(s):  
Lucy Eunsun Ellis ◽  
Nicholas Edward Jones
Keyword(s):  
Environmental Flows ◽  
Benthic Invertebrate ◽  
Trophic Levels ◽  
Empirical Estimation ◽  
Resource Subsidies ◽  
River Continuum ◽  
Regulated Rivers ◽  
Continuum Concept ◽  
Serial Discontinuity Concept ◽  
Serial Discontinuity

Dams alter the geomorphology, water quality, temperature regime, and flow regime of lotic systems influencing the resources and habitat of fish, benthic invertebrates, and lower trophic levels. Since the inception of the river continuum concept and the serial discontinuity concept (SDC), biotic and abiotic impacts below impoundments have been the focus of many lotic studies. However, recovery gradients below dams are rarely examined in sufficient detail and no current synthesis of longitudinal impacts in regulated rivers exists. This understanding is needed to build ecological relationships in regulated rivers to inform environmental flows science and management. In this review, we provide evidence for SDC predictions on physical, chemical, and biological recovery in regulated rivers. Additionally, we determine how these changes are reflected in the benthic community. Our review suggests that two recovery gradients exist in regulated rivers: (1) a longer, thermal gradient taking up to hundreds of kilometres downstream; and (2) a shorter, resource subsidy gradient recovering within 1–4 km downstream of an impoundment. Total benthic invertebrate abundance varies considerably, with both increases and reductions observed at near-dam sites and varying in recovery downstream. Much of this variability stems from the degree of flow alteration and resource subsidies from the upstream reservoir. In contrast, benthic diversity is often reduced below dams irrespective of dam location and operation with little recovery observed downstream. The community at near-dam sites is largely composed of filter-feeding invertebrates which are quickly replaced downstream, while stoneflies are reduced below impoundments with limited downstream recovery. Despite a lack of formal testing, studies support SDC predictions. The SDC still provides a useful theoretical framework for hypothesis testing, and future studies should further expand the SDC to include empirical estimation within the context of the landscape.

Modeling freshwater mussel distribution in relation to biotic and abiotic habitat variables at multiple spatial scales

2014 ◽  
Vol 71 (10) ◽  
pp. 1483-1497 ◽  
Author(s):  
Ericka E. Hegeman ◽  
Scott W. Miller ◽  
Karen E. Mock
Keyword(s):  
Large Scale ◽  
Freshwater Mussels ◽  
Spatial Scales ◽  
Freshwater Mussel ◽  
Habitat Associations ◽  
Habitat Characteristics ◽  
Physical Habitat ◽  
Lotic Ecosystem ◽  
Unit Scale ◽  
Channel Unit

The habitat requirements of many native freshwater mussels remain unclear despite their imperiled status and ecological importance. To explore scale-specific habitat associations in the three genera of mussels found in the western United States (Anodonta, Gonidea, and Margaritifera) we used a multiscale random forest modeling approach to assess functional habitat parameters throughout a 55 km segment of the upper Middle Fork John Day River in northeastern Oregon. We characterized mussel occurrence and density with respect to the hierarchical, hydrogeomorphic structure by sampling reaches of varying valley confinement and channel units nested within individual reaches. Each genus exhibited unique longitudinal trends and channel unit-use patterns. In particular, the large-scale longitudinal trends in Margaritifera occurrence were associated with hydrogeomorphic characteristics at the reach and channel unit scale, with Margaritifera densities peaking in narrow valley segments and in riffles and runs. At the scale of the channel unit, all mussel genera responded to variation in physical habitat characteristics, particularly those that indicated more stable parts of the channel. Our results suggest that spatial patterns in freshwater mussels are associated with the hierarchical structuring of the lotic ecosystem and may provide guidance to restoration efforts.

scholarly journals Structure and integrity of fish assemblages in streams associated to conservation units in Central Brazil

2011 ◽  
Vol 9 (2) ◽  
pp. 445-454 ◽  
Author(s):  
Thiago Belisário d'Araújo Couto ◽  
Pedro De Podestà Uchôa de Aquino
Keyword(s):  
Fish Assemblage ◽  
Poecilia Reticulata ◽  
Fish Assemblages ◽  
Anthropogenic Activities ◽  
Water Volume ◽  
Physical Habitat ◽  
Wet Season ◽  
River Continuum ◽  
Conservation Units ◽  
Central Brazil

This study aims to characterize the spatial and seasonal distribution of the fish assemblage and evaluate the integrity of streams in a sustainable use area that includes integral protection conservation units in Distrito Federal, Central Brazil (Cerrado biome). For the study, 12 stretches of 8 streams were sampled in 2008 (dry season) and 2009 (wet season). For that evaluation was estimated the Physical Habitat Index (PHI), vegetation cover (VC), pH, dissolved oxygen, turbidity, and conductivity. We recorded 22 species, about eight undescribed species, by a total of 2,327 individuals. The most representative families in number of species were Characidae (31.8%), Loricariidae (31.8%), and Crenuchidae (13.6%). Knodus moenkhausii was the most abundant species with 1,476 individuals, added to Astyanax sp., Phalloceros harpagos, and Hasemania sp. they represent over 95% of the total abundance. The species Astyanax sp. (occurring in 79.2% of the stretches) and K. moenkhausii (50.0%) were considered constant in both seasons. The longitudinal gradient (River Continuum) exerts a strong influence on the studied assemblage. According to CCA, the variables that structure the fish assemblage are based on aspects related to water volume and habitat complexity. No seasonal variation in richness, diversity, abundance, and mass were detected. A cluster analysis suggests a separation of species composition between the stretches of higher and lower orders, which was not observed for seasonality. The streams were considered well preserved (mean PHI 82.9±7.5%), but in some stretches were observed anthropogenic influence, detected in the water quality and, mainly, on the riparian vegetation integrity. The exotic species Poecilia reticulata was sampled in the two stretches considered most affected by anthropogenic activities by PHI, conductivity, and VC.

