P.J. den Besten

Concepts for the implementation of biomarkers in environmental monitoring

Abstract Biomarkers are promising tools for biomonitoring, both in the marine and freshwater environment. It is however clear that much more information is needed about the exact relation between biomarker responses and the health and fitness of organisms, and even more so between biomarker responses and risks for the ecosystem. In order to address these questions, it is important to realise that the possibilities for the application of a biomarker depend on the concept that is chosen for environmental monitoring. The purpose of monitoring programs varies from simple screening to risk characterisation on the ecosystem level. This paper compares a number of these concepts with respect to how biomarkers can be used and with respect to the specific requirements for further implementation of biomarkers in environmental monitoring.

Sediment quality assessment in the delta of rivers Rhine and Meuse based on field observations, bioassays and food chain implications

The quality of sediment was assessed in 46 sites in the delta of the rivers Rhine and Meuse (The Netherlands) by means of physical-chemical analysis, field observations on the macrobenthic community structure, accumulation studies and bioassays using Chironomus riparius, Daphnia magna and Photobacterium phosphoreum. The results of chemical analyses were classified using national criteria for sediment quality. Results of field studies and bioassays were classified using criteria derived from research in reference areas or based on data from literature. Risk assessment was carried out according to the sediment quality triad and by means of multi criteria analysis (MCA). The Triad approach was used to demonstrate causal relations between effects on the macrozoobenthos community structure, effects demonstrated in bioassays and sediment pollution. This was done by making a comparison of sediment contamination levels with toxicity data from literature for the test organisms of the bioassays. Using the MCA method, for each site a numerical value was derived for total environmental risk in the present situation, based on observed effects. In this way, a relative risk ranking of all sites was realized. The MCA values for the present situation were also compared with MCA scores based on estimated risks after remediation in 1995, in order to set priorities for sites where remediation is expected to cause a significant reduction in environmental risk. In most of the 46 sites studied so far, the macrofauna community was poorly developed, judged by a low number of benthic species, low abundances and a high dominance of species regarded as relatively tolerant to chemical pollution. In bioassays high sediment toxicity was demonstrated for 24 sites. Using the sediment quality triad approach, 25 sites were identified as areas where pollution can be held responsible for the effects observed in the field. From a comparison of contaminant concentrations in different types of food with maximum tolerable risk levels, and the application of a bioaccumulation model it was concluded that the sediment pollution also implies high risks for plant-, benthos- or fish-eating birds (secondary poisoning of top predators). In the Nieuwe Merwede highest MCA risk scores were found for shallow parts where highly polluted sediments are found. It is concluded that the sediment quality triad and the MCA provide additional information which can be used to establish priorities for remedial action. Based on an ecotoxicological evaluation of the improved quality of new sediments that will be deposited after removal of the polluted sediments in the Nieuwe Merwede, it is concluded that in this upstream part of the Rhine delta remedial action will be effective.

DNA strand breaks, cytochrome P-450-dependent monooxygenase system activity and levels of chlorinated biphenyl congeners in the pyloric caeca of the seastar (Asterias rubens) from the North Sea

