Beschrijving zandbalans Westerschelde en monding

Voor de beheerder van het Schelde estuarium, Rijkswaterstaat directie Zeeland, is het belangrijk om het bagger- en stortbeleid en het zandwinbeleid zo optimaal mogelijk in te richten. Hiertoe is inzicht in de zandhuishouding in zowel de Westerschelde als de monding gewenst. Een instrument om dat inzicht te verkrijgen is een historische zandbalans. In dit rapport wordt voor de Westerschelde en de monding (zowel het Nederlandse deel als het Belgische deel) de interne zandhuishouding opgesteld. Hieruit wordt vervolgens de zandbalans opgesteld, waarbij de \u91natuurlijke\u92 zanduitwisselingen tussen verschillende gebieden wordt bepaald, rekening houdend met de ingrepen (baggeren, storten en zandwinning) van de mens. Met de zandbalans is de import of export van zand van de Westerschelde en de monding bepaald. Daarnaast zijn ook de invloed van zeespiegelstijging en de 18,6 jarige cyclus in het getij, de zogenaamde autonome ontwikkelingen, onderzocht. Gezien het belang van de uitkomsten van de studie voor het toekomstige beleid is tenslotte ook de invloed van onzekerheden in de gebruikte gegevens en in de gebruikte aannames op de die uitkomsten bepaald. De studie toont aan dat de Westerschelde eind jaren \u9280 van de vorige eeuw omgeslagen is van een zandimporterend naar een zandexporterend systeem. Ook de monding is vanaf die periode exporterend, echter hebben onzekerheden in de gegevens in het Belgische deel van de monding kwantitatief invloed op deze conclusie. Daarnaast wijst de zandbalans sinds 1997 op een toenemende zandexport vanuit de Westerschelde en een toename van het sedimenttransport van het westelijke naar het oostelijke deel van de Westerschelde. De autonome ontwikkelingen hebben geen aantoonbare invloed op de zandhuishouding in de Westerschelde: uit de lineaire trend kan geen duidelijke invloed op de zandbalans worden vastgesteld. Door middel van statistische analyse (bepaling van de correlatie) is geen significante relatie gebleken tussen de 18,6 jarige cyclus in het getij en de gemeten volumeveranderingen. De invloed van onzekerheden van gegevens en aannames op de uitkomsten van de zandbalans zijn weliswaar aanwezig, maar brengen geen verandering in het beeld dat de Westerschelde exporterend is. Wel verschuift het moment waarop de omslag van import naar export optreedt. Het rapport besluit met een aantal praktische aanbevelingen voor het verbeteren van de zandbalansen die in de volgende jaren gemaakt zullen worden. De meeste aanbevelingen hebben betrekking op het verbeteren van de betrouwbaarheid en beschikbaarheid van (historische en toekomstige) gegevens in het Belgische deel van de monding

Optimization and validation of multi-coloured capillary electrophoresis for genotyping of Plasmodium falciparum merozoite surface proteins (msp1 and 2)

BACKGROUND: Genotyping of Plasmodium falciparum based on PCR amplification of the polymorphic genes encoding the merozoite surface proteins 1 and 2 (msp1 and msp2) is well established in the field of malaria research to determine the number and types of concurrent clones in an infection. Genotyping is regarded essential in anti-malarial drug trials to define treatment outcome, by distinguishing recrudescent parasites from new infections. Because of the limitations in specificity and resolution of gel electrophoresis used for fragment analysis in most genotyping assays it became necessary to improve the methodology. An alternative technique for fragment analysis is capillary electrophoresis (CE) performed using automated DNA sequencers. Here, one of the most widely-used protocols for genotyping of P. falciparum msp1 and msp2 has been adapted to the CE technique. The protocol and optimization process as well as the potentials and limitations of the technique in molecular epidemiology studies and anti-malarial drug trials are reported. METHODS: The original genotyping assay was adapted by fluorescent labeling of the msp1 and msp2 allelic type specific primers in the nested PCR and analysis of the final PCR products in a DNA sequencer. A substantial optimization of the fluorescent assay was performed. The CE method was validated using known mixtures of laboratory lines and field samples from Ghana and Tanzania, and compared to the original PCR assay with gel electrophoresis. RESULTS: The CE-based method showed high precision and reproducibility in determining fragment size (< 1 bp). More genotypes were detected in mixtures of laboratory lines and blood samples from malaria infected children, compared to gel electrophoresis. The capacity to distinguish recrudescent parasites from new infections in an anti-malarial drug trial was similar by both methods, resulting in the same outcome classification, however with more precise determination by CE. CONCLUSION: The improved resolution and reproducibility of CE in fragment sizing allows for comparison of alleles between separate runs and determination of allele frequencies in a population. The more detailed characterization of individual msp1 and msp2 genotypes may contribute to improved assessments in anti-malarial drug trials and to a further understanding of the molecular epidemiology of these polymorphic P. falciparum antigens

