(water, mud, vegetation thickets, etc.), and degree of sensitivity to 

 toxicants. The latter is specific for each species and varies within a 

 very great range: from nannograms to milligrams and grams per litre 

 (Alekseev, 1970). Investigations of both Soviet (Alekseev and Antipin, 

 1976; Filimonova, 1974; Anon., 1975) and the filter feeders (especially 

 the cladocerans) are the most sensitive test organisms, and hence, the 

 most widely used. Different species of Cladocera, however, have their 

 own specific sensitivity, and between the laboratory test cultures (pure 

 lines) and natural populations there are also substantially great dif- 

 ferences in resistence to toxicants. 



In the world literature there are a number of biological tests sug- 

 gested. These have been described in appropriate reviews (Katz, 1971; 

 Stanislawska, 1969). Many of these tests have not received international 

 recognition, and are being used primarily within national laboratories, or 

 have been encorporated within the limits of regional agreements (Anon., 

 1966). 



The present communication deals mainly with the authors' efforts, 

 representing a contribution of one laboratory to the given problem. Since 

 algae are used only rarely for toxicological testing, the topic will be 

 discussed in some detail. 



Test cultures of algae are grown either as pure cultures, or as 

 samples from natural waters at the time of mass development of some 

 species (e.g., St&pkanocLLi>cuA kantzckti in spring, or hlLciocyAtiA tx<inj±- 

 gZno6a in summer). There may be essential differences between the re- 

 sults obtained on these species, since laboratory cultures are more deli- 

 cate, and have been developed under artificial conditions, frequently on 

 complex media. However, the benefits of uniform results and synchrony 

 cannot be overlooked. 



The simpliest test is the one involving the death of the unicellular 

 algae in the presence of toxicants. A quantitative ratio of living to 

 dead cells in the test culture is established by means of microscopy. 

 Illustrative of this technique is the testing of various ions. For 

 example, a solution containing copper and ammonium is so toxic that even 

 at a concentration of 0.05 mg/1 active from the living cells is practi- 

 cally absent, and at 0.5 mg/1 no cells survived (Table 1). 



TABLE 1. RESULTS OF THE TOXICITY OF A COPPER-AMMONIUM SOLUTION ON 

 TEST CULTURE OF MICROCYSTIS AERUGINOSA (LABORATORY STRAIN, 



5-DAY EXPERIMENT) 



Concentration Percentage' 



mg/1 Living Dead Dying 



Control 68 32 0.0 

 0.05 10.7 89.3 

 0.1 96.8 3.2 



0.5 100 



1.0 TOO 



103 



