Evaluation of the toxicity of river and creek sediments in Hungary with two different methods

The aim of this study is to compare the responses of two different ecotoxicological methods for the determination of the toxic hazard of river or creek sediments in Hungary. Since water quality is intrinsically linked to sediment quality, the ecotoxicological control of sediments is also very important in the water quality policy. The 2000/60 EC Water Framework Directive aims at achieving a good qualitative and quantitative status of all water bodies by 2015. Fifteen sediments and four sludges were collected at different sites in Hungary, which are contaminated by industrial sewage. The first assay is the acute toxicity test with the crustacean Daphnia magna Straus (OECD 202) using larvae less than 1 day old, and an exposure time of 2 days. The second assay is the Ostracodtoxkit F with freshly hatched larvae of the crustacean Heterocypris incongruens and an exposure time of 6 days. The Ostracodtoxkit F test is a "direct sediment contact" bioassay, in which the test organisms are in continuous contact with the sediments. The Daphnia tests were applied on water extracts of the sediment without any contact of the test organisms with the contaminated sediment. The same 1:4 water/sediment ratio has been applied to both tests. The results showed higher toxic effects of the sediments to H. incongruens than to D. magna confirming the need to complement "water only" tests with "solid phase" assays for a meaningful evaluation of the toxic hazard of aquatic environments. The sensitivity of H. incongruens is similar to that of the other test species which are currently used for solid-phase assays. The growth inhibition of H. incongruens is a very sensitive endpoint for sediment toxicity testing. The sediment toxicity tested by ostracods showed strong correlation with concentration of total chromium, lead, and cadmium together.