Rui Manuel Vitor Cortes1,â. , Maria Teresa Ferreira2, Simone Varandas Oliveira1 &. Francisco Godinho2. 1Depart. Florestal, Universidade de Trás-os-Montes e ...
Hydrobiologia 389: 51–61, 1998. © 1998 Kluwer Academic Publishers. Printed in the Netherlands.
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Contrasting impact of small dams on the macroinvertebrates of two Iberian mountain rivers Rui Manuel Vitor Cortes1,∗ , Maria Teresa Ferreira2 , Simone Varandas Oliveira1 & Francisco Godinho2 1 Depart.
Florestal, Universidade de Tr´as-os-Montes e Alto Douro, Apart. 202, 5001 Vila Real Codex, Portugal Enga. Florestal, Instituto Superior de Agronomia, Tapada da Ajuda, 1399 Lisboa Codex, Portugal (∗ author for corespondence)
2 Depart.
Received 6 August 1997; in revised form 19 August 1998; accepted 27 October 1998
Key words: regulation, macroinvertebrates, impact, resilience, trophic structure Abstract 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. Introduction There is an increasing amount of information on the composition of invertebrate communities below huge regulatory schemes in different geographical regions, particularly with regard to the analysis of extreme fluctuations in discharge. However, reference data is much less available for smaller-scaled structures in these communities. This is particularly evident in the Iberian Peninsula where most studies have considered the impact of hydropower generation on large or medium sized rivers (e.g. Prat et al., 1988; Muñoz & Prat, 1989; Fontoura & De Paw, 1991; Ibañez et al., 1995), and the interaction produced by eutrophication on the ecological discontinuity caused by reservoirs (e.g. Puig et al., 1987 & Sabater et al. 1989, 1991; see also Garcia de Jalon et al., 1991 for a short review). In small, unpolluted head streams, flow regulation seems to be relatively moderate and presumably
not producing any obvious physical alteration of the habitat or of the chemical composition of the water as the low water depth in the reservoir does not induce any obvious stratification. In fact, Petts (1984), after an extensive review, concluded that hypolimnial releases cause the most drastic changes. The resistence to studying the effects of small structures is probably due to the fact that the relationship between cause-and-effect is less easy to interpret. This happens because the high adaptation capacity of benthic fauna to flow variability in the low order streams (Castella et al., 1996) handicaps researchers looking for clear responses by the biota. Previous works on poorly buffered and naturally flowing streams located within the region considered in the present study (northern Portugal), show that zoobenthos assemblages are intimately dependent on the natural typology of physical and chemical factors and on allochthonous inputs (Cortes, 1992; Cortes et
52 al., 1995). In fluvial systems, food sources are dependent on flow, a parameter that determines the major carbon pathway, according to the model described by Vannote et al. (1980). Therefore, a small barrier creating only short periods of water retention may impact significantly on downstream aquatic communities and provoke differing effects according to the characteristics of the hydrological changes involved. The purpose of this present study is to analyse changes in the macroinvertebrate communities resulting from the presence of small impoundments with different uses (i.e. hydro-power and water supply), each of which has given rise to specific flow regimes.
