Biomedical subjects

C A Van Gestel

Publications and source records attributed to C A Van Gestel.

11 recordsLinked to original sources

PubMed2001

Polycyclic aromatic hydrocarbon-polluted dredged peat sediments and earthworms: a mutual interference.

In lowland areas of the Netherlands, any peat sediments will gradually become enriched with anthropogenically derived Polycyclic Aromatic Hydrocarbons. Due to Dutch policy standards these (anaerobic) sediments are not allowed to be dredged and placed onto land. Under aerobic conditions, however, biodegradation of PAH is greatly enhanced. This degradation is further stimulated by colonisation of the sediments by earthworms. Laboratory experiments show that although earthworms do not avoid PAH-contaminated sediment, their burrowing-activity is reduced. Furthermore, these sediments have no significant ecotoxicological impacts on earthworms. Experimental introduction of earthworms into PAH-contaminated OECD-soil will result in a decrease in overall PAH content. In field surveys no significant differences in earthworm numbers between locations with fresh and old sediment could be found. It is concluded that dredging of PAH-contaminated sediment poses a very limited environmental threat, and that putting these sediments on land will improve PAH-biodegradation, partly through the colonisation by and activities of earthworms.

Animals↗

PubMed2001

Enchytraeids and microbes in Zn polluted soil: no link between organism-level stress responses and ecosystem functioning.

We studied the presence of zinc tolerance in enchytraeid worm (Cognettia sphagnetorum, Oligochaeta) from a metal-polluted forest soil in The Netherlands. In a dose response experiment, we compared Zn sensitivity, measured as body growth and reproduction, of these enchytraeids with that of animals taken from three unpolluted sites. Because C. sphagnetorum is a keystone species, regulating microbial processes in coniferous forest soil, we performed a microcosm experiment to study the interaction of enchytraeids from several sites with soil microbes. The idea was to study whether there is a link between metal stress response of individuals (tolerance level, life history alteration) and changes observed at higher organization levels of the biological system (trophic interaction and decomposition processes). We did not find evidence for increased metal tolerance of C. sphagnetorum. Worms from the polluted site actually had reduced body growth, indicating negative fitness effects caused by long-lasting metal stress. The density and biomass of the worm population from the polluted site was low in Zn contaminated soil. Presence of enchytraeids enhanced and Zn contamination reduced the activity of microbes in the soil. Enchytraeids from different sites with different life histories and population development, however, had the same effect on microbes. Hence, observed stress responses of individuals and populations could not be linked to density-dependent trophic interactions and ecosystem functioning in the soil-decomposer food chain.

Animals↗

PubMed2001

Toxicokinetics and toxicity of zinc under time-varying exposure in the guppy (Poecilia reticulata).

Levels of toxic substances released into the environment are often highly variable and fluctuate over time. The present study deals with a simple type of time-variable exposure, diluted pulse. We determined toxicokinetic parameters of zinc in guppy fish (Poecilia reticulata) and evaluated the applicability of a toxicokinetics-based survival model developed earlier. In the toxicokinetics experiment, zinc was rapidly taken up and released again; the half-life in fish was only 1.5 d. In the toxicity experiments with diluted-pulse exposure, survival leveled off to a baseline level, which in accordance with the model is explained by the dilution of zinc. The model fitted reasonably well for the lower initial concentrations but tended to overestimate survival rates at the higher concentrations. Toxicokinetic parameters estimated from changes in survival were close to values estimated from measured zinc concentrations in water. Elimination rates during pulse exposure varied from 0.434 to 0.488 d(-1) and corresponded very well to the elimination rate during constant exposure (0.463 d(-1)). Ultimate LC50 values were estimated as 6.40 and 9.10 mg/L. These results suggest that toxicity experiments with a simple, time-varying exposure can be used as an alternative to conventional, constant-exposure experiments. Toxicokinetic parameters and toxicological endpoints can still be estimated in static bioassays with decreasing exposure if the concentration in the medium is measured. At the same time, diluted-pulse experiments may simulate exposure from discharges in the field better than constant-exposure experiments.

Animals↗

PubMed2000

Spatial distribution of trace metals in sediments from urban streams of Semarang, Central Java, Indonesia.

Elevated environmental concentrations of metals are usually associated with the impact of urbanization. The present study is focused on metal contamination in urban sediments. A field survey was carried out to determine the distribution of four metals, i.e., cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn), in the coastal urban area of Semarang, Central Java, Indonesia. Sediment samples were collected from 101 grids of 2x2 km. To map the spatial distribution of these metals, concentrations of each metal were plotted against the corresponding grid coordinate. Cd was below the detection limit (<0.03 microg/g) in all samples, whereas concentrations of Pb, Zn, and Cu fell into a wide range. Frequency distributions of Pb, Zn, and Cu concentrations indicated a similar pattern, in which the major proportion of the sites had a low metal concentration. Some sites, however, had extremely high metal concentrations, Zn up to 1257 microg/g, Pb up to 2666 microg/g, and Cu up to 448 microg/g. The data were used to define background concentrations for sediments in coastal zones of Indonesia ("reference values"). The proposed reference values are 25.6 microg/g, 132.2 microg/g, and 40.7 microg/g, respectively, for Pb, Zn, and Cu. The degree of metal contamination of each individual site was classified according to the calculated value of a combined pollution index, W. Four categories of the degree of metal contamination were proposed, i.e., unpolluted, slightly polluted, polluted, and heavily polluted. Based on this classification, from 101 sites investigated in the greater Semarang area, 51 are unpolluted, 36 slightly polluted, 9 polluted, and 5 heavily polluted.

