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Benthic macroinvertebrates have been used around the world as indicators of the biological quality of freshwater habitats. Because of the intensive deterioration of waterbodies as a result of different land uses, indicators are used for environmental monitoring, control and remediation. The aim of this study was to assess (1) the sensitivity of taxonomical metrics and (2) functional traits to select the most appropriate for evaluating environmental impacts on rivers with high salinity and (3) to propose a multimetric index based on the selected metrics. Information from a preexisting database on twenty-eight sites in the Salado River basin (Argentina) was used. One hundred and twenty-three metrics were calculated to assess sensitivity to different land uses along the gradient of habitat condition, from low-disturbed (reference), to medium-disturbed (agricultural and industrial) and high-disturbed (agricultural, industrial and urban). This gradient was defined by available information in original articles and by quantifying the percentage of the different land uses. Filtering collectors (%), Gathering collectors (%), Ostracoda density, Limnodrilus hoffmeisteri/Total density, Naididae (%), Tubifex/Total density and Pristina/Total density were the metrics that distinguished the different land uses along the gradient of habitat condition. These metrics were used to propose a macroinvertebrate multimetric index in saline rivers: Index of Benthic Invertebrates in Saline Rivers (IBIS). Thus, this study provides a useful tool for management and monitoring of saline rivers and diagnoses of salinized environments.

River-floodplain systems host very high biodiversity and provide a great variety of ecosystem services due largely to their high environmental heterogeneity, which is strongly dependent on spatial and temporal scales of observation. We aimed to describe the main patterns of environmental variation of the subtropical system of the Middle Paraná River at different scales of analysis using univariate and multivariate statistics. Physical, chemical and biological variables were analyzed during different hydro-sedimentological phases along four consecutive years in 31 aquatic environments. We considered four aquatic habitat types with different degrees of hydrological connectivity and water flow characteristics (major rivers, secondary channels, floodplain lakes permanently connected to the major rivers, and floodplain lakes temporarily connected to the major rivers) from two geomorphologic units with different drainage patterns: anastomosing and meandering. The environmental heterogeneity was mainly associated with the habitat types and relative contributions of lateral tributaries with different water qualities to each unit, in combination with the influence of the hydro-sedimentological regime. The heterogeneity of the system was significantly higher during low water than during high water phases. However, although the extreme flood reduced dissimilarities between habitat types within each geomorphologic unit, it increased differences between major rivers and between units. In conclusion, at different spatial scales, floods may simultaneously have a homogenization effect due to increased hydrological connectivity and a differentiation effect due to enhanced inputs of water from regions with variable geological characteristics and land uses. Finally, geomorphologic units can play a key role in maintaining the environmental heterogeneity during floods of high magnitude, even when land barriers among aquatic environments disappear. Fil: Mayora, Gisela Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Scarabotti, Pablo Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Schneider, Berenice. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Alvarenga Mariani, Patricio Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina

Purpose: The study was carried out in a wetland of the Middle Paraná River system, Argentina, in order to evaluate the processes associated with the decomposition of manure, which includes changes in chemical composition, nutrient release of manure, and colonization of invertebrates. We also compared the invertebrate assemblage that colonized manure with that present in the benthos of the wetland. Materials and methods: Nylon bags were filled with fresh cattle manure and anchored to the littoral zone of the wetland. Six bags were collected after 1, 2, 6, 14, 21, 28, 33, 55, and 79 days: three for invertebrate determination and the other three bags for determination of dry mass and chemical analyses. The nutrient content, cellulose, lignin, and total phenolic compounds of manure were determined. In addition, the leachate of manure was collected for nutrient analyses. Samples of the wetland benthic sediment were collected for benthic invertebrate determination and particle size analyses. Spearman rank correlation was used to evaluate the relationship between chemical compounds of manure and breakdown rate. Principal component analysis was used to explore invertebrate assemblage composition of manure and sediment during the experiment. Results and discussion: Limnodrilus, Dero, and Chironomus were dominant in the manure. Gatherer-collector was the dominant group in the manure, comprising almost 95 % of the total density of invertebrates. Breakdown rate was significantly related with nutrients, cellulose and total phenolics of manure. An ordination plot showed changes in invertebrate assemblages of manure and sediment samples over time. Conclusions: This study provides new insight on the importance of manure as a substrate for macroinvertebrate colonization. Cattle manure needs to be considered as a potential source of nutrients for aquatic systems and a substrate for invertebrate assemblages. Fil: Mesa, Leticia Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Maldini, Cecilia. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; Argentina Fil: Mayora, Gisela Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Saigo, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; Argentina Fil: Giri, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; Argentina

