This study combined several features of acoustic and electromagnetic (EM) waves-based devices including sub-bottom profiler (SBP), side-scan sonar (SSS) and ground penetrating radar (GPR), and in situ sediment data to study responses of bottom sediments after carp removal in Lake Wingra. In 2007, i.e., before carp removal, macrophytes only grew to a water depth of 2 m. Meanwhile, GPR data showed no visible sublayer in vegetated regions, while SBP data revealed a loose and fluffy sediment layer in unvegetated regions, easily affected by wave or current motions. The field data showed that suspended sediment concentrations (SSC) were much greater in unvegetated regions than those in vegetated regions during a one-day wind event, and the resuspended sediments could remain suspended in the water column for two days. In 2009, i.e., after more than half (51%) of carp were removed, the fluffy sediment layer recognized by SBP became thinner or even disappeared, and both SBP and SSS results showed that submerged macrophytes started growing in deeper water. In situ sediment data presented that bulk sediment density and critical shear stress became greater, and bottom sediments consolidated and were harder to be resuspended. Secchi depth collected between 2008 and 2010 was greater than that in the previous 10 years, indicated clearer water state. In short, the fluffy sediment layer because of carp activities may be the main source for suspended sediments to deteriorate water quality. Removal of carp is crucial for stabilizing bottom sediment and improving water clarity in this small lake.

A new genus (Callibaetoides) and species (Callibaetoides caaigua) of Baetidae (Ephemeroptera) is described based on nymphs and adults of both genders collected in forested areas of Amazonia and Mata Atlântica biomes. The nymphs were collected from leaf packs accumulated in the backwaters of small streams. The genus and species can be easily distinguished from other members of the family in South America by the following combination of characteristics: male and female imagos with costal process of hind wing centrally located and strongly projected; marginal intercalary veins long and paired in male imago; nymphs with deep medial emargination of labrum, maxillary palp three segmented and third segment of labial palp quadrangular.

The role of heterotrophic biofilm of water–sediment interface in detoxification processes was tested in abiotic and biotic conditions under laboratory conditions. Three toxicants, a herbicide (Diuron), a fungicide (Dimethomorph) and an insecticide (Chlorpyrifos-ethyl) have been tested in water percolating into columns reproducing hyporheic sediment. The detoxification processes were tested by comparing the water quality after 18 days of percolation with and without heterotrophic biofilm. Tested concentrations were 30 μg.L−1 of Diuron diluted in 0.1% dimethyl sulfoxide (DMSO), 2 μg.L−1 of Dimethomorph and 0.1 μg.L−1 of Chlorpyrifos-ethyl. To characterise the detoxification efficiency of the system, we performed  genotoxicity bioassays in amphibian larvae and rotifers and measured the respiration and denitrification of sediments. Although the presence of biofilm increased the production of N-(3,4 dichlorophenyl)-N-(methyl)-urea, a metabolite of diuron, the toxicity did not decrease irrespective of the bioassay. In the presence of biofilm, Dimethomorph concentrations decreased compared with abiotic conditions, from 2 μg.L−1 to 0.4 μg.L−1 after 18 days of percolation. For both Dimethomorph and Chlorpyrifos-ethyl additions, assessment of detoxification level by the biofilm depended on the test used: detoxification effect was found with amphibian larvae bioassay and no detoxification was observed with the rotifer test. Heterotrophic biofilm exerts a major influence in the biochemical transformation of contaminants such as pesticides, suggesting that the interface between running water and sediment plays a role in self-purification of stream reaches.

Limnocharis flava, a species native to tropical America, is naturalized as a noxious weed in Sri Lanka, India and some other Southeast Asian countries. It is widespread in flood plains, wetlands and agricultural wetlands resulting in poor drainage. In the current study, the influence of different water conditions on growth, development and morphology of L. flava was investigated. Plants were grown on experimental pots filled with wetland soil, simulating flood, standing water and dry conditions. The highest biomass and relative growth rate was observed in the plants grown at flood conditions, while the lowest total biomass content was observed in the plants grown at dry conditions. L. flava showed morphological adaptations in different water conditions, including significant differences in the relative biomass allocation for root, petioles and leaves. Root biomass significantly increased in flooded conditions. Observed decrease in leaf area and increase in leaf total chlorophyll content may facilitate the survival in dry conditions. Plant mortality and no production of inflorescence may indicate the difficulty in surviving at dry conditions. No significant difference was observed between the plants grown under ‘high flood’ conditions and ‘low flood’ conditions. Overall, L. flava showed difficulties to grow under dry conditions, but performed well under other conditions.