Material and methods Description of the sites The two regulatory structures on the selected rivers present distinct features concerning their use. The Poio river has short-term fluctuations in discharge associated with hydro-power peaks, whereas the Balsemão exhibits a steady reduction in summertime flow (though, without cessation of flow) caused by the continuous water demand from the small town of Lamego, which has approximately 10 000 inhabitants. The catchment area of the Poio above the dam is 29.9 km2 and the average altitude is 1095 m whereas for the Balsemão these values are, respectively, 54.8 km2 and 975 m. However, the morphometric characteristics of the same sectors of these drainage basins are quite dissimilar, as can be clearly seen in Figure 1: The Poio basin has a circular shape (Gravellius coef. _1.08; average bifurcation ratio _3.90), a fairly low drainage density (1.39 km/km2), but a higher mean stream slope (0.0559 m/m). The Balsemão basin is more extended (Gravellius coef. _1.53; average bifurcation ratio _4.93), corresponding to a less pronounced longitudinal stream profile (0.0346 m/m) and a much higher drainage density (2.67 km/km2), characterised by a finely divided network of streams of short length and steep gradient (the numbers presented are from personal calculations). The size of both regulatory structures is quite similar: 26.8 m length with a wall height of 3.97 m (R. Balsemão), and 24.3 m length, wall height 4.24 m high (Poio dam) – data from the E.I.A. study. Summary statistics for a range of chemical and physical parameters are presented in Table 1. Water sampling took place in the non regulated section
Table 1. Values of chemical parameters (average, and standard deviation) from the Poio and Balsemão rivers River Poio Parameters pH Dissolved O2 (mg l−1 ) Conductivity (µS cm−1 ) Alkalinity (mg HCO3 - l−1 ) Hardness (mg CaCO3 l−1 ) COD - (mg O2 l−1 ) NO3 − (mg l−1 ) NO2 − (mg l−1 ) Cl− (mg l−1 ) SO4 2− (mg l−1 ) P2 O5 (mg l−1 ) SiO2 (mg l−1 ) Ca (mg l−1 ) mg (mg l−1 ) Fe (mg l−1 ) Na (mg l−1 ) K (mg l−1 ) Dissolved Solids (mg l−1 )
x¯
s
5.70 0.71 10.32 0.81 19.50 14.82 6.08 2.04 3.96 1.28 1.62 1.49 0.27 0.32 0.013 0.027 0.003 2.09 3.07 0.58 0.80 0.004 0.45 0.427 0.05 0.39 2.33 0.14 0.88 0.02 11.83 0.65 0.88 0.31 11.83 7.36
River Balsemão x¯
s
6.16 0.57 9.28 1.21 30.67 13.40 10.47 3.19 10.05 4.01 2.18 1.54 1.67 1.09 0.014 0.014 5.85 4.87 3.13 2.20 0.007 0.012 6.32 2.80 2.32 0.87 1.03 0.55 0.06 0.04 5.23 2.10 1.07 0.45 39.33 18.98
and in the same periods for the invertebrate collections. These analyses show that the water of the two streams is poorly mineralized, with the Poio having more acidic waters and a lower content of organic and inorganic substances. The higher nutrient content in the Balsemão is most likely related to the presence of some small-scale farming in its catchment area. Nevertheless, little pollution was evident, given the low range of variation for all the parameters, reflecting a clear chemical stability in these streams, in spite of their pronounced hydrological differences. Three sampling stations were established on each stream in order to assess the impact of regulation: immediately above the regulated section (up), in the artificial lake (r) and about 100 m below the notch weirs (dw). Particle size of the streambeds differed noticeably between sites in both streams. In the Poio, there was a general dominance of larger particles, such as medium and small boulders (>250 mm), whereas in the Balsemão the area above the weir was dominated by cobble fraction (60–250 mm) mixed with fine and medium gravel (2–8 mm), giving way in the lower station to large cobbles and medium boulders (120–350 mm). The morphology of the river banks was stable, with no significant variations in erosion and deposi-
53
Figure 1. Location of the two small catchments of the Poio and Balsemão rivers in Northern Portugal. The figure shows also the distinct drainage characteristics of both basins in the area limited downstream by the dams (which are indicated by the symbol N).
54
Figure 2. Classification based on WPGMA of the dataset from both rivers Poio and Balsemão for all the sampling periods. The first letter represents the river, followed by the reach code (up – above, r – reservoir, dw – below the dam) and the month designation.
tion, due to reduced anthropogenic influences. There was dense riparian vegetation (except in the impoundment area), comprising mainly of alder trees, whose closed canopy overhung the stream (between 30 and 50% closure). Sampling programme Collections of invertebrates were made every two months at the study sites between December 1994 and October 1995. For this purpose we used a 350 µm mesh net and a constant sampling time of 4 min. The same collection was made at every site with the collector moving about in order to sample the major biotopes, while kick sampling. The contents of the hand-net were poured into a plastic box and quickly transported to the laboratory to sort the live macroinvertebrates, which were afterwards preserved in 70% ethanol. Wherever possible, organisms were identified to species level using the available keys (the main exceptions being the Diptera and Oligochaeta groups, which were differentiated only to family or sub-family level).