Seastars (Asterias rubens L.) were collecte d at sampling locations in different areas along transects radiating into the southern North Sea, representing areas impacted by contaminants to different degrees. Strand breakage in DNA isolated from tissue of the pyloric caeca was measured by the alkaline unwinding assay, modified to allow for the isolation of highly intact DNA. The interpretation of the results is based on the incidence of DNA strand breaks (expressed as the double:total DNA ratio or F value, indicating the degree of double-strandedness). The cytochrome P-450 concentration and the benzo [a] pyrene (BaP) hydroxylase activity were measured in microsomal fractions of the pyloric caeca. The chlorinated biphenyl (CB) congeners in tissue samples from the digestive gland were determined by temperature-programmed gas-chromatography, with a CPSil8 capillary column as the stationary phase, hydrogen as the carrier gas and 63Ni-electron capture detection. Areas where seastars showed different DNA integrity could be described. The highest integrity (0.75 < F < 0.85) was found in the off-shore reference sites of the Dogger Bank and Southern Bight. The mean F value in seastars from most sampling locations varied between 55 and 75%. The lowest DNA integrity (0.35 < F < 0.55) was found in specimens obtained from sampling locations near the river Rhine delta, along the Dutch coast and at two expected uncontaminated offshore areas. The BaP hydroxylase activity was relatively high near the mouth of the rivers Rhine and Scheldt, but also at a supposedly clean site near Dogger Bank. The concentration of CB congeners in the pyloric caeca of seastars decreased along transects radiating into the southern North Sea from the coastal areas of the Netherlands; the highest concentrations were in the nearby coastal areas and the lowest were in the open sea sampling locations. The data indicate that there might be a relationship between pollution from the Rivers Rhine, Meuse and Scheldt and the incidence of DNA strand breaks and/or BaP hydroxylase activity

In situ Bioassays with Chironomus riparius : Laboratory-Field Comparisons of Sediment Toxicity and Effects During Wintering

A field bioassay was developed to study the in situ effects of sediment contamination on Chironomus riparius larvae. The survival, development rate and increase in Chironomus larvae biomass was compared between laboratory bioassays with the field cages. The incidence of mentum deformities was compared not only between laboratory and field bioassays but also with observations on field populations of Chironomus larvae. Survival in the field bioassays was slightly higher than the laboratory, except at locations with known contamination of the surface water. The influence of surface water quality in field bioassays was demonstrated in translocation experiments, in which clean sediment was placed in a polluted site, and vice versa. In a field bioassay carried out in the autumn, an inverse relationship between the rate of development and the initial larval density in the field cages was apparent. In addition, in the field bioassays with C. riparius considerable seasonal variation in the survival and incidence of mentum deformities was found. Field bioassays performed during the winter season indicate that low temperatures can interact with or add to the effects of sediment contamination on chironomid populations.

Relation between responses in the neutral red retention test and the comet assay and life history parameters of Daphnia magna

Responses of the neutral red retention (NRR) assay as test for lysosomal stability and the comet assay as test for DNA integrity were measured in the water flea, Daphnia magna, and compared with mortality and effects on population growth rate during short- or long-term exposure to seven different toxicants. The NRR test and the comet assay were performed with fresh preparations of pieces of tissue from the digestive tract or with cell preparations from whole daphnias. Five toxicants caused responses of the NRR test or the comet assay after short-term exposure at concentrations below the acute toxicity level. Preliminary results of long-term exposure experiments suggest that these biomarker responses can be related to chronic effects on survival and/or reproduction of D. magna. This type of research should provide the basis for future use of the NRR test and the comet assay as early warning biomarkers for effects of toxicants on Daphnia populations.

Use of Sediment Quality Guidelines in Ecological Risk Assessment of Dredged Materials: Preliminary Reflections

Ecological risk assessment appears as an useful approach for dredged materials. It is often proposed in the form of a tiered approach, the first tier relying upon a chemical characterisation of sediments, and a simplified risk assessment based on sediment quality guidelines. A recently proposed tiered framework, relying upon published sediment quality guidelines and a mean quotient approach at the first tier, is tested against two databases: one including bioassays results and chemicals concentrations of contaminated and non-contaminated sediments; and the second chemical concentrations in sediments from two French regions. The selected sediment quality guidelines seem reliable, as the incidence of type I and type II errors remain in accordance with their definitions. However, the relevance of this statement is somewhat limited by the size of the database used. Moreover, geochemistry may play a confusing role for some metals like Ni and Cr. The cut-off values initially proposed for the first tier appear questionable: the lower boundary allows discarding of a low proportion of sediment samples in the chemicals only database, and toxicity may be observed below this value. Conversely, the upper boundary value may be considered as too low, as a significant proportion of non-toxic samples may be observed above this value, and as a large number of sites in the chemicals only database would enter higher tiers of the framework. Further tests and development are needed with an extended database.