Cadmium↗

PubMed2000

Associations between trace metals in sediment, water, and guppy, Poecilia reticulata (Peters), from urban streams of Semarang, Indonesia.

The present study aims to answer the question whether the amount of metal in aquatic biota reflects the concentrations in the sediment and water, and whether the physico-chemical properties of the water and sediment have any influence on the suspected relationship. A study was made of 101 small streams in the city of Semarang, Central Java, Indonesia. Data on fish occurrence in 63 streams of the greater Semarang indicated that the guppies did not avoid the highly polluted sites. No significant difference in body weight between sites was found. Significant differences were found in metal body concentrations (Pb and Zn) between fish collected from sites with different degrees of pollution. A significant declining trend of Pb concentrations with increasing organism size was observed, whereas for two other metals, Zn and Cu, the concentrations did not depend on the body weight. Apparently, body concentrations of these two metals are regulated and maintained at a certain concentration. For the relationships between metal concentrations in water, sediment and fish, water and sediment parameters, and fish dry weight, the presence of significant multiple correlations and bivariate correlation (in 17 of 91 pairs of variables) indicated that, in general, abiotic parameters and body size had no influence on the metal flux from sediment to water, and into fish. Results of partial correlation analyses further suggested that metal concentrations in the sediments were the most important factor governing the metal body concentrations of fish. The present study indicates that the guppy Poecilia reticulata from urban streams is a potential bioindicator for urban metal pollution, especially with respect to their (1) spatial distribution over sites of all pollution regimes and (2) variation in metal accumulation levels reflecting the degree of pollution.

Animals↗

PubMed1997

Influence of temperature on the regulation and toxicity of zinc in Folsomia candida (Collembola).

To generate reproducible and reliable results, most protocols for standardized toxicity tests prescribe strict limits for test conditions such as temperature and relative humidity. In the field, however, variability of climate can influence the functioning of organisms and induce changes in sensitivity. To evaluate the influence of temperature on the ecotoxicity of zinc, the springtail Folsomia candida was exposed to zinc-contaminated soil at different temperatures. In one experiment, the toxicity of ZnCl2 was determined at a constant temperature and under alternating temperature conditions. Although control performance of F. candida was influenced by the temperature treatment, effect concentrations for reproduction were not significantly different between treatments. Levels of internal zinc regulation were higher in animals exposed to alternating temperatures. Based on the observed influence of temperature on the accumulation of zinc, a second experiment was performed to determine the sensitivity of F. candida to zinc at four different exposure temperatures. A decrease in temperature led to an increase in sensitivity when sublethal parameters such as growth and reproduction were considered. However, animals were less sensitive at lower temperatures where mortality was concerned. Internal zinc concentrations in the animals increased with decreasing temperatures, and when the effect on reproduction was based on internal zinc levels, differences between temperature treatments were not significant. From the results of this study it is concluded that for F. candida, constant temperature conditions form a good basis for the extrapolation of toxicity levels to fluctuating temperature conditions. Since the average exposure temperature can alter the sensitivity of F. candida for zinc, and changes in sensitivity are parameter dependent, exposure temperature should be chosen carefully.

Animals↗

PubMed1997

Development of zinc bioavailability and toxicity for the springtail Folsomia candida in an experimentally contaminated field plot.

The influence of outdoor exposure conditions and ageing of contamination on the toxicity of zinc was investigated for the springtail Folsomia candida to evaluate the validity of a standardised soil toxicity test. In three successive years, animals were incubated in an experimentally contaminated field plot. During the first months after construction of the test field, total zine concentrations of the soil decreased rapidly due to leaching of excess zinc with rainwater, while increased sorption of the remaining residues resulted in a reduced bioavailability of the metal. Although variation between replicates was substantial, the EC50s for the effect of zinc on reproduction of F. candida determined in the field experiments differed by less than a factor of two from effect concentrations obtained in laboratory tests in which the same soil was used. Expression of the EC50s on the basis of water soluble zinc allowed for a comparison with effect concentrations estimated for other soil types. EC50s were comparable with literature data, which indicates that bioavailability of zinc is the main factor determining toxicity for F. candida. It is concluded that laboratory based toxicity data are suitable to predict effects of zinc for F. candida under outdoor conditions, provided that the bioavailability of zinc is determined accurately using water soluble concentrations.

