River otter and mink occupancy dynamics in riparian systems

Semi-aquatic mammals are dependent upon streams and riparian areas, which are a product of the landscapes they drain. Both local stream morphology and surrounding land use are likely to have important influences on current occupancy of semi-aquatic mammals and potentially affect future geographic distributions. We identified aspects of the riparian system and stream structure at multiple scales that relate to the presence of river otter (Lontra canadensis) and mink (Neovison vison) to better understand how changing landscapes affect occupancy dynamics of these semi-aquatic mammals and to facilitate future monitoring and management. We estimated multi-season occupancy using 103 sites sampled over 6 seasonal sampling periods in southern Illinois, USA (44,526 km²) during 2012–2014. We hypothesized river otter and mink occupancy were related to multiple aspects of landscape and local habitat attributes including land cover, water availability, human disturbance, and stream characteristics. Occupancy of river otter was predicted by large stream size, less developed area near the stream site, and proximity to areas with reintroduced or remnant populations of river otter. Mink were more likely to occupy sites with small streams and decreased water availability near the site. However, top models for both species had low weights and high uncertainty for multiple variables. Habitat-based models may not be the best predictors of occupancy for these carnivores because they are more likely to respond to prey diversity or availability, but landscape changes that decrease natural water availability and increase human disturbance to the stream at the local scale are likely to negatively affect river otter. © 2019 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Interaction of sauger Sander canadensis and walleye Sander vitreus in a large,shallow northern river

The objectives of this study were to: (1) determine the relative abundance of sauger Sander canadensis and walleye S. vitreus within the Rainy River using a standardized index netting technique; (2) assess the life-history characteristics of the two species in a northern river; (3) examine the spatial distribution of the two species; (4) assess year-class synchrony. At a larger scale, relative abundance of S. canadensis and S. vitreus were similar among sections of the river. However, at a finer scale, S. canadensis were the dominant species over more area (24%) of the river than S. vitreus (12%). Life-history traits for both species were within the range reported for North American. Mortality rates were similar, suggesting that anglers were not affecting one species more than the other. Year-class strengths were not synchronous between S. canadensis and S. vitreus (r = 0.07). There was evidence of S. canadensis potentially outcompeting S. vitreus with a strong year class of S. canadensis followed by a very weak class of S. vitreus. Additionally, S. canadensis were larger than S. vitreus in most sections of the river when adjusted for mean size. However, the potential interspecific competition was not to the exclusion of S. vitreus. Turbidity was probably the factor that enable S. canadensis to survive sympatrically with S. vitreus given their inability to segregate by depth within the river.     

Can environmental flows moderate riparian invasions? The influence of seedling morphology and density on scour losses in experimental floods

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Lateral hydrological connectivity differentially affects the community characteristics of multiple groups of aquatic invertebrates in tropical wetland pans in South Africa

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A comprehensive examination of the network position hypothesis across multiple river metacommunities

The hierarchical branching nature of river networks can have a strong influence on the assembly of freshwater communities. This unique structure has spurred the development of the network position hypothesis (NPH), which states that the strength of different assembly processes depends on the community position in the river network. Specifically, it predicts that 1) headwater communities should be exclusively controlled by the local environment given that they are more isolated and environmentally heterogeneous relative to downstream reaches. In contrast, 2) downstream communities should be regulated by both environmental and dispersal processes due to increased connectivity given their central position in the riverscape. Although intuitive, the NPH has only been evaluated on a few catchments and it is not yet clear whether its predictions are generalizable. To fill this gap, we tested the NPH on river dwelling fishes using an extensive dataset from 28 French catchments. Stream and climatic variables were assembled to characterize environmental conditions and graph theory was applied on river networks to create spatial variables. We tested both predictions using variation partitioning analyses separately for headwater and downstream sites in each catchment. Only 10 catchments supported both predictions, 11 failed to support at least one of them, while in 7 the NPH was partially supported given that spatial variables were also significant for headwater communities. We then assembled a dataset at the catchment scale (e.g. topography, environmental heterogeneity, network connectivity) and applied a classification tree analysis (CTA) to determine which regional property could explain these results. The CTA showed that the NPH was not supported in catchments with high heterogeneity in connectivity among sites. In more homogeneously connected catchments, the NPH was only supported when headwaters were more environmentally heterogeneous than downstream sites. We conclude that the NPH is context dependent even for taxa dispersing exclusively within streams.     