Statistical analysis of sediment toxicity by additive monotone regression splines

Modeling nonlinearity and thresholds in dose-effect relations is a major challenge, particularly in noisy data sets. Here we show the utility of nonlinear regression with additive monotone regression splines. These splines lead almost automatically to the estimation of thresholds. We applied this novel method to explore the relation between the toxicity of aquatic sediments, as observed in bioassays with Daphnia magna, Chironomus riparius and Vibrio fischeri, and the degree of contamination of the sediments. Despite the low signal-to-noise ratio in the data, some interesting thresholds and (non)linear effects were found. The method has added value compared to the linear multivariate methods applied earlier to these data. Percentages of explained variance remained low, but could be doubled by diminishing the effect of local variability.

Environmental risk assessment on aquatic-terrestrial gradients in a freshwater tidal area

Environmental risk assessments are generally performed for either terrestrial or aquatic systems, while these systems sometimes exist in close proximity. The objective of this study is to compare environmental risks along gradients from aquatic to terrestrial conditions. The assessment involved chemical analysis (including bioavailable fractions), as well as bioassays and bioaccumulation experiments using aquatic and terrestrial organisms. The results demonstrate that sediments and soils from neighbouring aquatic and terrestrial systems may render different assessments in terms of environmental risks. Metal availability for oligochaetes appeared to be limited in the aquatic environment as compared to the terrestrial environment, while the reverse was observed for organic contaminants. This paper aims to illustrate the use of various assessment techniques within a framework to compare ecological risks in aquatic and terrestrial environments. The obtained results are useful when considering (a prioritisation of) remedial actions.

Preface: Barometers of Aquatic Ecosystem Health and Integrity

This special issue is an outcome of the 6th International Conference on Aquatic Ecosystem Health and Management held in Amsterdam (4–7 November, 2001). The conference was organized by the Aquatic Ecosystem Health and Management Society (AEHMS) and the National Institute for Inland Water Management and Waste Water Treatment (RIZA). The overall purpose of the Conference and special issue is to generate improved understanding of the status and health of aquatic ecosystems and their capacity to support human activities dependent on resources and functions derived from these systems. The theme reflects awareness of ecosystem health in scientific and management circles, the increased development of ecotechnologies (tools and techniques in ecology), and the challenging complexity of integrating such issues as ecosystem integrity, biodiversity, and sustainable development. The focus of the special issue is on ecotechnology (conceptual and applied aspects) and integration in aquatic systems. In addition to this special issue a peer reviewed book was launched based on invited contributions entitled Biological testing in marine and freshwaters: Trends, Relevance, and Linkages to Ecosystem Health (Eds: P. den Besten and M. Munawar). The book is under preparation and expected to be published under the Ecovision World Monograph Series, sponsored by the AEHMS. A number of insights have been gained from the Conference and the compendium of ten papers included in this special issue presents excellent coverage of various regions of the world such as Australia, Middle East, UK, Switzerland, Germany, and USA. Many of the topics covered are actually problems or questions, often not fully expounded, rather than solutions. Given that the statement of the overall problem/objectives is a key component of aquatic governance this issue can be considered useful and significant. We sincerely thank the Dutch National Institute for Inland Water Management and Waste Water Treatment (RIZA) for financial support and hosting the conference. We also thank other sponsors: Dutch National Institute for Coastal and Marine Management (RIKZ), AquaSense Consultants (Netherlands) and the Society for Toxicology (NVT), section Environmental Toxicology (Netherlands) for sponsorship. We are grateful to Cees van de Guchte and Anton. Gerritsen, for their support and assistance. The assistance of I. F. Munawar, D.F. Malley, K. Bonnell, N.F. Munawar, and H. Hamdani on behalf of AEHMS is greatly appreciated. Thanks are also due to H. Pruys and A. Brackel of CAOS (Amsterdam) for managing the conference secretariat and making local arrangements.