Biological monitoring requires a comprehensive baseline of assemblage distribution patterns and their environmental drivers. In this study we evaluated benthic macroinvertebrates in a regulated river, located in a semi-arid region, which has a seasonal flood pulse and is affected by several anthropogenic pressures. Taxonomic and trophic structures of benthic macroinvertebrate assemblages were analysed in terms of their longitudinal distribution, hydrological regime and environmental factors, including the effects of hydromorphology, riparian land use and water abstraction. Most taxa were generalists and classified in the collector–gatherer functional feeding group. A large taxonomic replacement was associated with hydromorphological characteristics. Local environmental variables were critical for macroinvertebrate assemblages. There was significant temporal variability regarding seasonal flood pulse. Water abstraction for irrigation had a strong effect on assemblage structure. We suggest some challenges and issues for successful implementation of biomonitoring tools in the Dulce River, related primarily to high spatiotemporal variability.

Macrophyte assemblages are composed of species with different life forms and various ecological functions. Our aim was to investigate the potential environmental determinants of changes in the biomass of individual life forms and of the composition of the macrophyte assemblage in terms of life forms diversity. We sampled 23 waterbodies at low and high water levels in the Middle Paraná River floodplain. Macrophyte biomass samples were collected and classified in terms of life forms. We performed a redundancy analysis using the biomass of the various life forms to assess the importance of environmental variables to the composition of macrophyte life forms. Linear regressionswere applied to investigate the environmental determinants of the biomasses of individual life forms. The degree of connectivity and the combination of depth, hydrology and nitrate were the main determinants of the composition in terms of life forms. The biomass of each individual life form was explained by different combinations of environmental variables, but the connectivity was the most important one. Our study shows that groups of species with similar life forms respond to environmental factors in particular ways, which might alter the biomass composition of life forms. Given that the ecosystem functioningdepends on the functional characteristics of local communities, our findings about the relation between environmental changes and the community composition in terms of life forms (or functional composition) can be a helpful tool for predicting changes on ecosystem processes (such as nutrient cycling) against possible future scenarios. Fil: Schneider, Berenice. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Cunha, Eduardo R.. Nucleo de Posquisas Em Limnologia; Brasil Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Thomaz, Sidinei Magela. Universidade Estadual de Maringa; Brasil

The middle and lower sections of most large rivers have fine-grained bed sediments, which may have a strong influence on the functional and taxonomical structure of benthic invertebrates. Based on results from several studies by the authors on the faunal assemblages and habitat structures of the Paraguay-Paraná River system (Brazil, Paraguay, Argentina), from European (Rhine, Loire) River systems, and data from the literature, this review identifies general patterns which appear to have a global character. At one hand the invertebrate assemblages largely differed between main channel and the corresponding floodplain habitats in different sections, and also the floodplain habitats along the river channel revealed great differences in their biodiversity. At the other hand there was a remarkable homogeneity among the main-channel sections within and even between river systems. We consider physical habitat features as the crucial variable responsible for these patterns. In cross sections from the main channel towards the floodplain habitats, grain size, organic matter content and oxygen supply change dramatically, and different floodplain habitats along the same river system may have different successional stages even at small geographical distances. The sandy structure of potamal habitats (including underwater dunes), however, provides a set of habitat features characterized by continuously changing sediment structures with well-defined grain sizes, low organic matter contents, and good oxygenation, which force a set of adaptations by the invertebrates that limits but stabilizes the diversity of invertebrates in these large river sections. A better understanding of the ecohydrological interactions between habitat dynamics and benthic invertebrates is needed to improve sustainable river ecosystem management. We discuss the nonrecovery of large benthic invertebrate species in the lower section of large rivers after improvement of the water quality in the context of these ecohydrological features. Conclusions are drawn for river restoration. Fil: Wantzen, Karl Matthias. Université François-Rabelais de Tours; Francia Fil: Blettler, Martin Cesar Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Amsler, Mario Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina Fil: Bacchi, Michel. Université François-Rabelais de Tours; Francia Fil: Ezcurra, Ines Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Drago, Edmundo Carlos E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina

To explore temporal variation in trophic relationships of benthic invertebrates in the Middle Paraná River floodplain, we performed stable isotopes analysis (SIA) in two lakes with contrasting morphologies during both dry and flooding periods. Lake 1 is permanently connected, large and deep with a narrow aquatic–terrestrial transition zone (ATTZ), and Lake 2 is temporarily connected, small and shallow with a wide ATTZ. The source contribution analysis showed that macrophytes and sediment particulate organic matter are important basal resources. We found sharp temporal variations with regard to gatherer–collectors in Lake 2, being sediment particulate organic matter the most important source during dry period. However, during flooding, macrophytes and epiphyton increased their importance. Our results reveal temporal variations in trophic interactions, suggesting that hydrologic and morphologic characteristics of water bodies can be important factors determining food web structure. Besides, we provide evidence from floodplain lakes of the Middle Paraná River, which contradicts the general idea that algae is the main carbon source in floodplain rivers. Fil: Saigo, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Wantzen, Karl Matthias. Université François Rabelais; Francia

We introduce here the term "River Culture" to delineate an eco-social approach to mitigate the biological and cultural diversity crisis in riverscapes. It is based on the insight that current environmental change endangers both, biological and cultural diversities in rivers and their basins, and those activities to improve ecosystem functions, biodiversity and capacity of the biological species to evolve will have a similarly positive effect on human cultural diversity. "River Culture" has two dimensions, including (a) the influence of the biophysical setting of rivers (specifically, their pulsating flow regimes and their biological features) on the expression of elements of human culture in general and (b) the aspect of "learning from the river" for the development of technologies and management options that are targeted to maintain and improve ecosystem functions and diversity in a more sustainable way. The River Culture approach, as given in this concept and discussion paper, is preliminarily based on five tenets: (1) Reset values and priorities in riverscape management in favor of human wellbeing and a harmonious coexistence of man and riverscape; (2) Live in the rhythm of the waters, i.e. adapt management options in accordance with the hydrological dynamics rather than fighting against them; (3) Transform traditional use of rivers into modern cultural activities and management options; (4) 'Ecosystem bionics': by copying survival strategies of flood-pulse adapted organisms novel forms of human use can be developed; (5) Make the catchment (river basin) the geographical base unit for all kinds of political decisions in landscape management. Fil: Wantzen, Karl Matthias. Universite de Tours; Francia Fil: Ballouche, Aziz. Universite D'angers; Francia Fil: Longuet, Isabelle. Unesco; Francia Fil: Bao, Ibrahima. Universite Gaston Berger de Saint-louis; Senegal Fil: Bocoum, Hamady. Institut Fondamental D'afrique Noire; Senegal Fil: Cissé, Lassana. Direction Nationale Du Patrimoine Culturel; Malí Fil: Chauhan, Malavika. Himmotthan Society; India Fil: Girard, Pierre. Universidade Federal de Mato Grosso; Brasil Fil: Gopal, Brij. Centre For Inland Waters In South Asia; India Fil: Kane, Alioune. Universite Cheikh Anta Diop; Senegal Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Nautiyal, Prakash. Hemwati Nandan Bahuguna Garhwal University; India Fil: Teixeira, Paulo. Universidade Federal de Mato Grosso; Brasil Fil: Zalewski, MacIej. University Of Lodz; Polonia

The habitat heterogeneity generated and sustained by the connectivity of floodplain habitats, the seasonal flood pulse, and the variability of the physical structures typically found in floodplains of large rivers results in a variable space–time mosaic of water sources that results in a high biodiversity of the river-floodplain system. In order to assess the implications of natural connectivity and the heterogeneity on the patterns of macroinvertebrate assemblages at different spatial scales, monthly samplings in six different mesohabitats (lakes with different hydrological connection and secondary channels with permanently and intermittent flow) of the Parana River floodplain were performed from April 2005 to March 2006. The mesohabitats had different granulometry and detritus composition of their bottom sediments. They also had different conductivity, transparency, and depth in relation to the different connectivity degrees. Mesohabitats differed in the abundance of macroinvertebrates of different taxonomic groups and diversity. The environmental variables were correlated to the patterns of macroinvertebrate abundance, with dominance of different species of annelids and mollusks at the patch, mesohabitats, and island scales. An alpha diversity gradient from the isolated lake (65 taxonomic units) to the secondary channels (25 taxonomic units) was obtained. The analyzed mesohabitats showed a high taxa turnover, with high values not only among the mesohabitats located in the different islands, but also among the mesohabitats in relation to different connectivity degrees. The mesohabitats showed negative co-occurrence of macroinvertebrate assemblages. The spatial heterogeneity, sustained by the connectivity degree, played a key role in structuring benthic assemblages at different scales, positively influencing the regional diversity.

