The effect of water salinity on the toxicity of oil assessed by biotesting

The article is devoted to the analysis of the toxicity of the water fraction of oil formed in solutions of 13 and 35 g/l, using the biotesting method. From the solution of dehydrated oil from the Korchagin deposit at a concentration of 50 ml per liter of medium based on 13 and 35 g/l aqueous solutions of NaCl, the aqueous phase was selected one and two days after the addition of oil. The fluorimetric method was determined the content of hydrocarbons, which was 0.53 mg/l after 24 hours incubation and 1.07 mg/l after 48 hours incubation in the 13 g/l solution and 2.29 and 0.78 mg/l in the 35 g/l solution accordingly. The test object was the Artemia salina crustacean at the nauplii stage (2 days after hatching). The nauplii were counted 24 and 48 hours after being placed in a medium containing hydrocarbons. It was found that the output of nauplii from cysts is higher in an incubation medium with a mineralization of 35 g/l – 60 individuals per 10 ml of medium against 27 at 13 g/l, but the survival rate after 24 and 48 hours of the experiment (3 and 4 days after the exit from cysts) is lower by 43%. The biotesting data were well consistent with the results of chemical analysis. Higher concentrations of hydrocarbons in the incubation medium correspond to the highest mortality of test objects, and the toxic effect is higher the longer the nauplii are exposed to the toxicants. A. salina sensitivity to hydrocarbon concentrations in water and its tolerance to mineralization of 13 g/l make it a promising test object for testing the waters of the Northern Caspian Sea in the event of oil pollution.