In the framework of project “Harnessing Algae Power for Pollution Reduction and Blue Growth” (project acronym – AlgaeRevive, project code – BSB00091) within the framework of the (Interreg VI-B) NEXT Black Sea Basin Programme, financed by the European Union OSAU has completed an experimental investigation comparing the cultivation conditions of Chlorella microalgae in artificial bioreactors with those in natural regional water bodies.
About the Research
The study was conducted from late June to mid-August 2025. Scientists analyzed physicochemical parameters of water from Lake Yalpug and the Black Sea, comparing them with nutrient medium indicators under laboratory conditions.
Microalgae serve as important bioindicators of aquatic ecosystem health. Their growth depends on numerous factors: lighting, temperature, water chemical composition, and oxygen and carbon dioxide concentrations. Understanding these parameters enables prediction of growth activity changes in various microalgae species.
Methodology
Water samples were collected from Lake Yalpug on June 27 and August 8, and from the Black Sea coast near Odesa on August 11-13, 2025. Key parameters were determined for each sample: pH, oxidation-reduction potential, electrical conductivity, total mineralization, temperature, oxygen content, and water turbidity.
Concurrently, Chlorella cultivation was performed in 30-liter glass bioreactors using a commercial culture from BioGreen private enterprise (Bila Tserkva). Artificial lighting at 15W power provided stable growth conditions.
Key Findings
The research revealed substantial differences between natural water bodies and artificial nutrient medium:
pH levels: Natural reservoirs exhibited alkaline reactions (8.8-9.5), while the culture medium maintained a slightly acidic pH (6.4-6.7), optimal for Chlorella growth.
Mineralization: Lake Yalpug showed the highest salinity and total mineralization values — 14-200 times higher than the artificial medium. Black Sea water had intermediate indicators — 3-5 times higher than the culture medium.
Electrical conductivity: This parameter correlated with mineralization levels, demonstrating the highest values in Lake Yalpug (1387-1478 μS/cm).
Dissolved oxygen: Maximum concentration (9.4 mg/L) was observed in the nutrient medium at cultivation onset, while the lowest (5.5 mg/L) was in seawater.
Turbidity: The artificial medium at peak Chlorella biomass reached 610 units, while seawater transparency remained high (2 units).
Conclusions and Practical Significance
Scientists attribute Lake Yalpug’s high mineralization to its natural characteristics as a highly saline water body. Lack of precipitation before late June led to increased salinity, while intensive July rainfall somewhat diluted the water, as reflected in August samples.
High salinity and mineralization levels make these natural water bodies poorly suitable or completely unsuitable for Chlorella cultivation. Extended periods without precipitation can lead to partial lake desiccation and activation of halophilic microflora. Conversely, abundant rainfall can dilute seawater, provoking intensive blooms of green unicellular algae.
During seawater sampling, no significant precipitation was observed, resulting in relatively high mineralization levels and low water temperature (22°C), which did not favor unicellular algae reproduction.
The research findings hold significant importance for understanding optimal conditions for industrial microalgae cultivation and assessing the ecological status of regional natural water bodies.
Detailed Physicochemical Water Parameters
| Sample Source | pH | ORP, mV | Conductivity, μS/cm | TDS, mg/L | Salinity, mg/L | DO, mg/L | Turbidity, units | Temperature, °C |
| Lake Yalpug (June 27) | 9.5±0.03 | 110.3±2 | 1478±5.6 | 975±7.6 | 704±10 | 7.3±0.1 | 74.4±6.2 | 29.7±0.2 |
| Lake Yalpug (August 8) | 8.8±0.01 | 63.8±0.8 | 1387±6.2 | 920±2.4 | 680±8.2 | 7.0±0.2 | 73.9±6.3 | 25.5±0.1 |
| Black Sea (August 11-13) | 8.8±0.003 | 66.7±0.7 | 25.3±0.09 | 16.6±0.03 | 15.6±0.03 | 5.5±0.25 | 2.0±0.003 | 22.1±0.08 |
| Nutrient medium (start) | 6.41±0.01 | 67.1±1 | 7.21±0.03 | 4.75±0.005 | 3.95±0.006 | 9.4±0.3 | 4.63±0.04 | 30.6±0.1 |
| Nutrient medium (end) | 6.7±0.02 | 51.9±0.5 | 9.9±0.02 | 6.52±0.005 | 5.61±0.004 | 7.4±0.3 | 610±28 | 31.3±0.1 |
Note: ORP — oxidation-reduction potential; TDS — total dissolved solids; DO — dissolved oxygen
The project is being implemented between September 3, 2024, and March 2, 2027, and has a total value of €1470899.04 of which €1329809.13 is funding provided by the European Union through the (Interreg VI-B) NEXT Black Sea Basin Programme. As a partner, Odesa State Agrarian University partner eligible budget is €219564,00.
“Harnessing Algae Power for Pollution Reduction and Blue Growth
Odesa State Agrarian University
https://osau.edu.ua/en
osau@osau.edu.ua
Publishing date October 08, 2025
The responsibility for the content of this material is that of the author(s). The content of this material does not necessarily represent the official position of the European Union. Reproduction is authorized, provided the source is acknowledged, and any changes are indicated”