Statistical analysis The data collected on the invertebrates was analysed using three multivariate techniques. A preliminary and global analysis of all samples was performed through a hierarchical agglomerative clustering with group–average linking (WPGMA), based on a matrix of similarity obtained through the Bray-Curtis coefficient. To trace patterns created by regulation in each stream a non-metric multidimensional scaling (MDS) was computed, using the previous matrix of similarity. This ordination procedure constructs a plot by successively refining the positions of the points (by non-parametric regressions) until they match, as closely as possible, the distances or similarities of the input data matrix (Manly, 1994). The adequacy of the ordination representations of MDS were assessed by the stress value. Finally, classification applying a minimum spanning tree (MINSPAN) from chord distances allowed us to clarify data structure in 2D ordinations as the closeness of two sampling points does not imply that they differ in other dimensions (Digby & Kempton, 1987). This technique can be considered as a
55 divisive classification, but reveals object pairs responsible for the fusion of two clusters (Podani, 1994). In all cases, raw data was standardised by standard deviation (abundance values were replaced by standard deviates). In this way, we attempted to make the semi-quantitative sampling comparable between sites, or periods: also the measures of similarity of species abundance used are less affected by the most dominant or rarest species. We avoided the use of non-linear transformations in order not to introduce one more subjective criterion (as advised by Clarke & Warwick, 1994). To test for community differences between groups of reference and impacted sites, the study used the ANOSIM test (analysis of similarities). This technique computes a test statistic R, which falls approximately between 0 and 1, indicating the degree of discrimination between groups of samples (in this case reference/impacted sites). R calculation uses the underlying rank similarity matrix of WPGMA and MDS. The statistical programs used were PRIMER v4.0 beta (Clarke & Warwick, 1994) and SYN - TAX 5.0 (Podani, 1994). As well as using these procedures, two attributes of community structure, namely the Shannon-Wiener index of diversity and Pielou’s evenness index, were computed.
Figure 3. MDS ordination from R. Poio sites (samples with < 50 individuals were not considered). Note that axes are not labelled because plots can be arbitrarily scaled or rotated. The first letters represent the reach code followed by the month designation.
Results The dendrogram resulting from the WPMGA analysis of all samples of both streams (Figure 2) matches, in general, site groups belonging to the same river. We may conclude that different assemblages characterise each river, in spite of similar environmental conditions and geographical proximity. The exception was the downstream reach of the Balsemão (dw), from which samples show a more atypical pattern, being scattered in the diagram thereby revealing a greater degree of variability in community structure. Invertebrate data was treated by MDS for each stream (Figures 3 and 4). In the Poio (where samples with less than 50 individuals were discarded), no clear effects from regulation were shown and there was a lower degree of variability in community composition towards the end of spring/summer (samples from June and August). However, regulation impact was noticeable in the Balsemão, where the composition of benthic fauna below the dam differed from that above it. The samples from this sector exhibited, comparatively, a wider dispersion. The stress values (measuring the
Figure 4.
MDS ordination from all the R. Balsemão sites considered.
extent in which the original rank order of dissimilarities is preserved in the rank order of distances in MDS) were respectively, 0.12 and 0.16, therefore giving in both situations potentially useful two dimensional pictures (Clarke & Warwick, 1994). A clearer view of the relationship between the samples in this river was obtained through MINSPAN (Figure 5): The effects of
56
Figure 5. Minimum spanning tree classification of samples from R. Balsemão.
the dam, in producing radical changes to the benthic fauna below it, are shown clearly by the sequence of samples in the tree classification. We tried to gain a more detailed picture of the spatial and temporal gradients of the zoobenthos by using the multivariate test ANOSIM for a one way layout, applied to the similarity matrices corresponding to the previous MDS ordinations. The objective was to compute a test statistic reflecting the observed differences between sites in each stream, contrasted with differences among the six samples collected from each site over the one-year study period. Table 2 shows, for both cases, the values for the global R test (all samples from all sites), and the pairwise tests between sites, after 500 permutations. The significance level of the global test was 56.3% for R. Poio and 3.1% for R. Balsemão, enabling us to conclude that the null hypothesis (there are no differences among sites) could be accepted for R. Poio but rejected for R. Balsemão at the 5% level. For the latter river, the spatial variation exceeded the variation associated with sampling periods significantly, and the pair-wise tests confirmed that the lower reach was more distinct, particulary from the now impacted one (here the null hypothesis was rejected at the 0.5% level). A great contribution to the difference between points up and dw was the abundance at the last site of the mayflies Baetis rhodani, B. melanonyx, Ecdyonurus forcipula/angelieri, Epeorus torrentium and Heptagenia sulphurea, whereas the caddisfly Hydropsyche siltalai revealed an opposite pattern, with strong dominance at up. Diversity and equitability indices gave another vision of community changes (Figure 6). The reduction of diversity in the middle and lower reaches of the Poio, particularly in June and August (but also in February), suggested higher anthropogenic stress. In the
Figure 6. Monthly variation of diversity (H0 ) and equitability (e) along the three reaches of R. Poio and R. Balsemão.
