Lotic Biota Research Articles

The Impact of Catastrophic Floods on Macroinvertebrate Communities in Low-Order Streams: A Study from the Apennines (Northwest Italy)

Floods are normal components of many river regimes and, as such, they exert a significant influence at the ecosystem level. In recent decades, however, climate change has increased the frequency and intensity of floods, with serious consequences for lotic biota, particularly benthic macroinvertebrates, due to their limited mobility and sensitivity to disturbance. The impact of floods varies according to different biological parameters including the characteristics of the macrobenthic communities (taxonomic composition, morphology, behaviour, and life history traits) on one hand and various nonbiological parameters such as flood intensity, artificialisation of the river bed, the presence of dams, and many other factors on the other. Understanding these dynamics is pivotal to improve the effective management and conservation of aquatic ecosystems in the context of current climate change. The aim of this short communication is to evaluate the impact of a catastrophic flood on the macroinvertebrate community of a low-order Appennine stream (NW Italy). This will provide data regarding the varying impacts on different taxa and the recovery pattern of this significant component of the ecosystem.

Six decades of research on river temperature in Canada

River temperature is a key water quality variable in rivers and streams, as it modulates many other water quality variables as well as the metabolism, dispersion, and behavior of lotic biota. This paper reviews the key research milestones related to river temperature in Canada. The text focuses mostly on how research has been centrally motivated by the need to better understand and mitigate anthropogenic impacts on the thermal regime of rivers. The need for enhanced water temperature monitoring, both in situ and via remote sensing, especially in the Canadian North, is highlighted.

Restoring the ecological integrity of a dryland river: Why low flows in the Barwon–Darling River must flow

SummaryFor dryland rivers globally, understanding hydro‐ecological function is fundamental to informing trade‐offs between consumptive water use and aquatic ecosystem integrity. The Barwon–Darling is an Australian dryland river system recognised for its hydrological variability, which is considered a primary driver of the riverine ecosystem. Emphasis has been placed on extremes of zero flow and flood but examining low flow hydrology and hydraulics – through historical and modern droughts – demonstrates that under natural conditions, the river system also exhibits persistent and predictable flow characteristics. From 1885 to 1950, prior to flow regulation, the Barwon–Darling flowed 92% of the time, and throughout severe droughts (1895–1903 and 1939–1945) the river system was characterised by: near‐perennial flows (85% of the time), with lotic (flowing water) habitats; and near‐annual, in channel, flow pulses. Furthermore, evidence of lotic biota is found consistently in Aboriginal middens dating over the past 15,000 years, thus indicating the long‐term persistence of lotic conditions. We propose these consistent hydrological and hydrodynamic features have shaped the ecology of aquatic biota in the Barwon–Darling River but are now experiencing unprecedented change. Flow storage and diversion have increased the frequency and duration of zero flows in some reaches, but arguably the most substantial impacts, along the entire river, are on: (i) low flows, which are now frequently below lotic thresholds, and (ii) the magnitude of near‐annual flow pulses, which are reduced by over 90%. Consequently, in modern droughts, the river becomes predominantly lentic (still‐water), an impact that is exacerbated by weirpools which create artificial lentic conditions for approximately 1000 km (40%) of river. The ecological impacts of these changes are increasingly apparent, with the loss of lotic biota and a reduction in biodiversity. An ecohydraulic perspective explains present impacts, provides new directions and some immediate solutions for river management, and clarifies choices for stakeholders.

History, hydrology and hydraulics: Rethinking the ecological management of large rivers

AbstractClimatic extremes capture imaginations and provide a fundamental premise for biologists—that ecosystems are adapted to natural variability. Hence, understanding past extremes provides a template for contemporary ecological models and management. Nevertheless, myths can develop around historical climatic events, distorting perceptions of the past. The mythology of the Murray River in Australia is that over 100 years ago, it naturally “dried to a series of pools” in drought; therefore, the biota are flexible and adapted to hydrological variability and lentic habitats.Analysis of historical and modelled hydrology and hydrodynamics, however, demonstrates that: (a) cease‐to‐flow events were not natural and were instead caused by multiple small‐scale irrigation diversions; and (b) the Murray River had widespread perennial lotic habitats. Within a generation, the spatial, temporal, and causal context was lost and with it, the links between preregulation hydrology and hydraulics, and river ecology.From an intermittently lentic system, we propose an alternative model which integrates ecohydrology and ecohydraulics. Specifically, the model incorporates: (a) persistence of lotic in‐channel and lentic off‐channel refugia, even in droughts; and (b) a reliable spring flow pulse that increases hydrodynamic complexity, promotes longitudinal integrity of lotic conditions and replenishes low‐lying wetlands. The model helps explain the decline of lotic biota, suggesting that hydraulic change has had a greater impact on aquatic biodiversity than changes in hydrology.Being mindful of historical conditions and considering spatio‐temporal ecohydraulics provides new opportunities for the rehabilitation of highly modified rivers and may assist the strategic development of large rivers, including for hydropower.

