Fish zonations and guilds as the basis for assessment of ecological integrity of large rivers

Longitudinal zonation concepts describe the downstream changes in chemico-physical and biological properties of rivers. Including information on ecological fish guilds can enhance the usefulness of fish zonation concepts, in a way that they can be used as tools for assessment and management of the ecological integrity of large rivers. We present an ecological characterization of fish zones and fish communities in near-natural and in regulated large rivers in Europe (the River Doubs in France and the Rivers Rhine and Meuse in the Netherlands), using guild classifications of several life-history traits of fish and national Red Lists of threatened species. The Doubs data set was also analyzed using indices of the sensitivity of fish species to environmental degradation and indices for eurytopy. In these rivers, the number of ecological guilds per zone increases downstream, and there are clear shifts in the structure of the guilds. Flow preference and reproduction ecology of river fish are closely linked. The proportion of rheophilic species in the fish community decreases downstream, and the proportions of limnophilic and eurytopic species increase. Lithophilic and psammophilic spawners are dominant in the upper zones, whereas the lower zones are dominated by phytophilic and phytolithophilic spawners. The proportion of zoobenthivorous and periphytivorous species decreases downstream, and the proportion of zooplanktivorous and phytivorous species increases. However, because the European fish fauna mainly consists of feeding generalists, the discriminative abilities of simplistic feeding guild classifications are not very high. Guilds of sensitive, stenoecious species that share life history strategies that are highly adapted to specific riverine conditions (rheophils and limnophils) have declined far more than generalist species that can survive in a wide range of habitats that are not characteristic of natural river ecosystems. Because of the subsequent over-abundance of the eurytopic species the original longitudinal fish zonations are hardly recognizable anymore in heavily impacted large rivers such as the River Rhine. Hence these rivers do not meet the criteria for ecological integrity. Within a specific fish region, a suitable way of analyzing and monitoring the impact of human disturbance on the structure of the fish community is by comparing the guild structure of the present state of a fish zone with that of the reference situation.     

Prediction of plant species distribution in lowland river valleys in Belgium: modelling species response to site conditions

In ecological modelling, limitations in data and their applicability for predictive modelling are more rule than exception. Often modelling has to be performed on sub-optimal data, as explicit and controlled collection of (more) appropriate data would not be feasible. An example of predictive ecological modelling is given with application of generalized additive and generalized linear models fitted to presence–absence records of plant species and site condition data from four nutrient-poor Flemish lowland valleys. Standard regression procedures are used for modelling, although explanatory and response data do not meet all the assumptions implicit in these procedures. Data were non-randomly collected and are spatially autocorrelated; model residuals retain part of that correlation. The scale of most site-condition records does not match the scale of the response variable (species distribution). Hence, interpolated and up-scaled explanatory variables are used. Data are aggregated from distinct phytogeographical regions to allow for generalized models, applicable to a wider population of river valleys in the same region. Nevertheless, ecologically sound models are obtained, which predict well the distribution of most plant species for the Flemish river valleys considered.     

Vegetation composition of a threatened hypersaline lake (Lake Bardawil), North Sinai

Lake Bardawil is the only oligotrophic hypersaline lagoon along theMediterranean coast of Egypt. Its ecological significance is increasing due tothe progressive degradation of comparable wetlands in the region. The aim ofthis study is to analyse the structure and life forms of the vegetation alongthe lake before the execution of the North Sinai Agricultural DevelopmentProject (NSADP) which will threaten the ecosystem of the lake. A data set of150 stands was analysed using multivariate procedures(TWINSPAN, DCA and CCA), to classify the lake's vegetation, and to determinetherelationship between the plant community structure and the environmentalfactors. The classification and ordination resulted in a clear demonstration ofnine vegetation groups associated with four habitat types: submerged seagrasses, salt marshes and sabkhahs, eastern and middle calcareous dunes, andwestern non-calcareous dunes. The first axis of the CCA-ordination separatesthe salt marshes andsabkhahs species from those of the sand dunes along the soil salinity, watertable depth, cations, and pH gradients. CaCO₃ and soil textureshowedhighly significant correlation with the second axis of CCA which was animportant predictor for the psammophytic species distribution. The life formsranged from hydrophytes (sea grasses) to phanerophyteswith the dominance of therophytes and chamaephytes. Geophytes and chamaephytesdominate the saline habitats, while therophytes and hemicryptophytes dominatedthe sandy dunes. Eventhough the eastern section of the lake (Lake Zaraniq) wasdeclared as a RAMSAR site, Lake Bardawil needs urgent management to prevent itspollution by the new land use system.     