57 Table 2. Tests R for analysis of similarity for each river based on the correspondent rank similarity matrices
R
R. Poio R. Balsemão
Global Test Significance level
−0.038 0.169
56.3% 3.1%
Pairwise tests up/dw
up/r R −0.055 0.078
Balsemão, despite considerable variation in community composition downstream of the weir, a modest decrease in species richness was found only in the month of August.
Discussion The situation documented by our study was contradictory, but interesting, in that invertebrate species composition was obviously modified by the R. Balsemão dam, but diversity decreased substantially only in the R. Poio. The irregular discharges in the Poio probably exceeded the environmental range needed to maintain high species diversity, as postulated by Ward & Stanford (1983a) and confirmed by Petts (1984). Transportation of fine sediments that fill interstitial spaces and also the occurrence of unstable substrata associated with discharge variability, were also likely contributors to the reduction of species diversity (Cobb et al., 1992). This was probably the cause of the reduction in species richness in the lower section of the Poio. However, diversity measures and species abundance distributions have to be analysed carefully, and associations between disturbance and diversity have been strongly debated issues. Boon (1988) observed that it is not possible to isolate single causal mechanisms for changes in diversity, as they are consequences of a chain of complex interactions. The works of Death & Winterbourn (1995), Death (1996) and Malmqvist & Englund (1996) found that their most unstable sites with more intensive diel fluctuations exhibited similar species abundance distributions to the stable ones, and that species richness peaked at sites of greatest stability, whereas evenness peaked at sites of intermediate stability. They concluded that, besides the level of disturbance, habitat patchiness has to be considered. In the R. Poio, there was neither evidence of species replacement below the dam, nor strong impoverishment of the benthic fauna
Level 61.9% 18.2%
R −0.044 0.291
Level 55.6% 0.4%
r/dw R −0.045 0.156
Level 57.1% 11.3%
in the reservoir itself, features associated with the impact of dams in larger rivers in Portugal (Fontoura & De Paw, 1991). The maintenance of substratum heterogeneity certainly explains the high resilience of the Poio system. Saltveit et al. (1987) reported that a permanent reduction in flow decreased the productive area available for stoneflies and that species typical of more lentic habitats may therefore increase in importance. This may also be the case at the site dw in the Balsemão. Its community was more stable than the correspondent one in the Poio, since flow peaks were less intense than in the previous case, which may explain the higher diversity, although with a different composition. We consider that for R. Balsemão the effects of regulation are mainly linked to the extended retention time of CPOM in the reservoir, eliminating the contribution of this material to the river below the dam, whereas there are periodical releases in the River Poio that prevent the accumulation of CPOM as noted elsewhere by Henricson & Sjöberg (1984). In these heterotrophic stream ecosystems of Northern Portugal, running through silicious bedrock, the structure and function of downstream communities are strongly regulated by the transportation of particulate organic food along the river (Cortes, 1992). Consequently, the continuous reduction in the provision of different fractions of POM gives rise to pronounced consequences below the reservoir. As reported in other studies (Benke & Wallace, 1980; Lillehammer & Saltveit, 1984; Hauer & Stanford, 1991), within the tailwaters there is generally a reduction of large particle feeders and/or an enhancement of filter feeders or sediment collectors. This was especially evident in the Balsemão when we consider Trichoptera group: shredders were more abundant and included more species at dw. Also, the net-spinning Hydropsyche siltalai exhibited high abundance, whereas it was virtually absent from the non-regulated upstream reach. The high densitiy of this species in dam tailwaters has