Restoration projects in wetlands are becoming increasingly frequent to recover or to create new aquatic ecosystems, after the significant impact and high degradation they have undergone. In the present study, we focused on the changes in the zooplankton community in a permanent peridunal pond where a restoration was carried out in order to increase its surface as a main objective. For this purpose, the community was compared before and after the restoration (15 years before, the year after and between 3 and 6 years later). Significant changes in environmental variables were observed after pond restoration: chlorophyll a concentration decreased and dissolved oxygen increased. Substantial modifications in the aquatic community were also observed, since species richness and diversity increased after restoration: a large number of new species appeared (84%, mainly cladocerans), from external or internal sources. In addition, zooplankton community structure and composition changed from a low specific richness community copepod-dominated in density (mostly nauplii) before restoration, to another one with higher richness and different composition co-dominated in density by rotifers and nauplii, but with greater abundance of cladoceran species. All this suggests an important change in the ecological functioning of the pond, mainly produced by improvement in habitat heterogeneity and water quality after restoration.

The genus Nanocladius Kieffer, 1913 (Diptera: Chironomidae: Orthocladiinae) has been frequently found in aquatic habitats of the Neotropical region. However, until now only one species was described living symphoretically on Ephemeroptera and no free-living species has been cited or formally described from the region. In the present study, two new species of Nanocladius are described and figured as male, pupa and larva: N. communis and N. longispicula. The specimens were collected from different streams in Brazil and are the first recorded species of the genus to the country.

Invertebrate drift results from several factors, including accidental dislodgement from the substratum, interaction with other invertebrates and predators, and changes in water quality, discharge and current velocity. We evaluated the degree to which flow fluctuations from dam releases altered the daily and seasonal invertebrate drift patterns in a tropical river. We collected macroinvertebrates during fixed flow rates (323 m3.s−1 in the wet season and 111 m3.s−1 in the dry season) and when peak flows fluctuated (378–481 m3.s−1 in the wet season and 109–173 m3.s−1 in the dry season) in 2010. Of the 31 924 organisms collected, 8872 individuals and 43 taxa were collected in the wet season and 23 052 and 32 taxa were collected during the dry season. Seasonality had a strong influence on invertebrate assemblage composition and structure in the drift. During fixed flow periods, drift densities were greatest in the dry season and drift taxonomic richness was greatest in the wet season. In the wet season, fluctuating flows increased nocturnal drift density and richness, but decreased diurnal richness; in the dry season, fluctuating flows decreased drift densities and diurnal richness. In conclusion, the daily and seasonal invertebrate drift patterns are influenced by dam operations that alter flows and this knowledge can be used to reduce the downstream effects of dams.

Temperate streams flowing through deciduous forests derive most of their energy and carbon from allochthonous organic matter supplied by the riparian vegetation mostly during the autumnal litter fall. The decomposition of this coarse particulate organic matter (CPOM) supports the aquatic foodwebs throughout the year. During the decomposition process, part of the CPOM is converted into fine particulate organic matter (FPOM). In this study, we assessed the relationships among decomposition rates of a dominant litter species, oak leaf litter (estimated by the litter bag approach in the presence and absence of macroinvertebrates), benthic CPOM stock and FPOM flux over 12 months in a temperate mountain oligotrophic stream. We also assessed the relationship between these organic matter variables and environmental variables over the same period. As expected from the seasonality in temperature, litter decomposition rates varied over the year and were positively correlated with water temperature and dissolved phosphorus concentration. However, benthic CPOM stock did not significantly change over the year; the higher rainfall in winter and the higher litter decomposition in spring might have compensated for each other in keeping the CPOM stock fairly constant year round. FPOM flux was positively correlated with litter decomposition rates as expected, and this relationship was primarily driven by the activities of detritivores and not of microbes. We can anticipate changes in the carbon cycle, both locally and downstream, if oligotrophic montane streams are subjected to temperature increases (e.g., due to removal of riparian vegetation or in a global warming scenario) and nutrient enrichment from effluents or agricultural activities.

