Bioassay standardization issues in freshwater ecosystem assessment: test cultures and test conditions

The use of bioassays for environment contamination assessment, in particular for aquatic ecosystems, has gained topicality and found extensive applications over the past decades. The methodologies are well established, but the standardization of bioassay conditions needs to be better defined in order to assure applicability as an efficient analytic tool and that results are ecologically relevant. This paper addresses the analysis of the current international situation and the specifics of Russian practice in culturing and use of test organisms for freshwater bioassays. Standardization of bioassays calls for the utilisation of pertinent sources of test cultures and the provision of appropriate cultivation conditions. The paper discusses and reviews recommendations for the selection of test species and their culturing in the context of established ecotoxicological targets and the assessment of sensitivity to various reference toxicants. The significance of the quality of water utilized for test cultures and sample dilution is highlighted. Strict water quality requirements and synthetic media options are analyzed and due consideration is given to temperature and illumination conditions. Toxkit microbiotests are discussed as an alternative to toxicity bioassays alleviating the need for continuous stock test culturing and maintenance