This chapter focuses on invertebrates of seasonal floodplains of large neotropical rivers. These huge wetlands are characterized by an annual monomodal flood pulse with extensive wet-and-dry phases that act as a strong selective agent on life-cycle strategies and physiological adaptations of resident biota. Invertebrates play an important role in the organic matter transfer between the floodplain and the river main stem. There is a remarkable contrast between the low-diversity and rather evenly distributed invertebrate assemblages of the sandy river channels of lowland neotropical rivers, and the high beta biodiversity in their floodplains. River management should maintain the floodpulse that enables the high functional diversity of floodplains and their invertebrates.

Functional classifi cation of animals is necessary to enhance the predictive power of food web models. However, while there is a large database for functional classifi cation of benthic invertebrates (Functional Feeding Groups, FFG) in the temperate zone, the attribution of individual species of riverine invertebrates is still in its infancies in the Neotropical Region. Diff erent authors hypothesized that diet breadth was larger in the Tropics, however detailed analyses are scarce. In the present study we aimed at classifying dominant benthic taxa of the Middle Paraná River floodplain (Argentina) into trophic guilds by diet and niche overlap analysis. We sampled twelve taxa of benthic invertebrates from a fl oodplain lake during low water season and performed a gut content analysis as a baseline for FFG classifi cation. We also used available diet information of other common taxa for statistical analysis. Then, we compared the variance of niche overlap, using Pianka?s index, with that of simulated null model. After that we grouped taxa using Morisita similarity index with a threshold of 0.6 and compared niche overlap with null models within and between FFGs. Observed variance of niche overlap was greater than expected by chance, confi rming the presence of FFGs among analyzed taxa. Considering trophic similarity of species, we identified four FFGs: collectors, omnivores, herbivores and predators. Niche overlap was greater than expected by stochastic null models within FFGs, and smaller between FFGs. Nearly one third of analyzed taxa were classified in a diff erent FFG than their congeners of the Holarctic region. This result indicates that classifications performed in the Holarctic region should be used with care in the Neotropical region, even in subtropical systems. Fil: Saigo, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Wantzen, Karl Matthias. Cnrs Umr Citeres, Universite François Rabelais; Francia

During a broad study of invertebrate colonization in marginal fluvial wetlands of the Middle Parana River in Argentina, cyst formation was observed in two of the 26 species of aquatic oligochaetes identified from the study—Dero multibranchiata Steiren, 1892 (Tubificidae, Naidinae), andTrieminentia corderoi (Harman, 1969) (Opistocystidae). All specimens of the two species in which cyst formation was observed had been collected after drying conditions ranging from 14 to 28 days. A clitellum was not observed in any of the specimens collected. Lengths of specimens ranged from 0.88 mm to 2.84 mm inDero multibranchiata and 2.25 mm to 2.40 mm inTrieminentia corderoi. The development of protective cysts byDero multibranchiata andTrieminentia corderoi, and perhaps many other species of aquatic oligochaetes, appears to be an adaptive strategy enabling them to survive drought in temporary wetlands, recolonize freshwater habitats upon inundation, and disperse both laterally and downstream with rising water levels in wetlands and streams.

This paper presents the first study of the benthic invertebrate assemblages of the upper section of the Paraguay River, a major tributary to the Pantanal wetland in Brazil. Thirty-eight sites were sampled along a 200 km section below the city of Caceres in November 2000. Sixty-nine species and morphospecies were identified, which were dominated by Oligochaeta and Chironomidae. Mean density of benthic invertebrates varied between 72 and 10 354 m−2 in the meandering sector of the river, 3611–49 629 m−2 in the straight–transitional sectors, 682–5962 m−2 in the floodplain lakes, and 1704–2208 m−2 in floodplain channels. Highest densities were attained in sand-gravel sediments dominated by the psammophilous oligochaete Narapa bonettoi. The Shannon diversity index ranged from 0.75 to 2.08 and was highest in floodplain lakes. Statistical analysis (UPGMA and CCA) revealed that benthic assemblages in the floodplain habitats were clearly distinct from the riverine habitats. In the river channel, the habitats were distinguished by grain size while the floodplain habitats were mostly determined by current and silt-clay concentration (floodplain channels) or by organic matter concentration (floodplain lakes). Conservation efforts in the Upper Paraguay area should aim to maintain the flood pulse as a permanent source of spatial and temporal habitat heterogeneity. Copyright © 2005 John Wiley & Sons, Ltd.