58 been frequently reported, and Boon (1987) linked its abundance to the synergestic effect of food supply and stable water flow. The decrease in the CPOM / FPOM relation, combined with the release of plankton from reservoirs with low level fluctuations, explains this situation, when considered alongside with an increase in algae production caused by a constant low flow release. The importance of epilithon development, associated with minimum base flows, on the trophic structure of the invertebrate community in regulated sections has been well documented by Valentin et al. (1995) and Blinn et al. (1995). Ephemeropterans, in particular, appeared in relatively higher numbers downstream of the Balsemão dam, either feeding on algae or as deposit collectors, but were scarcely represented in the upper reach. Canton et al. (1984) and Malmqvist & Englund (1996) concluded that the mayflies were strongly affected by fluctuating discharges, but also exhibited the most dramatic recovery. Armitage (1976) has already noted that the biological changes below dams have to be considered not only in terms of flow regulation, but in terms of the effect that hydrological variation has on the transportation of organic matter, possible organic enrichment and substratum stability. In fact, he found that when there was a reduction of stream flow the dominant benthic invertebrates used habitats and food created by dense algal or moss growths, as well the particles in the form of plankton from the reservoir. He also found that bottom fauna were encouraged by an increase in silt deposition. The life history characteristics also explain the quick recovery of some mayflies from environmental disturbance: high drift rates and flexible voltinism are generally pointed out as attributes that make these insects more able to withstand the impacts of flow regulation, allowing them to recolonise denuded habitats (Brittain & Eikeland, 1988; Brittain, 1991). We can conclude that the effects of regulation on small streams cannot be compared directly to those of large rivers impounded by hypolimnial release dams. In the latter, mainstream species are often displaced a considerable distance downstream and are replaced by major components of the riverine biota in the lower river (Ward & Stanford, 1983b; Hauer & Stanford, 1982; Hauer et al., 1989). The long term impact of dams on large rivers is parallelled by the changes in the temperature regime (Dolédec et al., 1996), a variable that is little affected by small head dams in low-order streams. The conspicuous effects of regulation on the streams studied, appears to be related to the relatively undisturbed substrate and, consequently, the
permanence of available refuges. However, different community responses were found in the two rivers (diversity versus species composition) because of differences in the patterns of energy flow and the regularity of water discharges. Considering this last aspect, five critical components of the flow regime regulate ecological processes in river ecosystems: the magnitude, frequency, duration, timing and rate of change of hydrological conditions (Ritcher et al., 1996; Poff et al., 1997). Therefore, it is not only hydrologic extremes below peak power hydroelectric dams, as on the Poio that affect aquatic species: flow stabilisation below water supply reservoirs (similar to the Balsemão dam) also result in artificial environments, with specific deleterious consequences. Poff et al. (1997) warn precisely of the need to consider modifications in each component of the flow regime when considering the diverse options in streamflow management or in river restoration. Finally, we must also take in to account that the variation in the abundance of the dominant taxa within shredders and collectors may provide useful tools when assessing the impact of stream regulation. References Armitage, P. D., 1976. A quantitative study of the invertebrate fauna of the River Tees below Cow Green Reservoir. Freshwat. Biol. 6: 229–240. Benke, A. C. & J. B. Wallace, 1980. Trophic basis of production among net-spinning caddisflies in a southern Appalachian stream. Ecology 61: 108–118. Blinn, D. W., J. P. Shannon, L. E. Stevens & J. P. Carder, 1995. Consequences of fluctuating discharge for lotic communities J. n. am. Benthol. Soc. 14: 233–248. Boon, P. J., 1987. The influence of Kielderwater on Trichopteran (Caddisfly) populations in the River North Tyne (Northern England). Reg. Rivers 1: 95–109. Boon, P. J., 1988. The impact of river regulation on invertebrate communities in the U.K. Reg. Rivers: Res. & Mgmt. 2: 389–409. Brittain, J. E., 1991. Life history characteristics as a determinand of the response of mayflies and stoneflies to man-made environmental disturbance (Ephemeroptera and Plecoptera). In Alba-Tercedor, J. & A. Sanchez-Ortega (eds), Overview of Strategies of Ephemeroptera and Plecoptera. Sandhill Crane Press, Gainesville, U.S.A.: 539–545. Brittain, J. E. & T. J. Eikeland, 1988. Invertebrate drift – a review. Hydrobiologia 166: 77–93. Canton, S. P., L. D. Cline, R. Short & J. W. Ward, 1984. The macroinvertebrates and fish of a Colorado stream during a period of fluctuating discharge. Freshwat. Biol. 14: 311–316. Castella, E., M. Bickerton, P. D. Armitage & G. E. Petts, 1996. The effects of water abstractions on invertebrate communities. Hydrobiologia 317: 97–107. Clarke, K. R. & R. M. Warwick, 1994. Change in Marine Communities: An Approach to Statistical Analysis and Interpretation. Plymouth Marine Laboratory, Plymouth, 160 pp.
