For the purpose of controlling the quantity of plankton organisms in in- 

 dustrial water supplies, we tested another c lass--organostannic compounds 

 and trialkyl/aryl/substituted compounds in particular, which possess fun- 

 gicidal and insecticidal properties. We tested trimethylstannano 1 and trim- 

 ethyl acetoxy-stannane which strongly suppressed the vital functions of 

 algae even at a concentration of 0.^ mg/liter. In the same concentrations, 

 these compounds suppressed the reproduction process in representatives of 

 zooplankton. The advantage of organostannic compounds over other algicides 

 is that they are toxic for plankton organisms at considerably lower concen- 

 trations . 



However, it is important to use 

 to the undesirable algae. Often bl 

 the development of zooplankton and 

 toxicity tests with silicone compou 

 si lane, trif luoropropinyldiethoxysi 

 mg/liter depresses the number of al 

 of the test; however, in the subseq 

 creases slightly and reaches 50% of 

 Mollusca showed 100% survival even 

 The number of young borne by Daphni 

 in the control . 



substances that 

 ooms must be supp 

 other aquatic org 

 nds (vinyl -trieth 

 lane, and others 

 gae by roughly 94 

 uent 15 days the 



the control . Te 

 at 1 mg/liter of 

 a in the test pro 



are selectively toxic 

 ressed without harming 

 anisms. Phytoplankton 

 oxysilane, tetraethoxy- 

 showed that 0.01 

 96% in the first days 

 number of cells in- 

 sts on Daphni a and 

 silicone compounds, 

 ved to be greater than 



By comparison of the sensitivity of representatives of zoo- and phyto- 

 plankton to silicone compounds, the high selectivity of phytoplankton is re- 

 vealed, as well as low sensitivity or stimulation of Daphni a . The ability 

 of silicone compounds to reduce algae cells can be utilized to suppress the 

 development of phytoplankton during blooms. 



Alkoxysilanes have the advantage over previously-used algicides to com- 

 bat blooms because they are comparatively quickly destroyed in water and 

 have a selective effect on phytoplankton, while not suppressing the vital 

 activity of Daphni a and Mollusca . 



The development and utilization of toxic substances, which possess a 

 narrow selective effect, opens a path towards the synthesis of substances 

 with prescribed toxicity for certain aquatic organisms and is the basis for 

 the development of the best methods of controlling the number of zoo- and 

 phytoplankton in reservoirs. 



No one method is best and there should be several such methods for spe- 

 cific purposes for each water body. 



REFERENCES 



Terent'ev, A. P., Stroganov, N.S., Rukhadze, Ye. G., Khobot'ev, V.G. DAN 

 SSR , 164(4) (1965). 



Stroganov, N.S., Kochkin, D.A. Khobot'ev, V.G., Kolosova, L.V. DAN SSSR , 

 170(5) (1966). 



85 



