Stream regulation by small dams affects benthic macroinvertebrate communities: from structural changes to functional implications (original) (raw)
Related papers
2013
The macroinvertebrate communities of two mountain streams in the Sierra Cebollera Natural Park (La Rioja, Northern Spain) were studied to ascertain the changes in these communities and their ecological status, considering the two main pressures that exist in the area, i.e., the Pajares Reservoir and various wastewater discharges. While the alterations in the macroinvertebrate communities were minimal downstream of the wastewater discharges, significant changes were detected in the composition of the community in the stream reaches located downstream of the Pajares Reservoir. This major disturbance downstream of the dam was especially intense in those reaches affected by a massive growth of the invasive algae Didymosphenia geminata, which might be related to dam operation. Despite a small decrease in the different biotic indices used, especially IBMWP and IMMi-T, downstream of the Pajares Reservoir, no large changes in the biological quality levels were detected (from high to good conditions). We conclude that the biotic indices did not completely reflect the changes produced by the disturbances present in the studied streams, especially the effects produced by the presence of a large dam. This study highlights the importance of considering measures other than the biotic indices to study the ecological status of headwater streams and rivers using macroinvertebrates, such as multivariate analysis, when the main disturbance is the alteration of the physical habitat rather than organic pollution.
Contrasting impact of small dams on the macroinvertebrates of two Iberian mountain rivers
1998
The effects of two small dams of similar size located in different (second order) streams on the Rivers Poio and Balsemão, were studied during one year to assess the impact on the benthic community. In the first stream, regulation is for hydro-power generation purposes and, in the second one, the dam is used to divert water to a small town. These distinct purposes affect the natural hydrological regime differently and the objective was to detect precisely how this reflects on the structure of the benthic communities. Composition of the benthic fauna was compared using multivariate techniques, both below and above the reservoir as well as in this habitat. Variation of diversity along the same reaches was also used to compare the impact on the biota. The results showed that the composition of the invertebrate fauna was only clearly modified downstream of the impoundment on the Balsemão. Here, the longer retention of the water in the artificial lake led to a greater accumulation of allochthonous organic matter, with consequences on the availability of this material below the reservoir, thus modifying the trophic structure. Decrease of diversity was, however, more pronounced in the Poio, reflecting the stress caused by the relatively frequent fluctuations in water flow.
Hydrobiologia, 1996
Relationships between the fish community and selected habitat features were examined in a set of short temperate streams located at the northern end of the Iberian Peninsula. The fish fauna in these streams consists mostly of diadromous or estuarine species. Species richness and diversity increased with stream order, depth and width and decreased with elevation and distance from the sea. Stream order (positively) and elevation (negatively) were the two variables most highly correlated with species richness and diversity ; higher order streams (order 3-4) showed greater values of species diversity than lower order ones (order 1) even when the elevation effect was removed. Addition of species in the downstream direction, but no replacement or loss was evidenced. We also compared the observed values of species diversity with those predicted from habitat features for a set of locations above unpassable dams. A great majority of the sites showed lower than predicted diversity values, which is an expected outcome for this mainly migratory fish fauna .
Species diversity and functional assessment of macroinvertebrate communities in Austrian rivers
Limnology, 2006
We applied an extensive data set from 211 locations along Austrian rivers to assess community structure and the ratios of functional feeding groups of benthic macroinvertebrates. A total of 569 taxa have been identified. At the catchment scale, the Enns, Salzach, and Traun Rivers exhibited the highest taxa richness whereas the Inn River showed the lowest richness. Beta-diversity was highest along the impounded and fragmented Enns and Drau Rivers. Consequently, high corridor diversity corresponded to a low degree of nestedness. Overall, scrapers and gathering-collectors dominated the benthic community. Further, the relationship between habitat conditions and metrics based on functional feeding groups were statistically analyzed to validate the potential of these metrics as indicators of ecosystem attributes. We examined four major ecosystem attributes: species diversity, material cycling, longitudinal material transport, and lateral material input. Multiple regression analyses for midorder rivers demonstrated that metrics were significantly related to habitat conditions. For example, the metric set indicating primary production was positively correlated with periphyton cover, dissolved oxygen, dominant sediment size, and average annual discharge. Overall, most metrics exhibited unique responses to habitat conditions, implying that they are useful proxies of ecosystem attributes. Thus, a functionbased approach based on macroinvertebrates has the potential to become an effective tool for the assessment of river ecosystems.