Genome Fragmentation Is Not Confined to the Peridinin Plastid in Dinoflagellates

When plastids are transferred between eukaryote lineages through series of endosymbiosis, their environment changes dramatically. Comparison of dinoflagellate plastids that originated from different algal groups has revealed convergent evolution, suggesting that the host environment mainly influences the evolution of the newly acquired organelle. Recently the genome from the anomalously pigmented dinoflagellate Karlodinium veneficum plastid was uncovered as a conventional chromosome. To determine if this haptophyte-derived plastid contains additional chromosomal fragments that resemble the mini-circles of the peridin-containing plastids, we have investigated its genome by in-depth sequencing using 454 pyrosequencing technology, PCR and clone library analysis. Sequence analyses show several genes with significantly higher copy numbers than present in the chromosome. These genes are most likely extrachromosomal fragments, and the ones with highest copy numbers include genes encoding the chaperone DnaK(Hsp70), the rubisco large subunit (rbcL), and two tRNAs (trnE and trnM). In addition, some photosystem genes such as psaB, psaA, psbB and psbD are overrepresented. Most of the dnaK and rbcL sequences are found as shortened or fragmented gene sequences, typically missing the 3′-terminal portion. Both dnaK and rbcL are associated with a common sequence element consisting of about 120 bp of highly conserved AT-rich sequence followed by a trnE gene, possibly serving as a control region. Decatenation assays and Southern blot analysis indicate that the extrachromosomal plastid sequences do not have the same organization or lengths as the minicircles of the peridinin dinoflagellates. The fragmentation of the haptophyte-derived plastid genome K. veneficum suggests that it is likely a sign of a host-driven process shaping the plastid genomes of dinoflagellates

Seasonal variations of suspended sediment and diatoms in the Western Scheldt

This study focused on the possible relationship between seasonal variations of suspended sediment concentration (SSC) and diatom biomass. In order to determine whether a relationship exists, the effect of other parameters on these seasonal variations was also studied. This was accomplished to prevent the risk of finding a spurious relationship between SSC and diatom biomass. This approach resulted in a literature study and the analysis of data. The literature study was necessary to provide the theoretical background, the data analysis was used for the quantification of the identified relationships. The literature survey showed that SSC variations do not affect diatom biomass in the Western Scheldt. Turbidity, caused by both SSC and organic matter, is too high throughout the year for diatoms to be active during inundation of the flats. Diatom, which are in fact algae, depend on the availability of light for their growth. The role of diatoms on SSC variations is an indirect one. Diatoms do not influence deposition of sediment, but they do play a role in stabilising fresh deposits. When this occurs on a large scale during a period of time, then suspended particles are constantly removed from the water column. A relation scheme was proposed in which all identified parameters and their relationships were summarised. Among the parameters that play a role in the seasonal variation of SSC and diatom biomass are wind, rain, discharge and biological activity. The flats play a role through seasonal changes in accretion and erosion of fine grained sediment. The interaction between SSC and diatoms takes place at the flats. Data acquisition and analysis was used to investigate the contribution of the various parameters to SSC and diatom biomass variations. It showed that wind is an important parameter, probably through the influence on hydrodynamic conditions. This was a result of the analysis of both short term, high frequency measurements and long term, low frequency measurements. The performed regression analyses explained only part of the SSC and diatom biomass variations. This indicates that the parameters on which no information was selected play a role. Also the fact that the analyses were performed on the scale of the entire estuary might contribute. Some indications for this assumption were provided in the analysis of spatial variations of SSC, discharge and chlorophyll a. Future research should aim at combining spatial and temporal scales and the use of other types of data and analysis techniques.Civil Engineering and Geoscience