59 Cobb, D. G., T. D. Galloway & J. F. Flanagan, 1992. Effects of discharge and substrate stability on density and species composition of stream insects. Can. J. Fish. aquat. Sci. 49: 1788–1795. Cortes, R. M. V. , 1992. Seasonal pattern of benthic communities along the longitudinal axis of river systems and the influence of abiotic factors on the spatial structure of those communities. Arch. Hydrobiol. 126: 85–103. Cortes, R. M. V., M. A. S. Graça, J. N. Vingada & S. Varandas de Oliveira, 1995. Stream typology and dynamics of leaf processing. Ann. Limnol. 31: 119–131. Death, R. G. & R. Winterbourn, 1995. Density patterns in stream benthic invertebrate communities: the influence of habitat stability. Ecology 76: 1446–1460. Death, R. G., 1996. The effect of habitat stability on benthic invertebrate communities: the utility of species abundance distributions. Hydrobiologia 317: 97–107. Digby, P. G. N. & R. A. Kempton, 1987. Multivariate Analysis of Ecological Communities. Chapman & Hall, London, 320 pp. Dolédec, S., J. Dessaix & H. Tachet, 1996. Changes within the Upper Rhône River macrobenthic communities after the completion of three hydroelectric schemes: Anthropogenic effects or natural change? Arch. Hydrobiol. 136: 19–40. Fontoura, A. P. & N. De Paw, 1991. Macroinvertebrate community structure and impact assessment of dams and impounding reservoirs in the Cavado River Basin (Northern Portugal). Verh. int. Ver. Limnol. 24: 1353–1359. Garcia de Jalón, D., M. Gonzalez del Tango & C. Casado, 1991. Ecology of regulated streams in Spain: An overview. Limnética 8: 161–166. Hauer, F. R. & J. A. Stanford, 1982. Ecological responses of hydropsychid caddisflies to stream regulation. Can J. Fish. aquat. Sci. 39: 1235–1242. Hauer, F. R. & J. A. Stanford, 1991. Distribution and abundance of Trichoptera in a large regulated river. Verh. int. Ver. Limnol. 24: 1636–1639. Hauer, F. R., J. A. Stanford & J. V. Ward, 1989. Serial discontinuities in a Rocky Moutain river, II Distribution and abundance of Trichoptera. Reg. Rivers 3: 177–182. Henricson, J. & G. Sjöberg, 1984. Stream zoobenthos below two short-term regulated hydro-power dams in Sweden. In A. Lillehammer & S. J. Saltveit (eds), Regulated Rivers. Universitetsforlaget, Oslo: 211–222. Ibañez, C., A. Rodrigues-Capitulo & N. Prat, 1995. The combined impacts of river regulation and eutrophication on the dynamics of the salt wedge and the ecology of the Lower Ebro River (NorthEast Spain). In Harper, D. M. & A. J. D. Ferguson. (eds), The Ecological Basis for River Management, John Wiley & Sons, New York: 105–144. Lillehammer, A. & S. J. Salveit, 1984. The effect of the regulation on the aquatic macoinvertebrate fauna of River Sudalslagen, Western Norway. In A. Lillehamner & S. J. Saltveit (eds), Regulated Rivers. Universitets Forlaget, Oslo: 200–210.
Malmqvist, B. & G. Englund, 1996. Effects of hydropower-induced flow perturbations on mayfly (Ephemeroptera) richness and abundance in north-Swedish river rapids. Hydrobiologia 341: 145–158. Manly, B. F. Y., 1994. Multivariate Statistical Methods, 2nd edn. Chapman & Hall, London, 215 pp. Muñoz, I & N. Prat, 1989. Effects of river regulation on the Lower Ebro river (NE Spain). Reg. Rivers: Res. & Mgmt. 3: 345–354. Petts, G. E., 1984. Impounded Rivers; Perspectives for Ecological Management. John Wiley and Sons, New York, 326 pp. Podani, J., 1994. Multivariate Data Analysis in Ecology and Systematics: A Methodological Guide to the SYN-TAX 5.0 Package. SPB Academic Publishing, The Hague, The Netherlands, 316 pp. Poff, N. L., J. D. Alan, M. B., Bain, J. R. Karr, K. L. Prestegaard, B. D. Richter, R. E. Sparks & J. L. Stromberg, 1997. The natural flow regime. BioScience 11: 769–784. Prat, N., I. Munõz, J. Camp, F. A. Camin, J. R. Lucena, J. Romero, J. Romero & M. Vidal, 1988. Seasonal changes in particulate organic carbon and nitrogen in the river and drainage channels of the Ebro Delta (NE Spain). Verh. int. Ver. Limnol. 