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SummaryMotility before and after cryopreservation of Acipenser ruthenus sperm was determined by computer-assisted sperm motion analysis (CASA). In addition, fertility of fresh and frozen/ thawed sperm was tested by in vitro fertilization. Sperm of A. ruthenus was successfully cryopreserved by 1/1 (v/v) dilution with ethylene glycol in final concentrations from 12.5% to 20%.Stepwise cooling using a programmable freezer and fast thawing in a water bath (40°C) for 3 s and 5 s, respectively, resulted in motility rates of 10% to 28% and fry yields of 44% to 94% compared to controls (fresh sperm). With fresh material, different sperm to egg ratios varying from 103 : I to lo6 : I gave similar fertilization rates of more than 90%. Using this cryopreservation method the establishment of sperm banks for endangered sturgeon species and the development of a fertility test for seasonally independent testing seem to be possible. IntroductionExperiments on cryopreservation of the sterlet (Acipenser ruthenus) sperm were carried out in order to examine the possibiliy to (a) establish a sperm bank of the Atlantic sturgeon (A. sturio) and (b) develop a new aquatic bioassay for seasonally independent fertility tests.The Atlantic sturgeon is considered as an extinct species in Germany as well as in many other European countries. Activities

A ring test was carried out within the standardization process of ISO 10872 to evaluate the precision of the toxicity test for the nematode Caenorhabditis elegans. Eight different laboratories tested aqueous solutions of the reference substance benzylcetyldimethylammonium chloride as well as native sediments and soils for toxic effects on the growth and reproduction of C. elegans. Validity criteria were met in all laboratories. Average median- and low-effect concentrations were determined to be 15.1 mg L(-1) (EC50) and 8.7 mg L(-1) (EC10) for growth and 7.5 mg L(-1) (EC50) and 3.8 mg L(-1) (EC10) for reproduction of C. elegans, with ECx values showing a high degree of reproducibility (CV(R) : <21% and <11% for EC10 and EC50, respectively) and repeatability (CV(r) : <20% and <7% for EC10 and EC50, respectively). The toxic effects of the sediments and soils revealed by the different laboratories were well related to each samples' degree of chemical contamination. Moreover, the effects showed an acceptable reproducibility (CV(R) : 5-33% and 0-28% for growth and reproduction, respectively) and repeatability (CV(r) : 3-13% and 0-12% for growth and reproduction, respectively). The present study confirms that the toxicity test with C. elegans according to ISO 10872 is a reliable and precise tool to assess the toxicity of aqueous media, freshwater sediments, and soils.

A whole-sediment toxicity test with Myriophyllum aquaticum has been developed by the German Federal Institute of Hydrology and standardized within the International Organization for Standardization (ISO; ISO 16191). An international ring-test was performed to evaluate the precision of the test method. Four sediments (artificial, natural) were tested. Test duration was 10 d, and test endpoint was inhibition of growth rate (r) based on fresh weight data. Eighteen of 21 laboratories met the validity criterion of r ≥ 0.09 d(-1) in the control. Results from 4 tests that did not conform to test-performance criteria were excluded from statistical evaluation. The inter-laboratory variability of growth rates (20.6%-25.0%) and inhibition (26.6%-39.9%) was comparable with the variability of other standardized bioassays. The mean test-internal variability of the controls was low (7% [control], 9.7% [solvent control]), yielding a high discriminatory power of the given test design (median minimum detectable differences [MDD] 13% to 15%). To ensure these MDDs, an additional validity criterion of CV ≤ 15% of the growth rate in the controls was recommended. As a positive control, 90 mg 3,5-dichlorophenol/kg sediment dry mass was tested. The range of the expected growth inhibition was proposed to be 35 ± 15%. The ring test results demonstrated the reliability of the ISO 16191 toxicity test and its suitability as a tool to assess the toxicity of sediment and dredged material.