Journal Article↗

PubMed1995

Sublethal sensitivity index as an ecotoxicity parameter measuring energy allocation under toxicant stress: application to cadmium in soil arthropods.

Toxic substances may affect the life history of a species in a variety of ways. Different species maintain different priorities in coping with the physiological consequences of toxicant-induced stress. This is expressed by changes in energy allocation to different life-history characteristics which may have great consequences for the response at the population level. In this study the terrestrial invertebrates Platynothrus peltifer (Oribatida), Orchesella cincta, Folsomia candida (Collembola), and Porcellio scaber (Isopoda) were chosen to evaluate species-specific sensitivity of life histories. Effects on reproduction and weight increase under exposure to cadmium in the food were analyzed. The answer to the question of which species is the most sensitive depends on the parameter chosen. A comparison of sensitivity on the basis of sublethal effects showed P. peltifer to be the most sensitive species; on the basis of lethal effects however, the species O. cincta was the most sensitive. This discrepancy between effect parameters resulted in differences between the distance of the concentrations at which lethal and sublethal effects occur for different species. The ratio between the lethal effect concentration and the sublethal effect concentration is called the sublethal sensitivity index (SSI) and is proposed as a parameter expressing maintenance of sublethal functions under toxicant stress. The SSI seems to be a valuable parameter for evaluating the likelihood of population-level effects under toxicant stress. To extrapolate effects found in the laboratory to the field situation, more attention should be paid to the relationships between effects on life-history parameters and effects on population growth.

Animals↗

PubMed1994

Patterns of sensitivity to cadmium and pentachlorophenol among nematode species from different taxonomic and ecological groups.

The variation of acute toxicity data among nematode species belonging to different taxonomic and ecological groups was investigated. Twelve different nematode species were extracted from the soil and directly exposed to cadmium and pentachlorophenol. LC50-values were estimated after 24, 48, 72, and 96 h of exposure in aqueous solutions. The species exhibited large differences in sensitivity. LC50-values (72 h) for pentachlorophenol ranged from 0.5 to more than 34.5 mumol/L and for cadmium from 29 to more than 800 mumol/L. These toxicity data could be described by a log-logistic distribution function. LC50-values for cadmium were not correlated with those for pentachlorophenol. Species of the subphylum Secernentia were less sensitive to pentachlorophenol than species of the subphylum Penetrantia, while no differences were observed for cadmium. In addition, no relationship was found between toxicity data and life-history strategies. Slow colonizers (K-strategists, sensu lato) were not more sensitive to cadmium and pentachlorophenol than opportunistic species (r-strategists, sensu lato). Nematodes appeared to be as sensitive to pentachlorophenol as other soil invertebrates. Nematodes were generally tolerant to cadmium.

Animals↗

PubMed1992

Comparison of sublethal and lethal criteria for nine different chemicals in standardized toxicity tests using the earthworm Eisenia andrei.

In this study, the effects of nine different chemicals on the survival, growth, and reproduction of the earthworm species Eisenia andrei were determined using a recently developed method. Earthworms were exposed for 3 weeks to the test chemicals in an artificial soil substrate. Additional data on the acute toxicity of these chemicals were derived from the literature. For some chemicals, cocoon production was the most sensitive parameter (cadmium, chromium, paraquat, fentin, benomyl, phenmedipham), while for others cocoon hatchability was most sensitive (pentachlorophenol, parathion, carbendazim). In the case of parathion, growth of the worms seemed to be even more sensitive than reproduction. As an overall parameter for the effect on earthworm reproduction, the total number of juveniles produced per worm appeared to be a useful parameter. Differences between (acute) LC50 values and the lowest NOEC value for effects on growth and reproduction were different for each chemical. Difference was greatest for cadmium (a factor of greater than 100) and smallest for fentin, benomyl, and pentachlorophenol (a factor of 5-6).

Animals↗

PubMed1992

Validation of earthworm toxicity tests by comparison with field studies: a review of benomyl, carbendazim, carbofuran, and carbaryl.

To investigate whether results of laboratory toxicity tests with earthworms are capable of being used to predict effects in the field, a literature study was carried out. Benomyl, its metabolite carbendazim, carbofuran, and carbaryl were chosen as model substances. From data on the behavior of these pesticides in soil, it can be concluded that shortly after application most of the dosage will be in the top 2.5-cm soil layer. Soil concentrations can be estimated from field dosages used. Estimated field soil concentrations that affected earthworm populations were in agreement with effect levels determined in laboratory studies. In the field, species living in the surface layers (e.g., juveniles of many species) or coming to the soil surface to feed (e.g., Lumbricus terrestris) are most affected, since they experience a high degree of exposure. Evidently, species having long generation times need a relatively long time to recover. Both the distribution of the pesticide and the behavior of earthworms in soil affect earthworm exposure. Insight into these aspects may provide tools to predict both short- and long-term effects of pesticides on earthworm populations in field soils.

Animals↗