Water-Quality Surveillance of Swiss Rivers

Water-quality surveillance is essential for the detection of anthropogenic impacts on rivers. The surveillance strategy designed by the EAWAG combines long-term, continuous monitoring necessary for assessing the success of measures implemented to fight pollution with short, intensive field and laboratory studies to elucidate element transformations and transport processes.Emphasis is put on sound methods of sampling and sample processing which are paramount for a clear interpretation of river quality data. Results from process-oriented case studies show how a combination of different methods of sampling and analysis brought new insights into phosphorus transport pathways and on the availability of particle-bound phosphate for phytoplankton

Longitudinal vegetation turnover in an eastern Rift Valley riparian corridor

AbstractEast African riparian corridors are biodiversity hot spots that occur in catchments degrading under deforestation and overgrazing. Quadrats and belt transects were employed to investigate plant succession along the River Gilgil, in the Kenyan Rift Valley. The study found that most species (total 365) were broadly distributed across the tropics, but Rift Valley endemics were 12.5%, and 4%–18% were exotic. Plant composition varied with altitude, lithology, soils and rainfall. Agglomerative (Jaccard) hierarchical clustering and Non‐metric Dimensional Scaling identified two and three vegetation groups, for quadrats and transects, respectively, correlated with lithology and soils. Indicator species analysis highlighted that the upstream portion of the catchment was characterised by forest taxa with few exotics. The downstream included woodland species adapted to mesic/xeric conditions and to overgrazing. Longitudinal change in species composition (β diversity) between sites was assessed by taking into consideration the contribution of 'spatial species turnover' and 'nestedness', resulting from species replacement and species loss, respectively. The β diversity of the riparian corridor vegetation was 0.40 and spatial turnover accounted for 80%–85% of this, while the rest was attributed to the nestedness component. Riverine and native trees increased downstream but with low regeneration. Afromontane vegetation extended its distribution towards lower altitudes

Brought more than twice: the complex introduction history of the red swamp crayfish into Europe

One of the biggest challenges in understanding and managing biological invasions is the identification of the routes of introduction. This information is often incomplete because of unnoticed, unreported and, sometimes, illegal translocations. Reports on the introduction of the red swamp crayfish (Procambarus clarkii) into Europe describe that it was introduced for the first time to southern Spain (1973 and 1974) from Louisiana; from there, it rapidly spread throughout several European countries. While other importation events and pathways of introduction have been suggested in the literature, there is no evidence that these led to wild populations in Europe. Our present study suggests two additional introduction routes into Europe from non-European areas where the red swamp crayfish had previously been reported. By using mtDNA, we found a shared haplotype between the Lake Naivasha in Kenya and Western Europe, as well as another between either western United States or Asia, and Malta. These findings support historical reports found in the literature for the former case and also point towards pet trade as driver of new introductions for the latter, thus highlighting the complex introduction history of the red swamp crayfish populations in Europe.Andalusian Government [RNM-936]PICS [PIC2015FR4, PICS07360

Structure and diversity of fish communities in man-made ponds of the Niger Delta (southern Nigeria)

1. A survey of eight local earthen hand-dug ponds located within the freshwater swamps of a Niger Delta area (southern Nigeria) was conducted over a period of 3 months. A total of 4,313 fishes representing 19 species from 12 families were recorded.2. The most abundant species was Xenomystus nigri (905 individuals), whereas the least common was Protopterus annectens (13). Cichlidae and Clariidae counted three species each, whereas Anabantidae, Hepsetidae, Mochokidae, Protopteridae, Phractolaemidae, Malapteruridae and Gymnarchidae were represented by a single species each.3. A lotic species, Synodontis sp., was recorded possibly as a result of the episodic flood of 2012.4. The Engenni swamps harbour a moderately diverse ichthyofauna. Regulations should be put in place to further enhance the fisheries potential of these local ponds

Dissolved organic matter in continental hydro-geothermal systems: insights from two hot springs of the East African Rift valley

Little is known about the quantity and quality of dissolved organic matter (DOM) in waters from continental geothermal systems, with only a few reports available from the Yellowstone US National Park. In this study, we explored the chemodiversity of DOM in water samples collected from two geothermal hot springs from the Kenyan East African Rift Valley, a region extremely rich in fumaroles, geysers, and spouting springs, located in close proximity to volcanic lakes. The DOM characterization included in-depth assessments performed by negative electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Reduced, saturated and little aromatic DOM compounds were dominant in the hot spring waters collected from either the Ol Njorowa gorge (ON) or the south shore of the soda-saline Lake Elementaita (ELM). Oxygen-poor and sulfur-bearing DOM molecules prevailed in ON, probably reflecting abiotic sulfurization from sulfide-rich geofluids. Nitrogen-bearing aliphatic and protein-like molecules were abundant in ELM, possibly perfusing through the organic-rich sediments of the adjacent Lake Elementaita. Notably, the heat-altered DOM of ancient autochthonous derivation could represent an overlooked source of aliphatic organic carbon for connected lentic environments, with a potential direct impact on nutrient cycling in lakes that receive geothermal water inputs

Trophic resource use by sympatric vs. allopatric Pelomedusid turtles in West African forest waterbodies

