Trophic interactions between ciliates and nematodes from an intertidal flat

The present study investigated the possibility of a trophic link between ciliates and nematodes in fine sandy sediments of the Molenplaat intertidal flat (Schelde estuary, SW Netherlands). Grazing experiments were conducted under controlled laboratory conditions, with ciliate species isolated from enrichment cultures and nematodes collected directly from the field. Significant reductions in ciliate numbers were found in the presence of the predatory nematode Enoploides longispiculosus, a prominent species (and genus) in fine to medium sandy sediments of the North Sea and adjacent estuaries. No such effects were found when ciliates were inoculated with a mix of mainly deposit-feeding nematodes from the same sampling site. On the basis of these results, ciliate predation by E. longispiculosus was tested for several benthic ciliate species and abundances, at a range of predator abundances and temperatures, and in the presence of alternative prey (in casu nematodes). E. longispiculosus significantly reduced the densities of 5 out of 6 ciliate species offered as prey. Depending on the experimental conditions and the prey species, predation rates ranged from 0.19 to 10.8 ciliates predator-1 h-1, corresponding to a biomass consumption of 0.001 to 0.33 µg C predator-1 d-1. An overall positive relation between available ciliate biomass and predation rate was found. Comparison of experimental data with field conditions suggests that a considerable part of the ciliate production in fine sandy sediments of the Molenplaat is likely to be consumed by E. longispiculosus, which largely dominates meiofaunal biomass there. Estimated carbon requirements for the predator and production estimates of ciliate and nematode prey at the study site strongly suggest that ciliates are probably a far more important carbon source for E. longispiculosus than nematode prey, at least between late spring and autumn. This implies that carbon transfer from primary producers and bacteria to predatory nematodes may to a large extent be mediated through the microbial food web. In view of the generally high densities and biomasses of ciliates as well as predacious nematodes in fine sandy sediments, similar patterns are to be expected in many other estuarine and marine sediments

Ciliate predation by nematodes in tidal flat sediments

The present study investigates the possibility of a trophic link between ciliates and nematodes in fine sandy sediments of the Molenplaat intertidal flat (Schelde estuary, SW Netherlands). Grazing experiments were conducted under controlled laboratory conditions, with ciliate species isolated from enrichment cultures and nematodes directly collected from the field. Significant reductions in ciliate numbers were found in the presence of the predatory nematode Enoploides longispiculosus, a prominent species (and genus) in fine to medium sandy sediments of the North Sea and adjacent estuaries. No such effects were found when ciliates were inoculated with a mix of mainly deposit-feeding nematodes from the same sampling site. Based on these results, ciliate predation by E. longispiculosus was tested for several benthic ciliate species and abundances, at a range of predator abundances and temperatures, and in the presence of alternative prey (in casu nematodes). E. longispiculosus was capable of significantly reducing densities of 5 out of 6 ciliate species offered as prey. Depending on the experimental conditions and the prey species, predation rates ranged from 0.19 to 10.8 ciliates predator-1 hour-1, corresponding to a biomass consumption of 0.001-0.33 µg C predator-1 day-1. An overall positive relation between available ciliate biomass and predation rate was found. Comparison of experimental data with field conditions suggests that a considerable part of the ciliate production in fine sandy sediments of the Molenplaat is likely to be consumed by E. longispiculosus, which largely dominates meiofaunal biomass there. Estimated carbon requirements for the predator and production estimates of ciliate and nematode prey at the study site, strongly suggest that ciliates are probably a far more important carbon source for E. longispiculosus than nematode prey, at least between late spring and autumn. This implies that carbon transfer from primary producers and bacteria to predatory nematodes may to a large extent be mediated through the microbial food web. In view of the generally high densities/biomasses of ciliates as well as predacious nematodes in fine sandy sediments, similar patterns are to be expected in many other estuarine and marine sediments

Diversity, ecology and the role of protist communities in the Schelde estuary: research by the "Protistology & Aquatic Ecology" group, University Gent (poster)