Tributary effects in rivers: interactions of spatial scale, network structure, and landscape characteristics

Landscape characteristics in combination with the physical structure of branched stream networks define the environmental conditions available for lotic biota. From simple stream network “laws” can emerge a spatially explicit understanding of habitat heterogeneity. Based on geographic information system analyses, we explore how stream networks integrate spatial heterogeneity of the landscape and form new characteristics as stream segments accumulate into progressively larger drainages and how these changes in landscape characteristics relate to confluence symmetry ratio and drainage size. Simple expectations for stream networks include the following: (i) abrupt changes in longitudinal patterns are more probable among the numerous small and diverse headwater streams than in large, rare, and characteristically similar tributaries, (ii) the many small tributaries flowing into large mainstem channels cause individually small, yet collectively gradual, changes in longitudinal patterns. Such a spatial understanding of where change is likely to occur helps to reconcile gradual river continuum and abrupt discontinuum views of patterns in rivers and predict the locations of important confluences, ecological transitions, longitudinal gradients, and patterns of biodiversity in stream networks.

Prediction of River Water Temperature and its Dependence on Hydro-Meteorological Factors

Rivers will be among the most sensitive of all ecosystems to the effects of climate change as they are heated by processes similar to those warming the Earth's atmosphere. The river water and air temperatures follow each other closely. The life cycle of lotic biota is regulated by two major physical factors: water temperature and hydraulic conditions. Any change in hydraulic pattern that leads to an alteration of the established thermal regime of a lotic ecosystem will ultimately lead to a dramatic change in the composition and survival of lotic biota. In order to assess the impacts of potential climate change on thermal regime of water bodies, it is important to know the long range forecasts for various climatic parameters. For this purpose the modelling of water discharge and forecasting of future changes are performed. This paper provides the long-term changes in the Lithuanian river water temperature according to two models and emissions scenarios. This paper evaluates the changes of warm season (May-October) water temperature and heat runoff of Lithuanian rivers (Nemunas, Merkys and Dubysa) with different thermal regimes at the end of the 21st century (2071–2100) comparing to the climate normal period (1961-1990) using two climate change models (ECHAM5 and HadCM3 global climate models and the A2 and B1 emissions scenarios) and hydrological modelling (HBV model). DOI: http://dx.doi.org/10.5755/j01.erem.68.2.6178

Restoring riffle-pool structure in an incised, straightened urban stream channel using an ecohydraulic modeling approach

Streams in urban and urbanizing watersheds are impacted by altered runoff hydrology and sediment yields, floodplain modifications, and channel relocations. One morphological response to urbanization is degradation of riffle-pool sequences. Pools and riffles are fundamental mesohabitat units where many lotic biota have evolved to occupy preferentially, and support diverse biological communities. Restoring self-maintaining pool-riffle structures is essential to the ecological rehabilitation of urban streams when lost. However restoring these structures can be problematic in straightened urban streams constrained by civil infrastructure preventing channel re-meandering. The project goal was to utilize geomorphic, hydraulic, and ecological principles to rehabilitate a study reach in a confined geomorphic setting with a primary emphasis on developing a stable riffle design that improves habitat patch dynamics. A 270-m tree-lined study site was selected on Beaver Creek, Knox County, East Tennessee. Through experimental 3D and 2D hydraulic modeling, a riffle-pool design was developed consisting of removing trees at expanded channel locations, placing 3.8-cm gravel substrate for the riffle bed, and deepening the pool prior to riffle entrance. Riffle-pool maintenance processes of the proposed design included occurrence of shear stress reversal between low- and high-flows, and high-flow acceleration-deceleration from pools to riffles. Cobble was interspersed on riffle surfaces for leaf pack formation. Root wads were positioned at bank locations potentially vulnerable to erosion. River2D provided useful design information to assess pre-construction channel stability and habitat quality. In this case study, an ecohydraulic modeling approach to urban stream restoration is described. Construction of four riffle-pool structures was completed in March 2012, and a geomorphic survey completed in April 2013 observed the riffle structures remained stable even with the project site experiencing eight bankfull events. Post-construction monitoring has shown that the unique design for planform-constrained urban channels has promise for increasing hydraulic habitat diversity and improving biotic integrity in these stressed environments.

