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2K - Sediment Assays (TUP/147) Improved Method for Testing Effects on the Sediment Dwelling Freshwater Blackworm ( Lumbriculus variegatus, Müller). Hargreaves, Thomas1, Kelly, Craig1, Carson, Damien1, 1 Inveresk Research, Tranent, East Lothian, Scotland ABSTRACT- The freshwater Blackworm (Lumbriculus variegatus, Müller, (Lumbriculida: Lumbriculidae)) is a ubiquitous species of freshwater sediments. It has been proposed as an ecologically relevant model for determining effects of chemicals with a propensity to partition to sediment. It is also considered as an appropriate model for conducting bioaccumulation studies with sediment, because of its behaviour, size and because it usually exhibits architomy as a means of asexual reproduction. The UK Environment Agency expressed concerns that the method of daily supply of clean feed allowed a period of depuration during the exposure period. This was regarded as a flaw in the method, as continuous exposure was not assured and it moderated exposure conditions. Food provided once a day from the surface water was also thought likely to alter the worm's feeding strategy and could encourage the organisms to leave the sediment, reducing exposure. This study investigated a method whereby appropriate feed was added to the artificial sediment prior to the start of the test. No further feeding occurred for the 28-day duration of the study. By careful contol of dissolved oxygen levels, worm numbers increased by a factor of three in this time, indicating worm survival and growth was acceptable. The worm biomass was also within an expected range for the species. It is proposed that this method of feeding promotes more natural behaviour in the test organism and more accurately reflects the expected exposure risk for the test organism from sediments. It also gives continuous controlled exposure and is more suited for use in bioconcentration studies. Key words: sediment toxicity, Lumbriculus variegatus, feeding, survival |