Ammocoetes of sea lamprey (Petromyzon marinus Linnaeus, 1758) from an assumedly pristine tidal freshwater habitat were used for determination of metal levels and accumulation patterns with size. The individuals were collected during the winter of 2011 in river Minho (Iberian Peninsula, Southwest of Europe) and the levels of metals (Cd, Cu, Cr, Fe, Pb, Mn and Zn) in the whole body were analysed by atomic absorption spectrometry. Fe was the metal with highest levels (maximum of 1438 ppm), while Cd and Pb were the lowest accumulated elements (overall means of 0.093±0.065 ppm and 0.259±0.094 ppm, respectively). Larger ammocoetes seemed prone to accumulate Cu, Fe and Mn (P<0.05). Pb and Zn levels also seemed to increase with ammocoetes size; however, statistical differences were not found between size classes (P>0.05).

Saint-Augustin Lake is an urban lake in Québec, Canada that has been subjected to long periods of direct human impact, mainly due to agricultural and urban activities, with great changes in trophic status and chemistry occurring within the last few decades. In 2009, during an examination of the lake bottom substrate, the presence of the invasive species Cipangopaludina chinensis (Reeve, 1863) was found on floor bottom sediments. The gastropods soft tissues were mineralized and analyzed by ICP-OES. The purpose of this study was to estimate concentrations of heavy metals in C. chinensis, describing the relations of these values with the sediment metal. In gastropod soft tissues the overall common trend in the heavy metal concentrations was revealed in the following order: Fe>Mn>Zn>Cu>As>Ni>Pb>Cd>Cr. Biota-sediment accumulation factors (BSAFs) have shown that C. chinensis cannot be used as a bioindicator of heavy metal pollution and exposure in the Canadian lakes where it is present. In fact, while the sediments of Saint-Augustin Lake are characterized by high metal concentrations, C. chinensis does not have high bioaccumulation factors (BSAFs <1.0). By literature comparison with other aquatic organisms in polluted ecosystems at different latitudes it was possible to affirm that the concentrations of Fe, Mn and Zn in C. chinensis tissues are considerable if compared with these sites.

The colonization of periphytic algae in a temperate floodplain was studied in Lake Sakadaš, a part of a fluvial floodplain along the Danube River. An in situ investigation, using artificial substrata, was started after extremely high spring flooding and was carried out during long-lasting summer floods (July–August 2010). The physical and chemical environment was variable and large stands of metaphyton, submersed and floating macrophytes were spread along the lake. The periphyton development was initiated on the first day of exposition and algal abundance increased exponentially till day 27. Directional changes in the relative abundance of algal species, shown by the results of the non-metric multidimensional scaling, indicate a pattern of short-term sequences in algal colonization. The initial attachment of planktonic cyanobacteria and unicellular diatoms (initial phase, days 1–3) to the biofilm matrix was followed by the development of the filamentous chlorophytes, Cladophora glomerata and Oedogonium spp. (intermediate phase, days 6–15) and then by stalk-forming diatoms particularly Gomphonema spp. (late phase, days 18–33). According to the redundancy analyses, water temperature and oscillations of Danube water level that define the flooding pattern had the most significant influence on algal colonization. Flood-induced spreading of metaphyton firstly supported the rapid progress of algal colonization towards a climax community, while later, metaphyton together with macrophytes disrupted algal community by increasing the mechanical injuries, shading and grazing pressure. Consequently, algal abundance and community structure were returned to the intermediate phase of colonization.

Spaniophlebia male genitalia is described for the first time and the diagnosis of the genus is improved in order to encompass this new set of characteristics. Spaniophlebia kayapo sp. nov. is described based on male and female imagos from Pará and Mato Grosso states, Brazil, Spaniophlebia trailiae is redescribed based on newly collected material and comparison with the types, and Spaniophlebia escomeli is transferred to the genus Lachlania based on wing features and distributional data. A key to male imagos of the genus is provided as well as considerations regarding type-localities of Spaniophlebia species.