23: 1344– 1349. Puig, M. A., J. Armengol, G. Gonzalez, J. Peñuelas, S. Sabater & F. Sabater, 1987. Chemical and biological changes in the Ter River induced by a series of reservoirs. In J. F. Craig & J. B. Kemper (eds), Regulated Streams: Advances in Ecology. Plenum Press, New York: 373–382. Richter, B. D., J. V. Baumgartner, J. Powell & D. P. Braun, 1996. A method for assessing hydrologic alteration within ecosystems. Conserv. Biol. 10: 1163–1174. Sabater, F., J. Armengol & S. Sabater, 1989. Measuring discontinuities in the Ter river. Reg. Rivers: Res. & Mgmt. 3: 133–142. Saltveit, S. J., J. E. Brittain & A. Lillehammer, 1987. Stoneflies and river regulation – a review. In Craig, J. F. & J. B. Kemper (eds), Regulated Streams. Plenum Press, New York: 117–130. Valentin, S., J. G. Wasson & M. Philippe, 1995. Effects of hydropower peaking on epilithon and invertebrate community trophic structure. Reg. Rivers: Res. & Mgmt. 10: 105–119. Vannote, R. L., G. W. Minshall, K. W. Cummins, J. R. Sedell & C. E. Cushing, 1980. The river continuum concept. Can. J. Fish. aquat. Sci. 37: 130–137. Ward, J. V. & J. A. Stanford, 1983a. The intermediate disturbance hypothesis: an explanation for biotic diversity patterns in lotic ecosystems. In Fontaine, T. D. & S. M. Bartell (eds), The Dynamics of Lotic Ecosystems. Ann. Arbor Science, Michigan: 47–63. Ward, J. V. & J. A. Stanford, 1983b. The serial discontinuity concept of lotic ecosystems. In Fontaine T. D. & S. M. Bartell (eds), The Dynamics of Lotic Ecosystems. Ann. Arbor Science, Michigan: 29–42.
60 Appendix 1. List of the macroinvertebrates present in the sampling sites of rivers Balsemão and Poio (+: presence; –: absence) Taxon
Tricladida Planariidae Polycelis felina Gastropoda Sphaeriidae Pisidium casernatum Pisidium milium
Balsemão up r dw
− − −
− + + − + −
Poio up r dw
+ − −
− − − − − −
Oligochaeta Lumbricidae gen. sp. Lumbriculidae gen.sp. Naididae gen. sp.
− + + + + + + + +
− − − + + + + + −
Hirudinea Erpobdellidae Erpobdella monostriata
− + +
+ − −
Hydracarina
+ + +
+ + +
Megaloptera Sialidae Sialis fuliginosa
+ − +
+ + −
− − − + + + −
− + − + − + −
Ephemoptera Baetidae Baetis sp. Baetis fuscatus Baetis melanonyx Baetis rhodani Centroptilum luteolum Centroptilum pennulatum Cloeon dipterum Caenidae Caenis luctuosa Caenis macrura Leptophlebiidae Callyarcis humilis Habroleptoides modesta Habrophlebia fusca Paraleptophlebia submarginata Thraulus bellus Heptageniidae Ecdyonurus aurantiacus Ecdyonurus dispar Ecdyonurus forcipula/angelieri Epeorus torrentium/sylvicola Heptagenea sulphurea
− − − − + − −
− − + + − − +
+ + + − + −
+ − − − + − −
− − − + + − −
− − − − − −
+ − + − +
− − − − +
+ − + + +
+ − + − −
+ − + − +
+ + + − −
− + + − −
− + − − −
− + + + +
− + − − −
− − − − −
+ + + − −
Appendix 1. contd. Taxon
Ephemerellidae Ephemerella ignita Drunella paradisini Ephemeridae Ephemera vulgata Siphlonuridae Siphlonurus cf. hispanicus Plecoptera Nemouridae Amphinemura cf. triangularis Protonemura beatensis Protonemura intricata Protonemura pyrenaica Nemoura cinerea Nemoura cf. obtusa Capniidae Capnioneura libera/mitis Capnopsis schileri Leuctridae Euleuctra geniculata Leuctra franzi Leuctra fusca Leuctra hippopus Leuctra cf. hispanica Leuctra maroccana Chloroperlidae Siphlonoperla torrentium Perlodidae gen. sp. Perlidae Perla marginata Taeniopterygidae Brachyptera gr. molinicorni Odonata Aeschnidae Boyeria irene Calopterygidae Calopteryx virgo Coenagrionidae gen. sp. Cordulegasteridae Cordulegaster boltoni Gomphidae Gomphus pulchellus Onychogomphus uncatus Onychogomphus forcipatus Coleoptera Dytiscidae Dytiscus sp.