We studied the composition and spatial structure of benthic invertebrate assemblages and their physical and chemical environment on a 331 km long section of the Lower Paraguay River between Asuncion (Paraguay) and the river's confluence with the Parana River near Corrientes (Argentina). Applying the same methods used in former studies in the Upper Paraguay and Parana Rivers, we sampled bottom fauna, bed sediments and water at ten riverine stations, two tributaries, and six floodplain lake sites. Seventy-six taxa, mostly oligochaetes (18 species) and chironomids (17 species), were identified. There was a clear distinction between central sites, river banks, and floodplain habitats. Highly significant regressions between sediment composition and biotic parameters were obtained (clay/diversity, R = 0.60, p < 0.0001; silt/diversity, R = 0.61, p < 0.0001; organic matter/diversity, R = 0.63, p

Food webs in floodplain ecosystems may be based on a variety of aquatic, terrestrial or amphibiousfood resources. Here, we determined which of the basal resources mostly contribute to the food websin a floodplain lake of the Middle Paraná River using isotopic composition of C and N (ı13C and ı15N)of potential food sources in the Paraná floodplain (Argentina). We analyzed if organic matter sourcesisotope of C and N differ between flooding and low water seasons, and analyzed the isotopic niche repre-sentations of consumers in order to characterize niches width and intraguilds overlapping. To estimatethe contribution of different sources of carbon to primary consumers, we measured the stable isotopiccompositions of bottom sediment organic matter, coarse particulate organic matter, biofilm, suspendedparticulate organic matter, epiphyton, phytoplankton, C3 and C4 macrophytes and riparian tree leaves,benthic macroinvertebrates, aquatic orthopterans and fishes in dry and flooding seasons. The packagesStable Isotope Analysis and the Stable Isotope Bayesian Ellipses algorithm in R were calculated to comparethe C and N isotopic variability between the primary consumers and their sources. The energy sourcesavailable for benthic organisms mainly originated from autochthonous sources based on the C3 photo-synthesis pathway. The isotopic signatures of sources and primary consumers did not differ significantlybetween low and high water seasons. Our results demonstrated a higher contribution to primary con-sumers of C3 macrophytes and low contributions of C4 for herbivores; biofilm and benthic organic matterfor gatherer collectors (Oligochaeta and Chironominae); epiphyton for ephemeropterans, amphipods andfishes, whereas biofilm was the most important source for mussels. Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Saigo, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Zilli, Florencia Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Capello, Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Devercelli, Melina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Montalto, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Paporello, Graciela Eulalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Wantzen, Karl Matthias. Université François Rabelais; Francia

Orthoptera assemblages associated with macrophytes of floodplain lakes of the Paraná River. The Orthoptera assemblage composition varies considerably, depending on habitat type. This study examines the spatiotemporal relationship between plant diversity, hydrometric level, environmental variables and the Orthoptera richness and abundance in floodplain lakes connected permanently or temporarily with the main channel of the Paraná River. The grasshoppers were collected fortnightly (April 2006-May 2007). A total of 17 species were recorded and classified according to their frequency of occurrence in constant (7), accessory (4), or accidental (6) species. In the two lakes, the greater species richness and abundance was recorded in summer, thereby coinciding with the highest water level of the Paraná River. The most significant correlation between the orthopteran richness and abundance was with the water level. The aquatic plant richness was significantly different between the lakes, but the vegetation was dominated by Eichhornia crassipes (Mart.) Solms. (Liliales, Pontederiaceae). The lake, which was connected permanently, presented the highest values of diversity and abundance, proving to be a more diverse assemblage. The beta diversity was higher in the temporary connected lake than in the permanently connected one. The orthopterans assemblages were different between the lakes, Cornops aquaticum and Tucayaca gracilis were the species that contributed more to the level of dissimilarity. C. aquaticum was more representative in the lake temporarily connected, while T. gracilis in the permanent connected one. The water level of the Paraná River and the connectivity of the floodplain lakes play an important role to explain the abundance and richness of their orthopteran assemblages., Centro de Estudios Parasitológicos y de Vectores

Obtaining unbiased samples of aquatic and terrestrial invertebrates from wetlands provides unique challenges due to the varied life history strategies of invertebrates as well as the heterogeneity present within a wetland. Many sampling devices are useful in more than one sampling environment within a wetland but the effectiveness of most methods varies among and within wetlands as well as between users. In this chapter, we emphasize field collecting techniques and address laboratory sorting methods. When possible, the advantages and disadvantages of each method are listed and suggestions are provided to reduce bias and unwanted variability in sample collection. Sampling devices for benthic (grabs, single and multiple cores, nets, and artificial substrate), water-column (open cylinder, emergence trap, activity trap, sweep net), epiphytic (box samplers, quadrat samplers), flying terrestrial (aerial net, flight intercept trap, light trap, malaise trap), and non-flying terrestrial (sweep net, aspirator, vacuum sampler, Berlese-Tullgren funnel, mist net) invertebrates are presented and discussed.

