Zooplankton dynamics of two alkaline-saline lakes in the Keyan Rift Valley

Grundlegende Einflüsse auf die Dynamiken des Mesozooplanktons seichter saliner Seen waren bislang weitgehend unbekannt, obwohl solche Planktongemeinschaften die Fähigkeit besitzen Blüten mit außergewöhnlich hohen Dichten und Biomasse auszubilden. In unserer Studie haben wir daher die basalen Umwelt und ressourcenbassierenden biologischen Faktoren untersucht, um die charakteristischen Muster solcher Blüten, die hauptsächlich von brachioniden Rotatorien und von großen, omnivoren Ciliaten gebildet werden, darzulegen.Underling influences on mesozooplankton dynamics of shallow, saline lakes have widely been undiscovered in spite of the ability of such communities to form blooms of exceptional high density and biomass. In our study we investigated environmental and resource based biotic factors to disclose fundamental patterns of such blooms, which are mainly formed of branchionid rotifers and large omnivorous ciliates

A community-based evaluation of population growth and agro-pastoralist resilience in Sub-Saharan drylands

Human population growth is considered together with climate warming as major driver of change in Sub-Saharan Africa. Research on the implications of increased population densities often utilises community knowledge but without incorporating the view of local stakeholders. In this study, we applied a community-centred approach to assess direct and indirect consequences of population growth in drylands of north-western Kenya. Combined social, agricultural and geo-spatial analyses allowed us to identify major system transitions, determine their linkage to population growth and deduce consequences for local livelihoods and community resilience.Community-members reported positive and negative consequences of fourfold population growth since 1974 but evaluated its overall effect as clearly beneficial. This overall positive effect was based on both, positive developments and the successful mitigation of potential system stressors. First, food security was maintained despite high growth rates because a shift from migratory pastoralism to a more labour-intensive agro-pastoralist system helped to increase agricultural productivity. Additionally, land-use changes were linked to land privatisation and improved erosion protection on private land, decoupling population growth from environmental degradation.We detected, however also early warning signs of reduced community resilience as households were unable to fully recover livestock densities after catastrophic events. A population-growth driven reduction in household land-sizes and the decreased monetary value of agricultural production were identified as drivers of this development. The extrapolation of our results to establish a general relationship between population densities, land-use and household resilience in Sub-Saharan drylands suggest that further system transformations will be required to ensure regional food-security.Swedish Research Counci

First detection of a highly invasive freshwater amphipod (Crangonyx floridanus) in the United Kingdom

The freshwater gammarid, Crangonyx floridanus, originates from North America but has invaded and subsequently spread rapidly throughout Japan. We provide here the first genetic and microscopic evidence that C. floridanus has now also reached the United Kingdom. We found this species in two locations separated by more than 200 km (Lake Windermere in the North of the UK and Smestow Brook, West Midlands). The current distribution of C. floridanus is currently unknown, however, both sites are well connected to other river and canal systems. Therefore, the chance of further spread is high. Genetic analyses of C. floridanus indicate that British inland waters are colonised by the same lineage, which invaded Japan. We recommend further work to assess the distribution of this species and its impact on the local fauna and flora

Improving the reliability of eDNA data interpretation

Global declines in biodiversity highlight the need to effectively monitor the density and distribution of threatened species. In recent years, molecular survey methods detecting DNA released by target‐species into their environment (eDNA) have been rapidly on the rise. Despite providing new, cost‐effective tools for conservation, eDNA‐based methods are prone to errors. Best field and laboratory practices can mitigate some, but the risks of errors cannot be eliminated and need to be accounted for. Here, we synthesize recent advances in data processing tools that increase the reliability of interpretations drawn from eDNA data. We review advances in occupancy models to consider spatial data‐structures and simultaneously assess rates of false positive and negative results. Further, we introduce process‐based models and the integration of metabarcoding data as complementing approaches to increase the reliability of target‐species assessments. These tools will be most effective when capitalizing on multi‐source data sets collating eDNA with classical survey and citizen‐science approaches, paving the way for more robust decision‐making processes in conservation planning.GCR

The potential of fatty acid isotopes to trace trophic transfer in aquatic food-webs

Compound-specific isotope analyses (CSIA) of fatty acids (FA) constitute a promising tool for tracing energy flows in food-webs. However, past applications of FA-specific carbon isotope analyses have been restricted to a relatively coarse food-source separation and mainly quantified dietary contributions from different habitats. Our aim was to evaluate the potential of FA-CSIA to provide high-resolution data on within-system energy flows using algae and zooplankton as model organisms. First, we investigated the power of FA-CSIA to distinguish among four different algae groups, namely cyanobacteria, chlorophytes, haptophytes and diatoms. We found substantial within-group variation but also demonstrated that δ13C of several FA (e.g. 18:3ω3 or 18:4ω3) differed among taxa, resulting in group-specific isotopic fingerprints. Second, we assessed changes in FA isotope ratios with trophic transfer. Isotope fractionation was highly variable in daphnids and rotifers exposed to different food sources. Only δ13C of nutritionally valuable poly-unsaturated FA remained relatively constant, highlighting their potential as dietary tracers. The variability in fractionation was partly driven by the identity of food sources. Such systematic effects likely reflect the impact of dietary quality on consumers' metabolism and suggest that FA isotopes could be useful nutritional indicators in the field. Overall, our results reveal that the variability of FA isotope ratios provides a substantial challenge, but that FA-CSIA nevertheless have several promising applications in food-web ecology. This article is part of the theme issue ‘The next horizons for lipids as ‘trophic biomarkers’: evidence and significance of consumer modification of dietary fatty acids’.Svenska Forskningsrådet Forma

Integration of SWMM into a Dam Break, Hurricane, and Extreme Flood Modeling and Damage Assessment Framework

SWMM5 has been seamlessly integrated with a Geographic Information System (GIS) for simulation of inundation and analysis of consequences resulting from extreme flood events. The GIS-based environment processes digital elevation models, land use/cover data, stream networks and soils to create stream network, sub-basins, and cross-section shapefiles for river basins selected for analysis. The following readily-available public-domain datasets are utilized: 30-m topographical data from the United States Geological Survey (USGS), 30-m NLCD, Natural Resources Conservation Service (NRCS) (STATSGO), and National Hydrography Dataset (NHD). Rainfall predictions are made by a numerical weather model and ingested in gridded format into the simulation environment. Runoff hydrographs are estimated using Green-Ampt infiltration excess runoff prediction and a onedimensional diffusive wave overland flow routing approach. The hydrographs and the channel morphology are used to generate a SWMM5 compatibl