Balancing diets of farm animals and poultry on the content of mineral elements is a necessary for proper functioning of the body, active growth and development, reproduction and production. One of these trace elements necessary for the body is iodine, which is mainly concentrated in the thyroid gland. The biological role of iodine is associated with the synthesis of thyroid hormones, which conduct humoral regulation of many physiological functions, control the growth and differentiation of tissues, affect on the rate of metabolism in the body, metabolism of vitamins, water and many electrolytes.

In plant feed iodine is contained in small amounts, animal feed, including fish meal that contains more minerals. Marine and freshwater algae are also rich in iodine, but it’s assimilation from these components in the body of animals and birds depends on several factors, among which is the balance of macro elements in feed rations.

In plant and animal organisms assimilation of iodine depends on its antagonistic or synergistic interactions with other chemical elements and their compounds. Increasing iodine content in biological objects can reduce or increase the assimilation of trace elements.

The basis for the prevention of endemic goiter is iodine deficiency compensation. The most natural and effective is the inclusion in the diet of marine and freshwater algae that contain organic iodine compounds, and also have a unique feature to accumulate it from the nutrient environment. In addition, algae biomass has nutritional value, contains complete protein and a full set of nonessential and essential amino-acids that contribute to a better absorption of iodine in the body.

Freshwater alga Lemna Minor like all algae has a good ability to accumulate from water minerals and this property can be used for enrichment with iodine. However, algae can accumulate and other minerals from water environment, and so it is necessary to study macro element content of biomass and its dynamics by introducing various doses of iodine in the nutrient environment for growing algae.

The objective of the research was to study the composition of macro element content of freshwater algae Lemna Minor, establish the influence of different doses of Iodine in nutrient environment on dynamics of macro elements (cations): Potassium, Sodium, Magnesium, Calcium, and anions: chlorides, sulfates, phosphates, nitrates in its biomass.

For the research it was made nutrient environments with introduction of 40, 260, 380, 500, 1000 mg/dm³ Iodine, during 30 days cultivation of freshwater algae Lemna Minor taken from the natural environment was conducted. In the control nutrient environment Iodine was not added. At the end of the experiment in the dried biomass of algae content of cations was conducted: Potassium, Sodium, Magnesium, Calcium, and anions: chlorides, sulfates, phosphates, nitrates by capillary electrophoresis according to working instructions, based on the methods the company of "Lumex".

To prepare the control solution of cations and anions standard samples of the company "ICN", USA were used.

Using 500 mg/dm³ Iodine Potassium content in dry matter of Lemna Minor prevailed control data at 0.47 % (р<0.05). Increasing Iodine content in nutrient environment to 1000 mg/dm³ conduced to accumulation of Potassium in the biomass of algae. The content of the element was higher than in control on 1.04 %. The difference had reliable nature.

Adding to the nutrient environment 260–500 mg/dm³ of Iodine led to a tendency to reduce Sodium content in the biomass of Lemna Minor. The use of high doses of Iodine – 1000 mg/dm³ accompanied by a reliable decrease in the concentration of Sodium in the algae biomass. The difference from the control was 0.1 %.

Increasing Iodine content in the nutrient environment from 260 to 1000 mg/dm³ led to a decrease in Magnesium content in biomass LemnaMinor on 0,2 % (р<0.01) – 0.22 % (р<0.001).

It was found that doses of Iodine 260 and 380 mg/dm³ most stimulated Calcium accumulation in biomass of Lemna Minor. The concentration of element was higher compared to control, respectively, 1.24 and 1.36 % (р<0.01).

In biomass from control variant Chloride content was at 1.12 %. This indicator was not detected of Iodine exposure in dose of 40 mg/dm³. Regularity was established: with increasing Iodine content in the nutrient environment chlorides content in the biomass of Lemna Minor reduced. Using nutrient environments  containing Iodine 380, 500 and 1000 mg/dm³ in algae biomass chloride content decreased, respectively, on 0.19 % (р<0.01), 0.47 (р<0.001) та 0.69 % (р<0.001).

It was proved that with increasing Iodine content in nutrient environment concentration of nitrates in biomass of Lemna Minor reduced. Using Iodine in the doses of 40, 260, 380 and 500 mg/dm³ it is tendency to reduce nitrate levels. Using Iodine in the doses of 1000 mg/dm³ nitrate content in algae biomass decreased on 0.03 % (р<0.05).

The use of 260 mg/dm³ of Iodine in the nutrient environment resulted in increase of phosphates in biomass of LemnaMinor on 0.03 %. At high doses of Iodine – 380, 500 and 1000 mg/dm³ concentration of phosphates in algae biomass increased in 7,0 and 9, 25 times.

The most stimulating dose of Iodine that resulted sulfates accumulation in Lemma Minor biomass was 40 mg/dm³. In this variant sulfates concentration was higher than in control on 0.83 % (р<0.001).

Key words: biomass of alga LemnaMinor, nutrient environment, Potassium, Sodium, Magnesium, Calcium, chlorides, sulfates, phosphates, nitrates.