The section ‘Protistology & Aquatic Ecology’ has been studying the diversity and ecology of planktonic and benthic communities of unicellular eukaryotes (or protists) in the Schelde estuary. The study area involves the entire estuarine gradient, going from the freshwater tidal reaches in the Belgian part of the estuary to the estuary mouth in The Netherlands. Large research efforts were invested in the diversity of protistan communities (diatoms and other micro-algae, heterotrophic flagellates and ciliates) and the biotic and abiotic factors that regulate their structure and composition. In addition, several studies dealt with the role of microbial plankton and benthos in the functioning of estuarine food webs. In these studies, attention was paid to the importance of diversity of microbial communities for fluxes of matter and energy through the estuarine microbial ecosystem. This poster aims at illustrating certain aspects of this research

Le trilemme energétique : une exploration du paysage Belge de l'electricité en l'An 2030

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Ecological implications of life-forms in intertidal benthic diatoms in macrotidal estuaries

Diatom communities inhabiting intertidal estuarine sediments are composed of different life-forms, ranging from adnate epipsammic to free-living epipelic and tychoplanktonic forms. A detailed study of the spatial and temporal distribution patterns of various life-forms in the macro-tidal Westerschelde estuary (South-West Netherlands) revealed that the specific life-form composition of a community has an important influence on its temporal dynamics and might also have major implications for the transfer of diatom-fixed carbon to higher trophic levels. The importance of substrate structure and availability, stochastic (e.g. climate-induced and anthropogenic) hydrodynamic events and the nature and rate of sediment development in regulating the dynamics of these communities are evaluated

Validation of the performance of a GMO multiplex screening assay based on microarray detection

A new screening method for the detection and identification of GMO, based on the use of multiplex PCR followed by microarray, has been developed and is presented. The technology is based on the identification of quite ubiquitous GMO genetic target elements first amplified by PCR, followed by direct hybridisation of the amplicons on a predefined microarray (DualChip® GMO, Eppendorf, Germany). The validation was performed within the framework of a European project (Co-Extra, contract no 007158) and in collaboration with 12 laboratories specialised in GMO detection. The present study reports the strategy and the results of an ISO complying validation of the method carried out through an inter-laboratory study. Sets of blind samples were provided consisting of DNA reference materials covering all the elements detectable by specific probes present on the array. The GMO concentrations varied from 1% down to 0.045%. In addition, a mixture of two GMO events (0.1% RRS diluted in 100% TOPAS19/2) was incorporated in the study to test the robustness of the assay in extreme conditions. Data were processed according to ISO 5725 standard. The method was evaluated with predefined performance criteria with respect to the EC CRL method acceptance criteria. The overall method performance met the acceptance criteria; in particular, the results showed that the method is suitable for the detection of the different target elements at 0.1% concentration of GMO with a 95% accuracy rate. This collaborative trial showed that the method can be considered as fit for the purpose of screening with respect to its intra- and inter-laboratory accuracy. The results demonstrated the validity of combining multiplex PCR with array detection as provided by the DualChip® GMO (Eppendorf, Germany) for the screening of GMO. The results showed that the technology is robust, practical and suitable as a screening too

CO2 intensities and primary energy factors in the future European electricity system

The European Union strives for sharp reductions in both CO2 emissions as well as primary energy use. Electricity consuming technologies are becoming increasingly important in this context, due to the ongoing electrification of transport and heating services. To correctly evaluate these technologies, conversion factors are needed—namely CO2 intensities and primary energy factors (PEFs). However, this evaluation is hindered by the unavailability of a high-quality database of conversion factor values. Ideally, such a database has a broad geographical scope, a high temporal resolution and considers cross-country exchanges of electricity as well as future evolutions in the electricity mix. In this paper, a state-of-the-art unit commitment economic dispatch model of the European electricity system is developed and a flow-tracing technique is innovatively applied to future scenarios (2025–2040)—to generate such a database and make it publicly available. Important dynamics are revealed, including an overall decrease in conversion factor values as well as considerable temporal variability at both the seasonal and hourly level. Furthermore, the importance of taking into account imports and carefully considering the calculation methodology for PEFs are both confirmed. Future estimates of the CO2 emissions and primary energy use associated with individual electrical loads can be meaningfully improved by taking into account these dynamics