G. van Geest | Radboud University Nijmegen (original) (raw)

Papers by G. van Geest

River Systems, 2006

Recovery of the fish community of the river Rhine focussed mainly on the return of migratory spec... more Recovery of the fish community of the river Rhine focussed mainly on the return of migratory species, in particular the Atlantic Salmon, Salmo salar, and to a lesser extent on rheophilic fish species. Several limnophilic species that characterize remote parts of the floodplains are, however, also endangered. The status of the fish communities in the floodplains is little known and has been neglected so far. To fill this gap, the present study investigated fish communities in floodplain lakes along the lower River Rhine. To assess how these lakes contribute to fish species richness in the river-floodplain system, the community structure is compared to that in the main channel and to connected backwaters, e.g. side channels, which had been investigated more intensively in recent years. Floodplain lakes with abundant vegetation may have low fish species richness, but they are the only sites with suitable habitats for the reproduction of limnophilic species such as tench Tinca tinca, rudd Scardinius erythrophthalmus and crucian carp Carassius carassius. Limnophilic species in most of these lakes are, however, outnumbered by eurytopic species such as bream Abramis brama, which indicates that the original lateral gradient is truncated with an almost complete loss of`black fish' habitats in the present active floodplains along the lower Rhine. Floodplain lakes with abundant vegetation should be carefully preserved because they represent original aquatic components that have declined markedly, and they need decades to develop. Preservation of these lakes would enhance the conservation of characteristic limnophilic species. Retention areas outside the present active floodplain ± retained as a component of flood risk management ± may provide the opportunity to rehabilitate or

Hydrobiologia, 2003

... COVALIOV Silviu (1) ; VAN GEEST Gerben (2) ; HANGANU Jenica (1) ; HULEA Orieta (1) ; TÖRÖK Li... more ... COVALIOV Silviu (1) ; VAN GEEST Gerben (2) ; HANGANU Jenica (1) ; HULEA Orieta (1) ; TÖRÖK Liliana (1) ; COOPS Hugo (3) ; ... Delta National Institute, 165 Babadag Str., 8800 Tulcea, (2) Wageningen University, PO Box 8080, 6700 DD Wageningen, PAYS-BAS (3) RIZA, PO ...

Ecological Indicators, 2014

Two questions are central to the work in this thesis: 1. What are the factors determining macroph... more Two questions are central to the work in this thesis: 1. What are the factors determining macrophyte composition in floodplain lakes along the Lower Rhine? 2. What advice can be given for design of future water bodies?

Linking wetland restoration to WFD objectives ..

Met de komst van de KRW (EP 2000) en stroomgebiedbeheersplannen met bijbehorende maatregelpakkett... more Met de komst van de KRW (EP 2000) en stroomgebiedbeheersplannen met bijbehorende maatregelpakketten is er veel aandacht voor de wijze waarop maatregelen uitgevoerd kunnen worden. Vragen die hierbij centraal staan zijn: welke inrichting levert het hoogste ecologische rendement en hoe kunnen beheer en onderhoud tot een minimum beperkt worden? In opdracht van Rijkswaterstaat voert Deltares daarom studies uit die gericht zijn op de ontwikkeling en montage van kennis over de ecologische effectiviteit van maatregelen in Rijkswateren, in samenhang met hydromorfologische stuurvariabelen. De hier besproken studie wordt in 3 delen opgesplitst: - een oevertypologie aan de hand van bestaande natuurvriendelijke oeverconstructies; - een literatuuronderzoek naar de huidige kennis met betrekking tot (ecologisch effectieve) inrichting van natuurvriendelijke oevers; - een literatuuronderzoek naar de huidige kennis met betrekking tot beheer en onderhoud.

Halverwege vorige eeuw waren de strangen van de Rijn, maar ook de hoofdstroom, rijk begroeid met ... more Halverwege vorige eeuw waren de strangen van de Rijn, maar ook de hoofdstroom, rijk begroeid met waterplanten. Tegenwoordig zijn waterplanten echter beperkt tot de stroomafwaartse delen van de hoofdstroom, en ze komen langs andere trajecten vrijwel niet meer voor. Ook in herstelprojecten die de afgelopen decennia langs de Rijn zijn uitgevoerd, komen in deze wateren nauwelijks waterplanten tot ontwikkeling. In dit artikel analyseren we de rol van het rivierpeil voor waterplanten en we geven aanbevelingen voor ecologisch herstel van riviergebonden waterplantenvegetaties

A literature review of freshwater model ecosystem studies with herbicides was performed to assess... more A literature review of freshwater model ecosystem studies with herbicides was performed to assess the NOEC[sub]ecosystem for individual compounds, to compare these threshold levels with water quality standards, and to evaluate the ecological consequences of exceeding these standards. Studies were judged appropriate for this purpose if the test systems simulated a realistic freshwater community, if the experimental design was generally sound (ANOVA or regression design, exposure concentrations described), and if published not earlier than 1980. Almost half of the collected papers did not meet these selection criteria. Effects were classified according to their magnitude and duration. The most sensitive endpoints for photosynthesis inhibitors, the most widely studied group of herbicides, were responses related to community metabolism and the structure of phytoplankton, periphyton and macrophytes. These endpoints showed a clear dose-response relationship. The criteria as set by the Uni...

Archiv für Hydrobiologie. Supplementband. …, 2005

Water bodies in large-river floodplains are typically dominated by aquatic vegetation. The propor... more Water bodies in large-river floodplains are typically dominated by aquatic vegetation. The proportion of macrophyte-dominated lakes varies between years, depending on annually different water-level fluctuations within the lakes. We reanalysed aquatic-vegetation inventories made over five decades in floodplain lakes along the Lower Rhine, and related them to summer inundation and drawdown events. We observed a lower probability of submerged macrophyte dominance (lake cover > 20 %) after inundation in summer, with contrasting responses for different species. Lake-bottom exposure during prolonged low water stages had an opposite effect, resulting in an increased probability of dominance by submerged vegetation and a decrease of nymphaeid vegetation. Our results indicate that under the current, hydromorphologically modified, conditions a small proportion of water bodies in the floodplains has abundant aquatic vegetation, unless new sites are repeatedly created which provide opportunities for colonization. The results are important for management as they help in defining the ecological status of floodplain lakes.

River Research and Applications

The Volga is the longest river in Europe and 16th longest in the world. The riverine landscape of... more The Volga is the longest river in Europe and 16th longest in the world. The riverine landscape of the Volga is of exceptional scientific and economic importance to Russia; the basin contains approximately 40% of the Russian population and relates to 45% of the country's industrial and agricultural produce. The Volga River drains an area of 1.4 million km2, covering various biomes from taiga to semidesert. Anthropogenic impacts in the 20th century include pollution as well as hydropower production and navigation purposes, incurring a cost for its historically important migratory fish (e.g., sturgeons) and related fisheries. River basin management in Russia, since 2006, is based on the water code that determines federal competencies in water management. Extensive water quality monitoring programmes provide feedback to regional managers. Monitoring of biological parameters is spatially limited and should be extended in order to provide sufficient data for informed management. Some initiatives have been implemented in recent decades in order to restore the ecological health of the river and manage fisheries resources (e.g., restocking programmes and the definition of total allowable catches). As recreational fishing is popular but presently unregulated in Russia, we suggest additional monitoring. Finally, the headwaters and lower river floodplain of the Volga have remained as free‐flowing and relatively undisturbed systems. Because reference conditions with low levels of anthropogenic disturbance cannot be found in Central European lowland rivers, both the headwaters and lower Volga floodplains below Volgograd are of great importance on European level.