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2N - Field Studies (MOP/125) Incidence of deformed midge (Chironomidae) larvae in contaminated River Kymijoki. Kiiski, Anna1, Hämäläinen, Heikki1, Salo, Simo2, Verta, Matti2, Kukkonen, Jussi 1, 1 University of Joensuu, Joensuu, Finland, Finland2 Finnish Environment Institute, Helsinki, Finland, Finland ABSTRACT- Incidence of mentum deformities in midge (Diptera, Chironomidae: Chironomus spp.) larvae was studied in River Kymijoki, Finland. The sediments of the river are highly contaminated by polychlorinated dioxins, furans and other organic compounds as well as mercury. The main contamination sources were chemical and pulp factories in city of Kuusankoski. The incidence of deformities (DI) was contrasted with a declining contamination trend along the river. Larvae of Chironomus spp. and data on sediment chemistry were collected from 22 sites with depositional soft sediments. Paleolimnological methods were also used to assess the relationship between DI and sediment contamination. One sediment profile sample was taken from a highly contaminated site and another from a less contaminated reference site. Sediment cores were cut into strata of 25 cm, from which subfossil Chironomus spp. head capsules were extracted. Incidence of deformities was estimated for each vertical stratum and contrasted with the respective mercury concentrations. DI abruptly increased up to 54 % right below the factories in Kuusankoski, and decreased along the river with increasing distance. There was a significant association between DI and ITEQ (based on PCDD/F:s concentrations), as well as with DI and mercury. DI also correlated with mercury concentrations in sediment profiles. Deformity incidence in chironomid larvae can be seen at least a potential indicator of nonspecific contamination and a tentative in situ marker of contaminant-induced stress. The use of deformities in bioindication would increase if controlled experiments would reveal contaminants that can induce deformities and those that do not. Key words: Chironomidae, morphological deformities, Chironomus spp., contaminated sediments |
