MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(AIR-1117-795730) Effects of temperature and oxygen concentration in sediment toxicity testing.

Airas, S¹, Leppanen, M¹, Kukkonen, J¹, ¹ University of Joensuu, Joensuu, Finland

ABSTRACT- Sediment toxicity tests are usually performed in the standardized laboratory conditions to minimize external variation. This system produces useful and comparable results about sediment toxicity for the risk assessment work world wide. Still, site specific evaluation of contaminated sediments creates new challenges because several abiotic factors, like temperature, organic content of sediments and oxygen concentration in water can have a large impact on the actual sediment toxicity at a site. In this study we wanted to focus on the effects of temperature and oxygen concentration in water for the sediment toxicity tests. The tests were performed with two typical test species: an oligochaete Lumbriculus variegatus and a midge Chironomus riparius. Growth, lipid content, feeding rate and reproduction of L. variegatus and growth, survival and emergence of C. riparius were tested in the laboratory in four treatment combinations (I: +20°C 100% O₂ saturation, II: +20°C <40% O₂ saturation, III: +10°C 100% O₂ saturation, IV: +10°C <40% O₂ saturation). Two different sediments were used, LH sediment from a relatively unpolluted lake Hoytiainen and SP sediment from a sawmill pool contaminated with several PAHs, metals and dioxins. Our results indicate that abiotic factors have significant effect on sediment toxicity test results. For example feeding rate and reproduction of L. variegatus were significantly lower in the low temperature treatments (II and IV) than in the treatments I and III. O₂ concentration did not have any observed effect on the endpoints measured with L. variegatus. C. riparius was more sensitive to low O₂ concentration and the growth and survival were significantly affected by the lowered O₂ concentration. We suggest that temperature and other abiotic factors should be taken into account in sediment toxicity testing especially at the sites where the actual conditions largely differ from the laboratory conditions to add environmental realism to sediment assessment work.

Key words: sediment toxicity, lumbriculus, chironomus