This study first reports concentrations of arsenic (As) and selenium (Se) in fish tissue of Clarias gariepinus from Sagua la Grande River in the Villa Clara Province, Cuba. We also confirm the mercury (Hg) levels in these fish obtained previously. Individuals were captured in three areas near Sagua la Grande City, where this fish is a common source of food for the city inhabitants. Concentrations range of As, Hg and Se (in wet weight) were 0.01–0.11 μg.g−1; 0.03–0.24 μg.g−1 and 0.75–3.87 μg.g−1, respectively. As and Se levels were positively correlated (n=19, ρ=0.673, P<0.05). High levels of Se were found in fish tissue and in 31.6% (n=6) of individuals captured exceeded the threshold value for Se toxicity, which means that Se is likely to produce adverse consequences on the fish themselves or on the wildlife organisms that eat them. As and Se concentrations were positively correlated with fish weight and length (P<0.05). Fish from irrigation canal have higher Se concentrations than fish captured in the other two stations. However, no significant differences were found between Hg and As concentrations in fish at the three sampling stations. Finally, as the Se concentrations in C. gariepinus were abnormally high, we suggest the need for studies about Se sources in the zone, the effect of Se in fish and the intake associated with fish consumption.

Surface runoff can supply lakes with a variety of chemical substances – their type and quantity may significantly vary and depend on the characteristics of the catchment area: geomorphology, phytocoenosis type and degree of human impact. In this study we investigated the physicochemical properties of the surface runoff water collected from the wooded catchment of Lake Piaseczno Duze (LPD, Drawa National Park, Poland) covered by a monoculture of Scots pine (Pinus sylvestris) and mixed forest with white birch (Betula pubescens) as the dominant tree. Experimentally, we also aimed to study the leaching of nutrients from pine and birch litter. Throughout the investigated period runoff waters had low pH, brown colour and high levels of dissolved organic carbon (DOC) – most likely induced by humic acids. Furthermore, considerable levels of nitrogen (N) and phosphorus (P) were found. The highest concentrations of nutrients were observed in runoff collected after heavy rainfall and snow melting. Runoff from the coniferous area contained significantly higher levels of DOC but lower concentrations of N and P compared to runoff collected from the birch-dominated forest. Similar physicochemical conditions were observed in the leaching experiment. Moreover, it was found that the release of chemical substances from both coniferous and deciduous litter was rapid. Our study indicates that surface runoff from forest areas can significantly affect lake chemistry. Based on the simultaneous analyses of littoral water chemistry we suggest that it may contribute to LPD dystrophication through the transportation of high levels of acidic compounds.

We investigated the diel vertical distribution patterns of microcrustacean zooplankton (Cladocera, Copepoda) in a shallow pond (max. depth: 70 cm) of the Öreg-turján peatland (Ócsa, Central Hungary) during three 24-h periods in July (19–20th), August (17–18th) and September (11–12th) 2011. Environmental variables showed remarkable vertical stratification. Oxygen concentration was close to zero in the entire water column from night until sunrise, while the lower strata (from 20 cm below the surface) were close to anoxic during all three diel cycles. It proved to be the main determinant of the vertical distribution of microcrustaceans. Accordingly, the highest proportion of individuals was present in the surface layer. Chlorophyll-a concentration and phytoplankton biomass were inversely distributed compared to zooplankton. Microcrustaceans (mainly Daphnia curvirostris) migrated to the middle layer only in August, which could be explained by a trade-off between food resources, dissolved oxygen (DO) and competition with littoral zooplankters. The diurnal density patterns of microcrustaceans suggested horizontal migration into the aquatic macrophytes during night, which could be a strategy to avoid Chaoborus predation. Our results show that strong vertical gradients of abiotic and biotic factors occur even in such shallow waterbodies. Among them, DO can maintain constant vertical aggregation of zooplankters by limiting their occurrence to the surface layers.

Community diversity is expected to reflect variations in local conditions but, recently, ecologists have started to realize that local diversity is also under pressure from global processes. As a result, the traditional view of community structure based on local interspecific interactions was replaced by the idea that community structure is a result of multiple processes acting in different spatial scales. This study is aimed at quantifying the relative importance of spatial, environmental and spatially structured processes on Ephemeroptera community in Cerrado streams in Brazil. Thirty-four rivers and streams in the Brazilian state Mato Grosso were sampled. Ephemeroptera species composition, based on abundance and presence data, was evaluated in relation to niche and neutral predictors by using a partial redundancy analysis (pRDA). Results obtained through the pRDA indicated that both environmental and spatial processes influenced Ephemeroptera abundance. On the other hand, only environmental processes showed effects on community patterns when using species presence data from preserved, altered and large streams and also when looking only at the preserved sites. When streams larger than 20 m were excluded from analysis, both environmental and spatially processes showed influence on Ephemeroptera composition. Adjusted R2 values were higher for environmental than for spatial processes in all analyses. The relatively high influence of both environmental processes and stream width in the analyses highlights the sensitivity of mayflies assemblies to environmental variation, and emphasizes the importance of local processes, as predicted by niche theory, while neutral processes act to a lesser extent on the structure of the studied communities.