River Research and Applications, 2013
Dam removal to restore ecologically impaired rivers is becoming increasingly common. Although the target often is to facilitate fish migration, dam removal has also been assumed to benefit other types of organisms. Because few studies thus far deal with effects of dam removal on stream macroinvertebrates and because results have been equivocal, we investigated both short-and longer-term dam-removal effects on downstream macroinvertebrate communities. We did this in a before-and-after study of the removal of a dam located in a south Swedish stream. We sampled the benthic fauna 6 months before dam removal and both 6 months and 3.5 years after the dam was removed. We compared species composition, taxonomic richness, total densities and densities of macroinvertebrate groups before and after dam removal and between downstream and reference sites. We found that dam removal reduced some macroinvertebrate taxa at the downstream site, but we found no effect on community composition. Although this corroborates results from previous short-term studies, we also found a reduction of taxonomic richness and that some dam-removal effects persisted or even increased over time. The most likely explanation for the suppression of benthic macroinvertebrate richness following dam removal is a significantly increased sediment transport from the former reservoir and a subsequent loss of preferred substrates. Our results indicate that adverse dam-removal effects may be long lasting but taxon specific. We therefore call for longer-term studies on a variety of organisms to better understand how dam removal may influence downstream macroinvertebrate communities.
Ecological Indicators, 2010
While compositional diversity is a common metric for assessing human impacts on aquatic communities, functional diversity is scarcely employed, though highly desirable from the perspective of the European Water Framework Directive. Using abundance data from 99 minimally disturbed sites (i.e., no or very weak anthropogenic impact) from a national survey, we studied the spatial variability of compositional and functional biodiversity metrics across a predefined ecoregional classification. Metrics of compositional diversity comprised taxonomic and EPT richness and Simpson diversity. Functional diversity metrics were based on Rao's Quadratic Entropy (RQE), which described the differences among benthic invertebrate genera in eleven biological traits (e.g., size, life cycle, reproduction types, feeding habits). Using generalized linear models we show that taxonomic richness may vary greatly across ecoregions, contrasting with Simpson diversity and functional metrics that varied weakly in response to natural environmental variability. Functional diversity metrics, because of their stability in response to natural environmental variability, may be useful tools for assessing human impairment to ecosystem function. We further tested the response of functional diversity metrics to a specific human impact (sewage) and demonstrated significant modifications of functional diversity downstream of sewage pollution. Further investigations are required to test the ability of functional diversity metrics to precisely and accurately indicate different types of human impacts.
Water
The Guayas River basin is one of the most important water resources in Ecuador, but the expansion of human activities has led to a degraded water quality. The purpose of this study was (1) to explore the importance of physical-chemical variables in structuring the macroinvertebrate communities and (2) to determine if the thresholds in stream velocity related to macroinvertebrate community composition could be identified in the Guayas River basin. Thus, macroinvertebrates and physical–chemical water quality variables were sampled at 120 locations during the dry season of 2013 in the Guayas River basin. Canonical correspondence analysis (CCA) was performed to identify relevant physical–chemical characteristics of the river influencing the distribution of the macroinvertebrate communities. Threshold indicator taxa analysis (TITAN) was used to discriminate between the macroinvertebrate community related to stagnant waters (Daule–Peripa reservoir) and to running waters. CCA indicates tha...
Macroinvertebrate community structure in a regulated river segment with different flow conditions
River Research and Applications, 2002
Two types of modification of the hydrological system are present in the same regulated segment of the Lima River (NW Portugal): (a) a reduced and constant flow from hypolimnetic release; (b) an intense irregular flow (daily and seasonal). Using multivariate techniques it was possible to compare the effects of these two kinds of disturbance on the macroinvertebrate communities. The communities colonizing both sites exhibited a higher variation in composition and diversity when compared to undisturbed sites. However, such variability was even more evident in the first case, in spite of the stability of the environmental conditions. Such temporal replacement of species is linked to the dominance of tolerant taxa with short life cycles. In the regulated segment the poor water quality and the lack of litter input impacted mainly on the shredders group. This work shows the failure of the practice of releasing constant flows as an attempt to mitigate regulation impacts. Copyright © 2002 John Wiley & Sons, Ltd.
Hydraulic requirements of stream communities: a case study on invertebrates
Freshwater Biology, 2004
1. We relate invertebrate assemblages to direct measurements of near-bed hydraulic conditions that integrate the complex three-dimensional structure of flow close to the bottom. 2. We sampled invertebrate taxa from a Mediterranean River along a spatial gradient of increasing shear stress in two seasons (spring and autumn) with different hydrological conditions. We used a recently described ordination technique, Outlying Mean Index (OMI) analysis, to study the response of stream invertebrates to near-bed hydraulic parameters. 3. The distribution of nearly 70% of the taxa collected was significantly related to the hydraulic parameters assessed. In both seasons, shear stress and Froude number were the most important hydraulic parameters whereas substratum particle size and bed roughness had less influence. Most of the 31 taxa collected in both seasons had a higher OMI (an index showing the deviation between the mean environmental conditions used by a taxon and the mean environmental conditions used by a theoretical taxon uniformly distributed across the studied gradient) in autumn (when flow was greater) and were found in samples with high shear stress and high Froude number. This suggests that benthic invertebrates changed their preferences according to flow conditions. 4. Taxon richness declined with increased shear stress during lower flow in spring. Finally, and agreeing with previous results, the proportion of filter feeders and collector-gatherers was inversely related to shear stress. 5. Our results are a first step towards better habitat suitability models that could inform management decisions.