Phytoplankton and Nutrients in the River Strymon,Greece

Phytoplankton species composition, biomass, diversity, nutrients and chlorophyll a were studied at monthly intervals from December 1991 to December 1992 in a selected area of the river Strymon. SRP ranged from 53 to 182 μg⁻¹ l⁻¹ and DIN from 265 to 850 μg⁻¹ I⁻¹. Nutrient values do not indicate strong anthropogenic effects. Chlorophyll α ranged from 1.0 to 35.3 μg⁻¹ I⁻¹ and followed the temporal distribution of total phytoplankton biomass. Phytoplankton biomass exhibited maxima in winter – spring and summer (6.8 g m⁻³ in December 1991, 4.8 g m⁻³ in April 1992 and 9.3 g m⁻³ in August 1992) composed mainly of diatoms, chlorphytes, cyanophytes and dinophytes. Nanoplankton was the most important component of phytoplankton biomass (69.5%) revealing increased values in winter and early spring. Phytoplankton diversity ranged from 0.8 to 3.2. The hydrological conditions in the river Strymon seem to be appropriate for the algae to reproduce themselves in the running water and so, to develop as a true potamoplankton. However, significant populations of phytoplankton must have been carried out from the Kerkini reservoir, situated at the north of the sampling station. The phytoplankton species composition and their periodicity in the river resemble those of typical, large, lowland and nutrient – rich rivers of Europe.     

Helicobacter pylori in Japanese river water and its prevalence in Japanese children

AIMS: The major transmission route of Helicobacter pylori remains unclear. In this study, we examined H. pylori in the environmental waters in Japan. METHODS AND RESULTS: A total of 24 water samples were collected from the upper, middle and downstream reaches of four Japanese rivers. Helicobacter pylori-specific DNA was examined using nested PCR. In addition, 224 children who lived near one river were studied by the stool antigen test for H. pylori prevalence. Helicobacter pylori DNA was detected in the water from the middle and downstream reaches of all four rivers, but not in the upper reaches. Helicobacter pylori was not found in cultured water samples with positive PCR results. Helicobacter pylori prevalence in the children examined was 9.8% for those living near the middle reaches and 23.8% nearby downstream, both of which were higher than the value in an area distant from the river (0%) (both, P < 0.01). CONCLUSIONS: Difference in H. pylori prevalence in the children may be related to the presence of H. pylori in the river. The results of this study showed that H. pylori DNA is frequently present in river water from the middle and downstream reaches in which the human biosphere is embedded. SIGNIFICANCE AND IMPACT OF THE STUDY: It is suggested that river water in the natural environment could be a risk factor for H. pylori transmission.     

Lignocellulolytic Enzyme Production by Aquatic Hyphomycetes Species Isolated from the Nile's Delta Region

Twenty-six species of aquatic hyphomycetes were isolated from woody sources (unidentified wood segments, leaf skeletons and neck of leaves and bark) in the North River Nile (Delta region). Alatospora acuminata, Anguillospora crassa, Flagellaspora penicillioides, Lunulospra curvula, Tetracladium marchalianum and Triscelophorus monosporus were the most common species. Temperature was the highest physico-chemical parameter affecting the aquatic hyphomycetes occurrence. Twelve species of hyphomycetes, isolated from woody substrates, were screened for their ability to produce extracellular lignocellulolytic enzymes on solid media. The enzymes tested included: endoglucanase, endoxylanase, beta-glucosidase, laccase, peroxidase, polyphenoloxidase, tyrosinase and beta-xylosidase. Three species, A. acuminata, F. penicillioides, T. monosporus, were positive for all tested enzymes. Also, A. longissima was positive for all enzymes except lignin-peroxidase. The ability to produce cellulase was 100% for all species while only, four species were positive for lignin-peroxidase. The ability of the species to produce other lignocellulotic enzyme ranged from 50% to 83%. Freshwater hyphomycetes have been shown to produce a rich array of enzymes able to degrade the polysaccharides of plant debris.