The relationship between land-use, hydromorphology and river biota at different spatial and temporal scales: a synthesis of seven case studies

The aim of this paper is to summarize seven case studies that were analysed as part of research theme the interaction between land-use and climate forming part of EU-funded Euro-limpacs project Evaluating impacts of global change on European freshwater ecosystems. Different aspects of relationships between climate change, land-use at different spatial scales, in-stream hydrology and morphology, and lotic biota were studied. The papers included analyses of: i) effects of historical changes in stream hydromorphology and biota, ii) influences at different spatial scales on physical features (hydrology and morphology), and iii) influences at different spatial scales on lotic biota. A multitude of environmental variables and gradients at different spatial scales affect in-stream physical as well as biological parameters. Disentangling which of these variables extort strongest influence on hydromorphology and lotic biota seems to differ among studies as can be seen from seven papers summarized here. The studies showed a general pattern with gradients from up-stream headwaters to down-stream stream reaches with predictable changes in vegetation and hydromorphological relationships along gradient. This is of course nothing new, but rather it was surprising how many different spatial scales and types of environmental variables were found to be important in structuring in-stream physical and biotic variables in different studies. Further investigations using standardised sets of environmental variables and possibly also standardised biotic sampling methods as well as clear definitions of which spatial scales are investigated are needed to further disentangle importance of land-use at different spatial scales on in-stream hydromorphology and biota. It is also clearly necessary to widen analysis methods from correlative to such methods that investigate mechanistic relationships among variables within a catchment.

Linking scales of flow variability to lotic ecosystem structure and function

AbstractObtaining a better knowledge of how flow variability affects lotic biota is of considerable importance to stream and river management. We contend that processes at different hierarchical levels of organization in lotic ecosystems are sensitive to variation in flow at related hierarchical temporal scales. Ecosystem disturbance caused by large‐scale events (i.e. infrequent, but high magnitude flow events with a recurrence interval of years to many days) tend to determine high‐level characteristics of ecosystem structure (e.g. determining species pools, periphyton versus macrophyte dominance) and function (e.g. balance between auto‐ and heterotrophy). The high‐level ecosystem characteristics then set the stage for processes that are influenced by flow variation that occurs at smaller temporal scale (i.e. minutes to milliseconds) such as colonization, biotic interactions and mass transfer enhancement of production. We contend that large‐scale temporal events predominantly affect lotic ecosystems through physical drag processes (‘drag‐disturbance’), whereas small‐scale flow variations affect ecosystems through mass‐transfer processes (including invertebrate and fish food‐uptake). Drag‐disturbance and mass‐transfer related processes mark the opposite ends of a continuum of flow variability controlled processes, with moderate temporal scale flow variability events affecting ecosystems through both drag‐disturbance and mass‐transfer processes in similar proportions. Flow variability, and associated effects on ecosystems, across these scales is discussed with reference to New Zealand rivers. We suggest that these concepts can be integrated across the full range of temporal scales based on a spectrum of velocity variations. This may provide a unifying conceptual model for how the structure and functioning of lotic ecosystems are linked to flow variability. Copyright © 2005 John Wiley & Sons, Ltd.