The flood pulse regime and the hydrological connectivity determine the lateral bidirectional exchanges of water, chemical compounds, and biota between the river and the floodplain habitats. The primary goal of the present research was to analyze the effect of water flow on macroinvertebrates in two water levels in a lateral connectivity gradient, from the main channel through a connection channel to a permanently connected lake. We tested the hypothesis that the water flow from the main channel to the floodplain habitats during high water level causes a decrease in beta diversity between the sites, increasing similarity in the system. To test this hypothesis, we sampled a river–floodplain–lake system of the Middle Parana River during two water levels, and analyzed the spatial and temporal turnover of species between sites and habitats. Local physical characteristics, such as depth, benthic particulate organic matter, and grain size of bottom sediments influenced assemblage composition. Taxa richness, density, and Shannon diversity differed among habitats within the river–lake system, but did not show significant differences between water levels. Richness, density, and diversity were higher in the lake and the connection channel than in the Parana River bank. Beta diversity was significantly higher during high water period. During low water period, benthic assemblage composition was homogenized, as reflected by the lower values of species turnover between the sites situated in the main channel–lake corridor during this phase. The lateral bidirectional exchanges among the habitats are essential for maintaining the specific invertebrate diversity of large river corridors. Fil: Mesa, Leticia Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Montalto, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Zilli, Florencia Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina

This study synthesizes the results from ten years (1978–1988) of research in lotic environments of the middle Parana River. We elucidate the important environmental factors that determine differences in quality and structure of the benthos among the main channel, secondary channels and tributaries, and we determine species or descriptive associations of the different types of environment.

The benthic invertebrate assemblages and functional feeding groups in different mesohabitats of the Middle Parana River–floodplain system were analyzed. Benthic invertebrates and bottom sediments were sampled in a secondary channel (center and bank mesohabitats), a temporal marginal fluvial wetland adjacent to the river, an isolated lake and a connected lake during low water level. Cluster analysis of average invertebrate densities based on the Bray Curtis dissimilarity index yielded a group composed by the mesohabitats with higher species richness, the floodplain lakes, banks mesohabitats and the wetland. The center mesohabitat of the main channel characterized by sandy sediments with low organic matter content and the lowest invertebrate densities and species richness was classified separately. Alpha diversity increased from the center mesohabitat (6 taxa) to the adjacent wetland (71 taxa), and were similar between the floodplain lakes (24 and 22 taxa) and the river bank mesohabitat (24 taxa). Gamma and beta diversities (Whittaker index) were 92 and 2.19, respectively. The highest turnover of taxa was between the river and the other mesohabitats and the lowest between floodplain lakes. Detrended correspondence analysis (DCA) showed a clear separation of wetland and banks from other mesohabitats (axis 1 and 2 explained 52.25% variance) explained by shredders and collector-filterers. The other mesohabitats were arranged in a gradient from the main channel mostly related to collector-gatherers to the connected lake and the isolated lake that were mostly characterized by predators and scrapers. The invertebrate assemblage complexity and functional feeding groups composition increased in the lateral dimension, from the center of the main channel to the temporal marginal fluvial wetland due to the influences of the spatial heterogeneity caused by different sources of organic matter inputs.

Simple and multiple correlations among physical and chemical parameters and densities of the dominant Oligochaete species were calculated for various channels of the middle Parana valley and its tributaries. Paranadrilus descolei Gavrilov, 1955, was observed in rivers with average depth and current velocity, mud-clay sediments, and low conductivity. Tubifex tubifex f. blanchardi Vejd., 1891, was found in channels of low depth, current velocity and discharge but with high conductivity. Limnodrilus hoffmeisteri Claparede, 1862, and Aulodrilus pigueti Kowalewski, 1914, were ubiquitous species. Narapa bonettoi Righi and Varela, 1983, was typical of rivers highest in depth, current velocity, and discharge with sandy sediments and low conductivity.