New ecotoxicological techniques

Contamination of marine and freshwater sediments is a major problem with large costs being involved. To address this problem, there is an increasing need for biological assessment methods to complement the original chemical-based risk assessment. Therefore, the department aims to utilize the ecotoxicological insight in the benthic system to develop new biological test instruments to determine ecologically relevant effects of polluted sediments and water systems. To implement new techniques in research and regulation, the development and design of new techniques is realized in close cooperation with other research institutes and policy makers, local water administrations, consultancy agencies and contract laboratories.

Example 1: a new fluorescence based toxicity test using Lemna minor

The desire to enable faster determination of the potential impact of contaminants on higher freshwater plants initiated the development of a new automated toxicity test using in vivo chlorophyll fluorescence parameters, measured with the rapid, sensitive and cost-effective pulse-amplitude-modulated (PAM) fluorescence technique, as toxicity endpoints and the free-floating macrophyte Lemna minor as test organism. This test has a capacity to assess single contaminant induced negative effects in aquatic plants after only 24 hours of exposure, which is considerably faster than the duration of the widely used standardized duckweed growth inhibition test. The fast and automated procedures of the fluorescence based Lemna minor toxicity test makes it simple to use and therefore a promising tool for improvement of future risk assessment or screening of large numbers of water samples.

Example 2: A new algal toxicity test

Using the same pulse-amplitude-modulated (PAM) fluorescence technique as in the new Lemna minor test (see example 1 above), a toxicity test using green algae was also developed. Using the actual photochemical yield as endpoint, the algae respond very quick to adverse effects of contaminant: within 4 hours of exposure these effects can be quantified. Combined with the automated procedures, this makes this test very useful to screen large number of water samples, either collected in the field or prepared in the laboratory to test ranges of toxicant concentrations.

Example 3: A new sediment toxicity test with a sediment dwelling cladoceran

A whole sediment toxicity test using a benthic cladoceran Chydorus sphaericus was developed, as an alternative for the use of pelagic daphnids. A C. sphaericus laboratory culture was started and its performance under control conditions was optimized. The test was validated by determining dose-response relationships for aqueous cadmium and copper, showing a sensitivity of C. sphaericus similar to that of daphnids. A validation was performed with a series of contaminated sediments from polluted locations and a significant negative correlation between survival and toxicant concentrations was observed. This newly developed test using the benthic cladoceran C. sphaericus is suitable for routine laboratory sediment toxicity testing.

Dekker, T., G.D. Greve, T.L. ter Laak, M.E.Y. Boivin, B. Veuger, G. Gortzak, S. Dumfries, S.M.G. Lücker, M.H.S. Kraak, W. admiraal and H.G. van der Geest, 2006. Development and application of a sediment toxicity test using the benthic cladoceran Chydorus sphaericus. Environ. Pollut. 140: 231-238.

Example 4: A new toxicity test with the riverine mayfly Ephoron virgo

The diversity of aquatic insects in large European rivers has been strongly reduced during the past century. Therefore, aquatic insects can play a key role in indicating ecological recovery of large rivers. However, there is a lack of ecological and ecotoxicological knowledge of riverine insect species. To provide this basic knowledge, development of ecotoxicity tests with riverine insect species is necessary and therefore cultures or storage of field collected eggs of these species in the laboratory are needed. Therefore, a method for collecting and storing eggs of the riverine mayfly Ephoron virgo and a reliable ecotoxicity test using newly hatched larvae were developed. This test can be used for determining dose-response relationships for toxicants as well as for testing water and sediment samples.

Insects in polluted rivers: an experimental analysis. 
PhD thesis Harm van der Geest, February 22, 2001. ISBN 90-901447-14 pp 152.