W4 PM Sediment Quality Assessment
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in Ballroom 4

(KII-1117-794618) Assessing biological risk of sediment contamination by use of midge (Chironomidae) larval deformities.

Kiiski, A.¹, Hämäläinen , H.², Salo, S.³, Verta, M.³, Kukkonen, J.¹, ¹ Univeristy of Joensuu, Finland² University of Jyväskylä, Finland³ Finnish Environmental Institute, Finland

ABSTRACT- Morphological deformities in midge (Chironomidae, Chironomus spp.) larvar have been frequently observed in sediments contaminated by different xenobiotics. Deformity formation is considered to be a sublethal, teratogenic response to contamination. In the laboratory, deformities have been induced with some toxicants and a few dose-response relationships have been documented. However, the results are largely inconsistent and a more detailed description and quantification of the deformity-contamination relationship is still needed. It is equally important to investigate if deformities in individuals are indicative of ecologically significant responses at higher levels of biological organization. Depositional soft sediments along river Kymijoki (Finland) are highly contaminated e.g. by dioxins/furans and mercury due to effluents from a former chemical factory and a paper mill. Benthic invertebrate samples for assemblage structure analysis, midge larvae for deformity analysis and sediment samples for physical and chemical characterization were taken from 22 sites varying in contamination level. In addition, three long sediment cores were analyzed for deformities in midge subfossil head capsules and sediment mercury concentration. Significant relationships between deformities and sediment contamination were observed both spatially and temporally. Ordination analysis showed that invertebrate assemblages in the most contaminated sites differed from those in other sites. However, adverse effects on communities (species loss, decrease in abundance or taxa richness) could not be detected. Furthermore, in contrast to what expected, invertebrate abundance and richness were positively associated with deformity incidence. Sediment organic enrichment, which was correlated with contamination, seems to strongly affect the assemblage structure and could mask the effects of contaminants. The results suggest that incidence of deformities in chironomid larvae can be used as an indicator of sediment contamination. However, more information is needed to confirm if the incidence of deformities reflects ecologically significant effects in river ecosystem.

Key words: morphological deformities, Chironomidae, benthic invertebrates