Macroinvertebrate instream flow studies after 20 years: a role in stream management and restoration

AbstractOver the past two decades of refinement and application of instream flow evaluations, we have examined the hydraulic habitat of aquatic macroinvertebrates in a variety of conditions, along with the role of these macroinvertebrates in sustaining ecosystem integrity. Instream flow analyses assume that predictable changes in channel flow characteristics can, in turn, be used to predict the change in the density or distribution of lotic species or, more appropriately, the availability of useable habitat for those species. Five major hydraulic conditions most affect the distribution and ecological success of lotic biota: suspended load, bedload movement, and water column effects, such as turbulence, velocity profile, and substratum interactions (near‐bed hydraulics). The interactions of these hydraulic conditions upon the morphology and behavior of the individual organisms govern the distribution of aquatic biota. Historically, management decisions employing the Physical Habitat Simulation (PHABSIM) have focused upon prediction of available habitat for life stages of target fish species. Regulatory agencies have rarely included evaluation of benthos for flow reservations. Although ‘taxonomic discomfort’ may be cited for the reluctant use or creation of benthic criteria, we suggest that a basic misunderstanding of the links between benthic macroinvertebrate and the fish communities is still a problem. This is derived from the lack of a perceived ‘value’ that can be assigned to macroinvertebrate species. With the exception of endangered mussel species (for which PHABSIM analysis is probably inappropriate), this is understandable. However, it appears that there is a greater ability to predict macroinvertebrate distribution (that is, a response to the change in habitat quality or location) and diversity without complex population models. Also, habitat suitability criteria for water quality indicator taxa (Ephemeroptera, Plecoptera, and Trichoptera; the so‐called ‘EPTs’) may also provide additional management options to stream regulators. The greatest application for macroinvertebrate criteria will be in low‐order streams where a more immediate link to fish communities can be established. We present an example from Queens Creek, in North Carolina, USA, in which monthly allocations required to preserve the integrity of the benthic macroinvertebrate community were significantly higher than for the target benthic fish species, Cottus bairdi. In the months when both Cottus and community diversity of macroinvertebrates were the ‘bottleneck’ life stages, preservation of only fish species could result in an additional 5–25% loss in macroinvertebrate habitat. We suggest that, as there becomes an increased emphasis on maintaining macroinvertebrates as monitors of stream health, there will be a concurrent emphasis on incorporating hydraulic habitat conditions as a part of bioassessment. Copyright © 2001 John Wiley & Sons, Ltd.

The effects of simulated irrigation induced changes in salinity on metabolism of lotic biota

A series of manipulative field experiments were conducted in the Elbow River, Alberta, Canada, using a modified metabolic chamber to determine the net primary productivity of epilithic algae and community respiration and the drift of macroinvertebrates exposed to pulses of four simulated salinities (1.2, 2.4, 4.5 and 8.2 ppt). Treatment salinities represented ionic composition and ratios of irrigation effluent emptying into the South Saskatchewan River system in southern Alberta compared to ambient concentrations in the river (0.4 ppt). Net primary productivity of benthic algae and oxygen consumption of macroinvertebrates increased with increasing salinity from 1.2 to 4.5 ppt but declined in the highest salinity. A significant time dependent and time and salinity dependent (combined) variability in benthic drift occurred. However, effects of interaction and salinity were insignificant when exposed to pulses of different salinities. The drift biomasses in control chambers were always significantly greater than that of the treatment chambers except in the highest salinity.

Biotic and Abiotic Controls in River and Stream Communities

Lotic ecologists share a major goal of explaining the distribution and abundance of biota in the world's rivers and streams, and of predicting how this biota will respond to change in fluvial ecosystems. We discuss five areas of research that would contribute to our pursuit of this goal. For mechanistic understanding of lotic community dynamics, we need more information on: 1. Physical conditions impinging on lotic biota, measured on temporal and spatial scales relevant to the organisms. 2. Responses of lotic biota to discharge fluctuations, including the processes that mediate community recovery following resets caused by spates or droughts. 3. Movements of lotic organisms that mediate gene flow, resource tracking, and multilevel species interactions. 4. Life history patterns, with special emphasis on ontogenetic bottlenecks that determine the vulnerability of populations confronting environmental perturbation. 5. Consequences of species interactions for community- and ecosystem-level processes in rivers and streams. Without attempting to be comprehensive in our review, we discuss limits and limitations of our knowledge in these areas. We also suggest types of data and technological development that would advance our understanding. While we appreciate the value and need for empirical and comparative information, we advocate search for key mechanisms underlying community interactions as the crucial step toward developing general predictions of responses to environmental change. These mechanisms are likely to be complex, and elucidation of interacting bilateral, or multilateral, biotic and abiotic controls will progress only with the continuing synthesis of community- and ecosystem-level approaches in lotic ecology.