Influence of recirculation over COD and N-NH4 removals from landfill leachate by horizontal flow constructed treatment wetland

Abstract

Treatment of landfill leachate is a challenge due to its complex chemical composition and high recalcitrance and because of high costs for conventional wastewater treatment. In our study, leachate from the Quitaúna Landfill, Sao Paulo Metropolitan Region, Brazil, was treated at a laboratory scale with a horizontal subsurface flow constructed treatment wetland (HF-CTW) operating under a recirculation regime. Two units planted with Heliconia psittacorum (HP) and Cyperus papyrus (CP), and one unplanted control unit were assessed. With a recirculation regime over 21?days, the planted units removed 40% of chemical oxygen demand (COD) while the control unit removed only 29%. True color removal efficiencies were 2, 22, and 23% for the control, HP, and CP HF-CTWs, respectively. The ammonium nitrogen removal efficiencies for a 21-day hydraulic retention time (HRT) were 63–81% for planted units and 72% for the control. The increase of the HRT from 7 to 21?days led to the enhancement of ammonium nitrogen removal but did not affect the COD and total nitrogen removals. This phenomenon is a consequence of leachate’s low biodegradability. The present study shows the importance of the HRT and plant presence for landfill leachate treatment using HF-CTWs.     

A high-resolution map of the H1 locus harbouring resistance to the potato cyst nematode Globodera rostochiensis

The resistance gene H1 confers resistance to the potato cyst nematode Globodera rostochiensis and is located at the distal end of the long arm of chromosome V of potato. For marker enrichment of the H1 locus, a bulked segregant analysis (BSA) was carried out using 704 AFLP primer combinations. A second source of markers tightly linked to H1 is the ultra-high-density (UHD) genetic map of the potato cross SH × RH. This map has been produced with 387 AFLP primer combinations and consists of 10,365 AFLP markers in 1,118 bins (). Comparing these two methods revealed that BSA resulted in one marker/cM and the UHD map in four markers/cM in the H1 interval. Subsequently, a high-resolution genetic map of the H1 locus has been developed using a segregating F₁ SH × RH population consisting of 1,209 genotypes. Two PCR-based markers were designed at either side of the H1 gene to screen the 1,209 genotypes for recombination events. In the high-resolution genetic map, two of the four co-segregating AFLP markers could be separated from the H1 gene. Marker EM1 is located at a distance of 0.2 cM, and marker EM14 is located at a distance of 0.8 cM. The other two co-segregating markers CM1 (in coupling) and EM15 (in repulsion) could not be separated from the H1 gene.Communicated by J.G. Wenzel     

A set of modular plant transformation vectors allowing flexible insertion of up to six expression units

We have constructed a binary vector for Agrobacterium-mediated plant transformation, which has a multiple cloning site consisting of 13 hexanucleotide restriction sites, 6 octanucleotide restriction sites and 5 homing endonuclease sites. The homing endonuclease sites have the advantages to be extremely rare in natural sequences and to allow unidirectional cloning. We have also constructed a set of auxiliary vectors allowing the assembly of expression cassettes flanked by homing endonuclease sites. The expression cassettes assembled in these auxiliary vectors can be transferred into the binary vector with virtually no risk of cutting the vector within previously introduced sequences. This vector set is ideally suited for the construction of plant transformation vectors containing multiple expression cassettes and/or other elements such as matrix attachment regions. With this modular vector system, six different expression units were constructed in as many auxiliary vectors and assembled together in one plant transformation vector. The transgenic nature of Arabidopsis thaliana plants, transformed with this plant transformation vector, was assessed and the expression of each of the six genes was demonstrated.     

