Herziening van de indeling in ecologische soortengroepen voor Nederland en Vlaanderen

Herziening van de indeling, zoals die in 1987 werd gepresenteerd (Gorteria, vol. 13, pp. 277-359

How may beach nourishment affect the sandy beach ecosystem? The case of Belgian beaches

Though often regarded as biological deserts, sandy beaches provide a unique habitat for several species. Research was conducted by a consortium of experts with as a first objective to provide an integrated overview of the Belgian beach ecosystem and all its major components. A second objective comprised a review of available literature on the ecological impact of beach nourishment. To meet the first objective, an integrated overview of the Belgian sandy beach ecosystem based on spatial and temporal variation of fauna and flora of 11 sandy beaches is provided. The presented results corroborate the overlooked ecological significance of sandy beaches as a habitat. Besides sedimentology and hydrodynamics, five ecosystem components were taken into account: microphytobenthos, vascular plants, terrestrial arthropods, zoobenthos and avifauna. Nourishment of beaches is a large scale anthropogenic influence on sandy beach ecosystem. Sandy beaches are regarded as systems with a strong resilience towards such impacts. Nevertheless serious (short term) ecological effects can be expected. A review of prior studies indicates that the impact of nourishment is rather case-specific and that it is difficult to draw general conclusions. Short term impact is mostly large due to total mortality of benthic life. It seems very likely that potential recovery from the impact of nourishment will be limited to two essential, species specific pathways: (1) survival by resident organisms and (2) re-colonisation by immigrating individuals, the latter depending on both the dispersal capacities and habitat demands of the organisms. Further research is needed to explore possibilities for reducing detrimental ecological effects. Specific studies are needed towards the survival options, the dispersal capacities and habitat demands of the species present. These should allow for management guidelines to be drawn in terms of preferable nourishment sediment characteristics, timing and practice of the deposition of the sand

Colonisation of Clostridium in the body is restricted to hypoxic and necrotic areas of tumours

The use of gene therapy is one of the most recent molecular strategies for the treatment of cancer. It is essential, however, to have an efficient transfer system by which the desired gene can be delivered to the correct environment. The experiments described in this report investigate apathogenic Clostridium as a possible vector to transfer a specific gene product into the extracellular microenvironment of the tumour which is hypoxic/necrotic in parts, using WAG/Rij rats with transplantable rhabdomyosarcomas as a model. Our data show that Clostridium, after systemic administration of at least 10(7) spores, specifically colonises the hypoxic/necrotic areas of our tumour model, the most efficient species being C. acetobutylicum (NI-4082) and C. oncolyticum. Although spores were also detected in normal tissues for up to 4 weeks, they did not germinate in these tissues. We conclude that it seems likely that these bacteria can be used as a selective transfer system into the extracellular environment of tumours which have hypoxic regions. This strategy would be more tumour-specific than various other strategies that are currently being investigated in anti-cancer gene therapy. (C) 1998 Academic Press.</p