At present several dozen standard methods exist for fresh and sea water biotesting using test-organisms of various trophic and systematic levels. In 1994, under the auspices of the International Standards Organization (ISO), a project looked at the international standard of sea water quality. In the project an "algotest" was used, based on growth inhibition of cultures of the sea algae Sceletonema costatum and Phaeodactylum tricornutum (Water quality, 1994), a standard proposed by the Norwegian Institute of Water Research (NIVA, Oslo). Odesa State University and the Odesa branch of the Institute of Biology of the South Seas took part in evaluating the international standard (Water quality, 1994), and in preparing our national standards document "Methods of biotesting sea water and waste water poured into the sea. 211.1.4.047-95" (approved by order N 46 of the Ministry for Environmental Protection, 30 May 1995). These methods permit laboratory based evaluation of the toxicity of sea water of varying salinity and of waste water poured into the sea using cultures of the sea plankton algae Phaeodactylum tricornutum Bohlin and the early nauplial stage of the brine shrimp Artemia salina L. For further development of biotesting methods new species of hydrobionts as test-organisms are necessary. Acquisition and maintenance of pure cultures of these standard test-organisms in the laboratory is of great importance. Because the salinity varies in the waters of the Black and Azov Seas, different culture sets must be used. For this purpose, therefore, the Collection of Cultural Test-organisms was established at the Odesa State University and the Odesa branch of the Institute of Biology of the South Seas. It includes cultures obtained from NIVA and other scientific institutions, and isolated from sea water. Acquisition and maintenance of cultures of test-organisms is an important contribution to biodiversity conservation.