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.

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.

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.

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.

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.

Banks of navigable canals are often stabilized with “hard” materials resulting in unsuitable conditions for marginal riparian vegetation. A constructed marginal shallow and sheltered water zone can favour riparian vegetation. In 1998, a new canal branch with shallow water zones was constructed along the canal Ghent-Bruges (Belgium). This study analysed plant vegetation development of these shallow zones, its spatial variation and its mid-way succession. For this purpose, riparian vegetation was investigated by plots in the middle of the shallow water zones, on the canal bank side and on the defence dam side in 2006 and 2009. The studied shallow water zones permitted the development of helophyte vegetation on the sides but hardly in the middle. Differences in number of taxa, diversity-index and Grime's competitiveness and ruderality were observed on the sides. The application of different construction materials is discussed as a possible cause. An increase of competitiveness and a decrease of ruderality indicated vegetation succession during the period 2006–2009. Rooted aquatic plant vegetation was poorly developed in the studied shallow water zones probably due to the deposition and accumulation of fine sediments. The results were interpreted in relation to possible design principles of shallow water zones and might be useful for waterway managers, policy-makers and technicians in future bank engineering projects along navigable canals. Moreover, the study contributes to the knowledge of mitigating negative ecological effects associated with navigation. Such bank rehabilitation measures may be necessary to achieve the ecological goals of the European Water Framework Directive.

The influence of the sediment grain size and the trophic status of the reservoirs on the composition, richness and biomass of Oligochaeta community was tested. Samples were taken from the littoral and profundal zones of 30 neotropical reservoirs from six different watersheds during two hydrological periods (dry and rainy seasons). The sample units were ordinated, with principal component analyses, according to differences in the sediment grain size, sample depth and dissolved oxygen. The results of a multiple response permutation procedure (MRPP) analysis revealed significant differences in species composition between littoral and profundal zones, trophic status (oligotrophic, mesotrophic and eutrophic) and different watersheds. The environment–species relationship was tested using redundancy analyses. In order to test which environmental variables, either granulometric or limnological, influenced the Oligochaeta community variability we used a partitioning procedure of inertia. Local variations, including reservoir zone and trophic status, were primarily influenced by differences in sediment type and depth. Significant differences in the total biomass between zones, trophic status, watershed and hydrological period were also demonstrated by a Kruskal–Wallis or Mann–Whitney test. The most prevalent taxa were the cosmopolitan tubificids Bothrioneurum sp. and Branchiura sowerbyi, and the naidids Dero (Dero) digitata and Pristina breviseta, which are dependent on periphyton for food. Higher biomass values were recorded in mesotrophic reservoirs, due to increased nutrient availability and adequate dissolved oxygen supply. Our results indicate that the Oligochaete community structure is directly influenced by local environmental variation in neotropical reservoirs; and that the sediment grain size is the most important factor in determining the Oligochaete community structure.

In China, although the production and use of organochlorine pesticides (OCPs) have been banned for decades, relatively high levels of OCP residues have still been found in some water bodies, and can result in adverse acute and chronic effects on zooplankton including rotifers, which have  caused public concern for many years. Responses in the population growth and reproduction of freshwater rotifer Brachionus calyciflorus to four OCPs including aldrin, dieldrin, β-hexachlorocyclohexane (β-HCH) and chlordecone were studied by 3-day population growth and 4-day resting eggs (RE) production tests. In comparison with control, aldrin at 10 μg.L−1, β-HCH at 1000 μg.L−1 and chlordecone at 0.05 μg.L−1 significantly increased the population growth rate (r); but aldrin at 100 μg.L−1, dieldrin at 0.001 and 0.1 μg.L−1, β-HCH at 0.1–100 μg.L−1 and chlordecone at 50 μg.L−1 markedly decreased it. Aldrin at concentrations higher than 1 μg.L−1, dieldrin at 0.01 and 1000 μg.L−1, β-HCH at concentrations 0.1 and higher than 1 μg.L−1, and chlordecone at concentrations 0.005 and higher than 0.5 μg.L−1 significantly decreased the ratio of ovigerous females to non-ovigerous females (OF/NOF), but the reverse was true for aldrin at 0.1 μg.L−1 and β-HCH at 0.001 μg.L−1. Dieldrin at 0.001, 0.01 and 1000 μg.L−1 significantly decreased the ratio of mictic females to amictic females (MF/AF), but β-HCH at 1 and 10 μg.L−1 highly significantly increased it. Dieldrin at 1000 μg.L−1 and β-HCH at concentrations higher than 10 μg.L−1 markedly decreased the fertilization rate (FR). Both aldrin and chlordecone have no significant effect on the MF/AF and FR of rotifers. Aldrin at concentrations higher than 1 μg.L−1, dieldrin at lower than 0.1 and higher than 10 μg.L−1, β-HCH at 1000 μg.L−1 and chlordecone at 0.005, 0.05 and 50.0 μg.L−1 significantly decreased the mictic rate (MR) of rotifers, but the reverse was true for β-HCH at 1 μg.L−1. Aldrin at 10 μg.L−1, dieldrin at 0.001, 0.1 and 1000 μg.L−1, β-HCH at concentrations higher than 1 μg.L−1 and chlordecone at concentrations higher than 0.005 μg.L−1 markedly decreased RE production of rotifers, but β-HCH at 0.01 μg.L−1 significantly increased it. A clear dose–response relationship existed between the RE and the concentration of dieldrin, β-HCH and chlordecone, and the OF/NOF and the aldrin concentration. The RE and OF/NOF in rotifer population might be suitable endpoints for monitoring the low concentration of three OCPs (dieldrin, β-HCH and chlordecone) and aldrin, respectively.