Balsemão up r dw
up
− −
− −
+ +
+ +
+ −
+ −
+
−
−
−
−
−
+
+
+
+
+
+
− − − − − −
− − − − − −
+ − − − + −
− − + + − +
− − − − − +
+ + + − + −
− −
− −
+ −
− −
− −
− +
+ − − − − −
− − − − − −
+ − + + − −
− − − − − +
− − − − − −
− + − − + −
− −
− −
− +
+ +
− −
+ +
−
−
+
+
−
+
−
−
+
−
−
−
−
−
+
+
−
+ −
− −
− −
+ +
+ +
+ +
+
+
−
+
−
−
− + −
+ − −
− + −
− + +
− + +
− − −
−
+
−
−
+
+
−
Poio r dw
61 Appendix 1. contd. Taxon
Rhanthus sp. Agabus sp. Hydroporidae Graptodytes sp. Helodidae Helodes sp. Hydrocyphon sp. Helophoridae Helophorus sp. Hydraenidae Hydraena sp. Gyrinidae Orectochillus villosus Elmidae Oulimnius sp. Stenelmis canaliculata Dupophilus sp. Dryopidae Dryops sp. Trichoptera Limnephilidae Limnephilus guadarramicus Allogamus laureatus/ligonifer Potamophylax rotundipennis Chaeopteryx lusitanica Micropterna fissa/sequax Leptoceridae Setodes argentipunctellus Athripsodes braueri/tavaresi Mystacides azurea Brachycentridae gen. sp. Micrasema moestum Calamoceratidae Calamoceras marsupus Hydropsychidae Hydropsyche siltalai Hydroptilidae Hydroptilidae sp. Oxyethira sp. Lepidostomatidae Lepidostoma hirtum Psychomyiidae Lype auripilis Philopotamidae Philopotamus montanus Polycentropodidae Polycentropus flavomaculatus Polycentropus kingi/telifer Plectrocnemia laetabilis/inflata
Appendix 1. contd. Balsemão up r dw
up
Poio r dw
− −
− −
− −
− −
+ +
− −
−
−
−
−
+
−
− −
− −
− −
− +
− −
+ −
−
−
−
−
−
+
−
−
+
+
−
+
−
−
+
+
−
−
+ − −
− − −
− + +
+ − −
+ − −
+ − −
−
+
−
−
−
−
− + − + −
− + + − +
− + − − −
− − − + −
+ + + − −
− − + − −
− + + − −
− − + − −
+ + + − −
− + − + +
− + − − −
− + − − −
+
−
−
−
−
−
−
−
+
+
−
−
− −
− −
− −
+ −
− +
− −
−
−
−
+
−
−
+
−
−
−
−
−
−
−
+
−
−
−
− − −
− − −
+ + +
+ + +
− + +
− + +
Taxon up Rhyacophilidae gen. sp. Sericostomatidae Sericostoma sp. Thremmatidae Thremma tellae Heteroptera Aphelocheiridae Aphelocheirus occidentalis Corixidae Micronecta meridionalis Notonectidae Notonecta viridis Diptera Athericidae Atheryx sp. Athrichops sp. Chironomidae Chironomini gen. sp. Chironomus gr. Thumni Orthocladiinae gen. sp. Tanypodinae gen. sp. Tanytarsini gen. sp. Prodiamesa olivacea Corynoneura sp. Ceratopogonidae gen. sp. Dolichopodidae gen. sp. Empididae gen. sp. Tipulidae Eriocera sp. Simuliidae Simulium sp. Prosimulium sp. Eusimulium sp. Limoniidae gen. sp. Tabanidae gen. sp. Tipulidae gen. sp.
Balsemão r dw
up
Poio r dw
−
−
−
+
−
−
+
+
+
+
+
−
−
−
−
−
−
+
+
+
+
+
−
−
−
+
−
−
−
−
−
−
−
−
−
+
− +
− +
+ +
− −
− −
+ −
+ − + + + + + + − +
+ + + + + + + − − −
+ − + + + − + − + −
+ − + + + − − + + −
+ − + + + − − + − −
+ − + − + − − − − −
−
−
−
−
+
+
− − − − + −
− − − − + −
+ + + − − −
− − − − + +
− − − − − −
− − + + − −