Anaerobic treatment of sulphate-rich wastewaters

Until recently, biological treatment of sulphate-rich wastewater was rather unpopular because of the production of H₂S under anaerobic conditions. Gaseous and dissolved sulphides cause physical-chemical (corrosion, odour, increased effluent chemical oxygen demand) or biological (toxicity) constraints, which may lead to process failure. Anaerobic treatment of sulphate-rich wastewater can nevertheless be applied successfully provided a proper treatment strategy is selected. The strategies currently available are discussed in relation to the aim of the treatment: i) removal of organic matter, ii) removal of sulphate or iii) removal of both. Also a whole spectrum of new biotechnological applications (removal of organic chemical oxygen demand, sulphur, nitrogen and heavy metals), recently developed based on a better insight in sulphur transformations, are discussed.     

Single-Molecule Imaging of the H-Ras Membrane-Anchor Reveals Domains in the Cytoplasmic Leaflet of the Cell Membrane

In the last decade evidence has accumulated that small domains of 50–700 nm in diameter are located in the exoplasmic leaflet of the plasma membrane. Most of these domains supposedly consist of specific sets of lipids and proteins, and are believed to coordinate signal transduction cascades. Whether similar domains are also present in the cytoplasmic leaflet of the plasma membrane is unclear so far. To investigate the presence of cytoplasmic leaflet domains, the H-Ras membrane-targeting sequence was fused to the C-terminus of the enhanced yellow fluorescent protein. Using single-molecule fluorescence microscopy, trajectories of individual molecules diffusing in the cytoplasmic leaflet of the plasma membrane were recorded. From these trajectories, the diffusion of individual membrane-anchored enhanced yellow fluorescent protein molecules was studied in live cells on timescales from 5 to 200 ms. The results show that the diffusion of 30–40% of the molecules is constrained in domains with a typical size of 200 nm. Neither breakdown of actin nor cholesterol extraction changed the domain characteristics significantly, indicating that the observed domains may not be related to the membrane domains identified so far.     

Linear pharmacokinetic parameters for monoclonal antibodies are similar within a species and across different pharmacological targets: A comparison between human,cynomolgus monkey and hFcRn Tg32 transgenic mouse using a population-modeling approach

The linear pharmacokinetics (PK) of therapeutic monoclonal antibodies (mAbs) can be considered a class property with values that are similar to endogenous IgG. Knowledge of these parameters across species could be used to avoid unnecessary in vivo PK studies and to enable early PK predictions and pharmacokinetic/pharmacodynamic (PK/PD) simulations. In this work, population-pharmacokinetic (popPK) modeling was used to determine a single set of ‘typical’ popPK parameters describing the linear PK of mAbs in human, cynomolgus monkey and transgenic mice expressing the human neonatal Fc receptor (hFcRn Tg32), using a rich dataset of 27 mAbs. Non-linear PK was excluded from the datasets and a 2-compartment model was applied to describe mAb disposition. Typical human popPK estimates compared well with data from comparator mAbs with linear PK in the clinic. Outliers with higher than typical clearance were found to have non-specific interactions in an affinity-capture self-interaction nanoparticle spectroscopy assay, offering a potential tool to screen out these mAbs at an early stage. Translational strategies were investigated for prediction of human linear PK of mAbs, including use of typical human popPK parameters and allometric exponents from cynomolgus monkey and Tg32 mouse. Each method gave good prediction of human PK with parameters predicted within 2-fold. These strategies offer alternative options to the use of cynomolgus monkeys for human PK predictions of linear mAbs, based on in silico methods (typical human popPK parameters) or using a rodent species (Tg32 mouse), and call into question the value of completing extensive in vivo preclinical PK to inform linear mAb PK.