Macroinvertebrates have been collected in Flanders since 1989 by the Flemish Environment Agency to assess ecological water quality. During the present study, the collected waterbugs were identified to species level. In total, more than 90 000 waterbugs were identified, belonging to 45 species. Two of these are recent additions to Flemish fauna: Sigara iactans was found to be a common species in 1989, the first year of monitoring, which is earlier than the first records reported so far, whereas Cymatia rogenhoferi remains a very rare species. Five different communities could be recognized: (1) species occurring in alkaline waters with a high pH, (2) species occurring in colder waters that can tolerate slightly brackish and nutrient rich water, (3) species from running waters, (4) species from acidic waters and (5) ubiquist species that occurred in all types of water. Owing to the general improvement of chemical water quality during the last decade, most species increased, however, three pollution tolerant species declined significantly: Callicorixa praeusta, Corixa punctata and Sigara striata.

The present study focus on some aspects of zooplankton structure in the Alcantara River (Sicily, Italy), in relation to environmental factors. Zooplankton samplings were performed in spring in four sites, located from up- to downstream along the river course. Four low-flow velocity station points were chosen along a transversal river section in each site. Samples were taken from all station points in the four sites by two different mesh sizes (55 and 100 μm) rectangular nets. Rotifer abundances were an order of magnitude higher in 55 μm mesh size samples than in 100 μm mesh size ones. The two communities also resulted significantly different (ANOSIM test, ρ=0.212; P=0.1%). Generally, low abundances (from 3470±5133 to 422±474 ind.m−3) were explained by low chlorophyll a concentration and the high-flow regime of this river. Rotifer dominated the zooplankton community. Cladocerans, copepods and nauplii occurred with considerably lower abundances than rotifers. However, the relative contributions of these taxa to total abundances depended on the mesh sizes used. Euchlanis and Adineta genera exhibited the highest abundances in the rotifer assemblage. Conductivity alone or in association with temperature and dissolved oxygen was the most important environmental factor affecting rotifer community distribution. Cephalodella sp., Lepadella sp. and Trichotria pocillum showed a high positive relation to pico-plankton, showing this fraction as a possible rotifer food item. This paper demonstrated a higher efficiency of the finest net to characterize riverine zooplankton community that increases from up to downstream in terms of abundances and diversity.

Fish assemblages inhabiting the mountain streams of the Guiana shield have scarcely been studied. Here we investigated fish assemblages in eight headwater mountain streams of the Mount Itoupé (French Guiana), and tested how local freshwater fish assemblages are shaped by environmental characteristics. We show that Mount Itoupé streams host uneven species assemblages, characterized by low species richness (less than ten species per site) and a high proportion of small Siluriform species. Differences in fish assemblage composition between the sites were mainly due to basin identity, but regional climate and position of the site in the river gradient also had a significant effect, although of lower magnitude. In contrast, local habitat hardly affected fish richness, abundances or assemblage composition. Species richness increased along the upstream–downstream gradient, whereas fish abundance depended mainly on the slope orientation of Mount Itoupé. Although these results need confirmation on a larger amount of sampling sites, located on other Guianese mountains, this preliminary study shows that the mountain streams of the Guiana Shield, although rarely investigated, host not only uneven species assemblages, but also present an original combination of environmental determinants shaping fish assemblage structure. Those rare and original ecosystems hence deserve more attention and should be preserved from human disturbances.

Many adverse environmental factors influencing the Shatt-al Arab River, southern Iraq, during the past century and especially in recent years, combined with the ever-increasing demand for freshwater in the region, indicate the need to obtain information about its salinity regime. The aim of our study was both to find out what historical data there are and then to compare these with the results of a survey of the salinity and water quality of a stretch of the present river over the year October 2009–September 2010. The evidence suggests that there has been a marked upstream shift in the influence of sea water. Salinity values of 2 and 8‰ were found at two sites where elevated salinity had never been reported previously. Water quality variables indicated increased concentrations over the previous four decades and were beyond the national and international standards. As such changes in a major water resource have serious implications for the inhabitants of Basrah, the biological diversity in the river and the whole Gulf ecosystem, it is suggested that there should be a much more detailed study to provide the evidence needed to convince upstream water users of the need to conserve water and manage the whole catchment properly.