Organisms that are similar in size, morphological characteristics, and adaptations, including vertebrates, often coexist by partitioning the available resources (food, space, and time). So, studies of the dynamics of these cases of coexistence are scientifically interesting. Here, we study a coexistence case of two species of freshwater turtles inhabiting the forest waterbodies of West Africa, focusing on the dietary habits of the two species. We found that both turtle species are omnivorous generalists, eating both vegetal and animal matter abundantly. However, there were clear interspecific differences, with the larger of the two species (P. cupulatta) eating more vertebrates (mainly fish but occasionally other vertebrates), whereas P. castaneus consumed more invertebrates. These patterns appeared consistently within the species and across sites, highlighting that the same patterns were likely in other conspecific populations from the Upper Guinean forest streams (Côte d’Ivoire and Liberia). Our study also showed that interspecific competition for food does not occur between these two species; instead, previous studies uncovered that a clear partitioning of the habitat niche occurs. We conclude that the food resource is likely unlimited in the study areas, as it is not the case in more arid environments (since food shortages may occur during the dry season). We anticipate that, within the Pelomedusidae communities throughout Africa, intense competition for food probably occurs in the Sahel and Sudanian vegetation zones, particularly during the dry months, but is unlikely within the Guinea and wet savannah region and even less likely in the Guineo-Congolian rainforest region

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

Long-term population dynamics in a Mediterranean aquatic snake

A review of several long-term studies has recently suggested that snakes might be declining in large parts of the world. Additional data from other long-term studies are therefore urgently needed in order to assess the generalities of such suggested declines. Based on a 20-year study, we analyzed demographic data on adult dice snakes (Natrix tessellata) studied in central Italy between 1985 and 2004. Both male and female dice snakes were relatively long-lived, with no significant differences in longevity between the sexes. Individual males and females were observed over a maximum of 10 and 14 years, respectively. However, the among-year recapture rates between the year the snakes were initially captured and the subsequent year (i. e., year 1 to year 2) was significantly lower (45%) than the among-year recapture rates during subsequent years (74%; i. e., year 2 to year 3), suggesting that a large proportion of the snakes at first capture were in fact not resident within our study area, and hence many snakes were migrating in and out of our 2-km stream study site, with no inter-sexual difference in dispersal rates. Sex ratio was virtually equal if we consider the study period as a whole. Significant annual fluctuations were, however, observed through the study. In 1985-1990, 1993-1995, 1998 and 1999 the sex ratio was male-biased, whereas in 2000-2004 female-biased. In terms of both survival and recapture probabilities, model selection showed that Akaike\u27s information criterion favored the model incorporating body size, with the model incorporating year having an intermediate likelihood, and the model with sex included being the most disfavored. Total population number estimates suggest an average 86 adult individuals along the 2 km of stream with only minor annual variations. However, a significant decrease in the number of males occurred during the last 6 years of our study. Thus, further monitoring of this population is warranted in light of the decline of snake populations reported recently

FISH COMMUNITY COMPOSITION INDICATES LOW IMPACT OF CAPTURE EFFORTS IN WAR-TORN SOUTH SUDAN

A survey conducted in Terekeka, Mongalla (=Mongalla) and Gemmaiza (= Gemeiza), payams of Central Equatoria in South Sudan using face-to-face interviews, structured questionnaire and focused group discussion provided information on income generating strategies of fishing communities. These included: full time or part time fishing, small-scale farming, cattle breeding and firewood collection. Stationary gill nets were the dominant type of fishing gear, followed by  monofilament, hook and long line, cast nets, spears and harpoons. Fishing vessels included planked canoes, steel boats and fibreglass. The best fishing months were August, September, followed by May. Main species caught included large bodied potamodromous predators adapted to channel habitats, as well as floodplain migrants. Overall the fish community appeared to be at equilibrium, with no evidence of impacts due to excessive catch efforts. The good health of the White Nile fishery is related to the high resilience of South Sudanese aquatic ecosystems as well as to the low potential of fish capture in a country disrupted by war and lack of security

A review of allodiversity in Lake Naivasha, Kenya:developing conservation actions to protect East African lakes from the negative impacts of alien species

The biodiversity of developing countries is increasingly threatened by introductions of invasive alien species. This study on the allodiversity in Lake Naivasha, Kenya reviews the pathways, establishment rates and outcomes of introduced species, and provides the basis for determining conservation actions that, if implemented, could prevent potentially harmful effects of similar events in other East African lakes. Introductions into Naivasha commenced in the 1920s with the release of a sport fish and have since produced an allodiversity of 23 species. This includes species that are no longer present (e.g., some tilapia species), presumed no longer present (e.g., the Nile perch Lates niloticus) or whose distribution is highly localised and ecologically neutral (e.g., the coypu Myocastor coypus). It also includes species that established successfully and invoked major changes in lake ecology (e.g., the red swamp crayfish Procambarus clarkii) and a species that is producing apparent economic benefits to the local population (i.e., the common carp Cyprinus carpio). The most frequent donor continents were the Americas and most species were the result of secondary introductions. The main introduction vector was active release that aimed to enhance fishery production. Alien species now dominate each main level of the lake’s food web and produce impacts that are rarely restricted to a single ecosystem service. With a few exceptions, the majority of introductions translate into socioeconomic costs that contribute to rising social conflicts and exacerbating poverty. Development of appropriate conservation management tools within a regulatory framework could help protect Naivasha from further damage and could be used elsewhere in East African lakes to ensure that subsequent introductions enhance ecosystem services without affecting biodiversity