Papers by Rick Wortelboer
Aquatic Ecology, 1995
Laboratory incubation experiments were used to study the effect of reduced concentrations of orga... more Laboratory incubation experiments were used to study the effect of reduced concentrations of organic micropollutants in water from the rivers Rhine and Meuse on the specific growth rate of the river phytoplankton community. Before incubation, part of the water sampled was treated with XAD-4 and XAD-8 resins to absorb dissolved organic compounds. Four dilutions were made by mixing untreated water with XAD-treated water in the ratios 100:0 (control), 70:30, 40:60 and 0:100. The phytoplankton specific growth rate increased significantly with the increased fraction treated with XAD in all but one incubation experiment. In these experiments, the specific growth rate was on average 9% higher in the fraction in which 100% was treated with XAD than in the controls. In the Rhine and Meuse river water, phytoplankton growth seemed to be inhibited by organic compounds. This inhibition was ascribed to the presence of dissolved organic micropollutants. Removing organic micropollutants using XAD resins to study the toxic effects of these compounds on field phytoplankton communities can be concluded to be a promising tool for risk assessment of micropollutants but needs to be supported by additional methodological research.
Het klimaat verandert in Nederland: de gemiddelde temperatuur is over de afgelopen eeuw gestegen,... more Het klimaat verandert in Nederland: de gemiddelde temperatuur is over de afgelopen eeuw gestegen, de hoeveelheid en de intensiteit van de neerslag zijn toegenomen en zeer warme dagen komen vaker voor. • Verschillende effecten van klimaatverandering zijn in Nederland al waarneembaar. Sommige effecten zijn positief, zoals een toename van de landbouwproductie en van het aantal gunstige recreatiedagen. Andere zijn negatief, zoals een toename van wateroverlast en een afname van de kwaliteit van het oppervlaktewater (watertemperatuur, algengroei) en van biodiversiteit. Een versnelde zeespiegelstijging en een toename van de piekafvoeren van de rivieren als gevolg van klimaatverandering zijn in Nederland vooralsnog niet waargenomen. • Klimaatverandering en de effecten daarvan zullen naar verwachting de komende eeuwen doorzetten. Negatieve effecten van klimaatverandering hangen vooral samen met veranderingen in het optreden van extreme weerssituaties (droogte, noodweer, hittegolven en dergel...
In 2003-2012, the Dutch Swift Society (GBN) installed cameras at nests of Common Swifts, with the... more In 2003-2012, the Dutch Swift Society (GBN) installed cameras at nests of Common Swifts, with the aim of learning more about the swifts’ breeding biology without disturbing their nests. In total 376 clutches were monitored, distributed over 43 villages and cities in the Netherlands. In the later years of the study more than 80 cameras were operational.
Arrival dates of first parents were relatively constant, varying between 17 and 30 April. In some years (e.g.
2010) egg laying was postponed because of the cold weather. The shortest observed incubation period lasted 17
days; the average length was 21 days. The nestling period lasted on average 42 days, with no differences
between successive young, but with considerable variation. The times of first flight of the young Swifts showed a daily pattern with a preference for fledging in the dusk.
The average numbers per clutch of eggs, nestlings and fledged young were 2.46, 1.99 and 1.79, respectively. These numbers were higher in clutches started early in the breeding season. On average, 80% of clutches
successfully raised young until fledging. Replacement clutches increased this proportion to 90%. Breeding success in natural nest sites was on average 15% lower than that in artificial sites (nest boxes and special roof tiles with an entrance for Swifts).
Average breeding success over all clutches showed no relation to mean temperature, hours of sunshine and
duration of precipitation when using yearly mean values. However, when using data of individual clutches and local weather during the exact nesting periods, multiple linear regression showed significant effects of weather conditions on number of young fledged, egg survival, nestling survival and proportion of successful clutches.
Temperature was the dominant factor showing suboptimal responses at both low and high temperatures, especially in natural nest sites. This might indicate unfavourable conditions for the young in nests in natural nest sites in warm summers.
Effecten van ingrepen in het waterbeheer op aquatische levensgemeenschappen. Soortbenadering, fas... more Effecten van ingrepen in het waterbeheer op aquatische levensgemeenschappen. Soortbenadering, fase 1: ontwikkeling van het prototype. A.M. Durand (W+B) E.T.H.M. Peeters (LUW) F.G. Wortelboer (RIVM) P M "an den ~o o m a n d r s M P Grlmm
Om de effecten van zandhonger tegen te gaan zijn op veel plaatsen stenen dammetjes aangelegd.
Hydrobiologia, 1990
External phosphorus loads to three shallow lakes in the Netherlands were reduced by eliminating w... more External phosphorus loads to three shallow lakes in the Netherlands were reduced by eliminating waste-water discharge and by dephosphorization of the supply water, with which water level is controlled. Concentrations of total-phosphorus and chlorophyll a were significantly reduced during 1980–1986 in L. Breukeleveen, but not in L. Vuntus and L. Loosdrecht. In 1983–1986 the phosphorus flow through several trophic levels
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Papers by Rick Wortelboer
Arrival dates of first parents were relatively constant, varying between 17 and 30 April. In some years (e.g.
2010) egg laying was postponed because of the cold weather. The shortest observed incubation period lasted 17
days; the average length was 21 days. The nestling period lasted on average 42 days, with no differences
between successive young, but with considerable variation. The times of first flight of the young Swifts showed a daily pattern with a preference for fledging in the dusk.
The average numbers per clutch of eggs, nestlings and fledged young were 2.46, 1.99 and 1.79, respectively. These numbers were higher in clutches started early in the breeding season. On average, 80% of clutches
successfully raised young until fledging. Replacement clutches increased this proportion to 90%. Breeding success in natural nest sites was on average 15% lower than that in artificial sites (nest boxes and special roof tiles with an entrance for Swifts).
Average breeding success over all clutches showed no relation to mean temperature, hours of sunshine and
duration of precipitation when using yearly mean values. However, when using data of individual clutches and local weather during the exact nesting periods, multiple linear regression showed significant effects of weather conditions on number of young fledged, egg survival, nestling survival and proportion of successful clutches.
Temperature was the dominant factor showing suboptimal responses at both low and high temperatures, especially in natural nest sites. This might indicate unfavourable conditions for the young in nests in natural nest sites in warm summers.
Arrival dates of first parents were relatively constant, varying between 17 and 30 April. In some years (e.g.
2010) egg laying was postponed because of the cold weather. The shortest observed incubation period lasted 17
days; the average length was 21 days. The nestling period lasted on average 42 days, with no differences
between successive young, but with considerable variation. The times of first flight of the young Swifts showed a daily pattern with a preference for fledging in the dusk.
The average numbers per clutch of eggs, nestlings and fledged young were 2.46, 1.99 and 1.79, respectively. These numbers were higher in clutches started early in the breeding season. On average, 80% of clutches
successfully raised young until fledging. Replacement clutches increased this proportion to 90%. Breeding success in natural nest sites was on average 15% lower than that in artificial sites (nest boxes and special roof tiles with an entrance for Swifts).
Average breeding success over all clutches showed no relation to mean temperature, hours of sunshine and
duration of precipitation when using yearly mean values. However, when using data of individual clutches and local weather during the exact nesting periods, multiple linear regression showed significant effects of weather conditions on number of young fledged, egg survival, nestling survival and proportion of successful clutches.
Temperature was the dominant factor showing suboptimal responses at both low and high temperatures, especially in natural nest sites. This might indicate unfavourable conditions for the young in nests in natural nest sites in warm summers.