scholarly journals ORCHILEAK (revision 3875): a new model branch to simulate carbon transfers along the terrestrial–aquatic continuum of the Amazon basin

2017 ◽  
Vol 10 (10) ◽  
pp. 3821-3859 ◽  
Author(s):  
Ronny Lauerwald ◽  
Pierre Regnier ◽  
Marta Camino-Serrano ◽  
Bertrand Guenet ◽  
Matthieu Guimberteau ◽  
...  
Keyword(s):  
Land Surface ◽  
Water Surface ◽  
Amazon Basin ◽  
River System ◽  
Terrestrial Ecosystems ◽  
Plant Litter ◽  
Mean Values ◽  
New Model ◽  
Canopy Soil ◽  
C Cycle

Abstract. Lateral transfer of carbon (C) from terrestrial ecosystems into the inland water network is an important component of the global C cycle, which sustains a large aquatic CO2 evasion flux fuelled by the decomposition of allochthonous C inputs. Globally, estimates of the total C exports through the terrestrial–aquatic interface range from 1.5 to 2.7 Pg C yr−1 (Cole et al., 2007; Battin et al., 2009; Tranvik et al., 2009), i.e. of the order of 2–5 % of the terrestrial NPP. Earth system models (ESMs) of the climate system ignore these lateral transfers of C, and thus likely overestimate the terrestrial C sink. In this study, we present the implementation of fluvial transport of dissolved organic carbon (DOC) and CO2 into ORCHIDEE (Organising Carbon and Hydrology in Dynamic Ecosystems), the land surface scheme of the Institut Pierre-Simon Laplace ESM. This new model branch, called ORCHILEAK, represents DOC production from canopy and soils, DOC and CO2 leaching from soils to streams, DOC decomposition, and CO2 evasion to the atmosphere during its lateral transport in rivers, as well as exchange with the soil carbon and litter stocks on floodplains and in swamps. We parameterized and validated ORCHILEAK for the Amazon basin, the world's largest river system with regard to discharge and one of the most productive ecosystems in the world. With ORCHILEAK, we are able to reproduce observed terrestrial and aquatic fluxes of DOC and CO2 in the Amazon basin, both in terms of mean values and seasonality. In addition, we are able to resolve the spatio-temporal variability in C fluxes along the canopy–soil–water continuum at high resolution (1°, daily) and to quantify the different terrestrial contributions to the aquatic C fluxes. We simulate that more than two-thirds of the Amazon's fluvial DOC export are contributed by the decomposition of submerged litter. Throughfall DOC fluxes from canopy to ground are about as high as the total DOC inputs to inland waters. The latter, however, are mainly sustained by litter decomposition. Decomposition of DOC and submerged plant litter contributes slightly more than half of the CO2 evasion from the water surface, while the remainder is contributed by soil respiration. Total CO2 evasion from the water surface equals about 5 % of the terrestrial NPP. Our results highlight that ORCHILEAK is well suited to simulate carbon transfers along the terrestrial–aquatic continuum of tropical forests. It also opens the perspective that provided parameterization, calibration and validation is performed for other biomes, the new model branch could improve the quantification of the global terrestrial C sink and help better constrain carbon cycle–climate feedbacks in future projections.

Strategies for Restoring River Ecosystems: Sources of Variability and Uncertainty in Natural and Managed Systems

2003 ◽  
Keyword(s):  
Spatial Variation ◽  
Spatial Scales ◽  
Spatial And Temporal Variability ◽  
Key Factors ◽  
Policy Makers ◽  
River Ecosystems ◽  
Spatial And Temporal Scales ◽  
Lower Productivity ◽  
Biological Attributes ◽  
Stream Biota

<em>Abstract</em>.—Productivity and biodiversity of stream and river ecosystems vary at multiple spatial and temporal scales. Spatial variation in productivity of salmonid fishes varies over two orders of magnitude worldwide and shows lesser, but still considerable, variation at the regional and watershed level. Spatial variation in production and diversity is related to variation in physical, chemical, and biological attributes of watersheds and channels. Channel constraint, gradient, and size are key factors in determining productivity and diversity. Constrained reaches generally support different species and lower productivity than lower-gradient, unconstrained channels. Variation in the condition of stream reaches is greatly influenced by disturbances. Severe disturbances fundamentally change the functional and structural properties of stream ecosystems and alter the way in which the surrounding watershed interacts with the stream. Periodic occurrence of disturbances and the process of recovery play a key role in maintaining spatial and temporal variability in stream conditions and thereby contribute to the productivity and diversity of stream biota. Land use by humans alters the frequency and characteristics of disturbances. As a result, human-altered disturbance patterns often homogenize channel conditions across a watershed rather than introducing diversity. Watershed restoration plans need to recognize the role variability and disturbance play in maintaining the productivity and diversity of stream biota. Incorporating this understanding into watershed management and restoration will require scientists, managers, and policy makers to view watersheds at much longer temporal and larger spatial scales than is currently done.

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