How algae help clean oil from petroleum. KELP FARMS presents experiment results

Problem relevance

The Black Sea disaster in December 2024, when two tankers lost large volumes of fuel oil as a result of a storm, led to the contamination of vast marine areas and caused severe damage to marine ecosystems due to petroleum pollution.

According to Oil Tanker Spill Statistics, six major spills (>700 tonnes) and four medium spills (7-700 tonnes) resulting from tanker incidents were recorded in 2024. The major spills primarily involved fuel oil and occurred in South America, Asia, and Europe. The total volume of oil released into the environment from tanker spills in 2024 was approximately 10,000 tonnes.

The scale of the impact of oil pollution on marine ecosystems is staggering: just one ton of oil spilled on the water surface creates a film covering an area of ​​12 square kilometers. This film blocks oxygen from entering the water, disrupts gas exchange with the atmosphere, and creates critical conditions for marine organisms.

Natural self-cleaning mechanisms

Nature has developed its own mechanisms to combat hydrocarbon pollution. The oceans are home to so-called oil-oxidizing microorganisms, capable of breaking down petroleum hydrocarbons and converting them into less toxic compounds. However, the intensity of modern pollution often exceeds the natural capabilities of these microorganisms.

Seaweed plays a key role in these processes. Scientists have long observed that algal beds can trap oil spills, acting as natural containment booms, and participate in the biological processing of pollution.

Studying the Black Sea Cystoseira

KELP FARMS conducted a detailed study of the ability of the brown alga Cystoseira barbata to resist oil pollution. Cystoseira was chosen deliberately – it is one of the most common macrophyte species in the Black Sea, forming extensive underwater forests in the coastal zone.

The experiment used actual samples of M-100 fuel oil collected on the Black Sea coast after the December 2024 disaster. The researchers created experimental conditions as close to real conditions as possible: seawater with a salinity of 19 ppm, a temperature of 20-26°C, continuous aeration, and lighting.

Experimental methodology

A mixture of sand and fuel oil was soaked in seawater for a week at 26°C to obtain a concentrated solution of oil fractions. Cystoseira branches weighing 10 to 19 grams were then added to the experimental containers. The control group was maintained in clean seawater with nutrients.

Every 10-11 days, the researchers collected water samples for gas chromatography analysis of oil product content. At the end of the month-long experiment, algal tissue and surface contaminants were also analyzed.

Study results

The obtained data were quite impressive. The initial concentration of dissolved petroleum products in the experimental water was 6.5-7.1 mg/L, exceeding the maximum permissible concentrations for seawater by 130-140 times. These conditions can be classified as «acute» toxicological.

During the first 11 days, the concentration of petroleum products remained virtually unchanged, due to the continued influx of dissolved fractions from the fuel oil. However, noticeable changes then began. On day 21, the concentration dropped to 2.24 mg/L (a 72% decrease from the initial values). On day 31, it dropped to 0.95 mg/L (an 81% decrease).

The total bioremediation volume amounted to approximately 52.65 mg of petroleum products over the entire experimental period. The most intensive purification processes occurred from days 11 to 21.

Accumulation of contaminants in algae tissue

From the results of the experiment, based on 1 kg of wet weight of Black Sea Cystoseira, it follows that the content of petroleum hydrocarbons in the surface pollution of algae is on average 11318 mg/kg of wet weight, the content of petroleum hydrocarbons in the tissues of algae is mg/kg of wet weight — 898 mg/kg of wet weight, which is approximately 8% of the amount of hydrocarbons in the surface pollution.

Thus, the resistance of Cystoseira to high concentrations of M-100 fuel oil, its ability to deposit significant quantities of toxic substances on its surface, and also to accumulate them in tissues was demonstrated.

Impact on the algae themselves

High concentrations of petroleum products had a noticeable impact on the condition of Cystoseira. After 11 days, a change in the algae’s color was observed – a darkening caused by the precipitation of colored fractions of the fuel oil. On the 21st day, structural damage began, manifested by fragmentation of the thalli.

Under control conditions (clean seawater), the algae showed a 14-35% increase in biomass, while under oil-polluted conditions, a weight loss of 12.8-39.1% was observed.

Mechanisms of interaction between algae and petroleum products

Physicochemical processes

The surface of algae cells consists of various functional groups—carboxyl and sulfate groups, as well as proteins, lipids, and polysaccharides. These components are capable of interacting with the hydrophobic molecules of petroleum hydrocarbons, ensuring their adsorption.

Brown algae contain alginate, which has good biosorption capacity.

Carbohydrates make up approximately 16% of the biomass of brown algae, which facilitates the effective binding of contaminants.

Biological mechanisms

The symbiosis between algae and oil-oxidizing bacteria plays a key role in petroleum refining. The developed surface of the algae serves as a substrate for specialized microorganisms that oxidize hydrocarbons and convert them into forms accessible to the algae.

The algae, in turn, provide the bacteria with oxygen during photosynthesis, increasing their oxidative activity. Some studies indicate that this symbiosis has a higher potential for the degradation of petroleum hydrocarbons.

Metabolic integration

Surprisingly, algae are able to incorporate some petroleum hydrocarbons into their metabolism. This explains why low concentrations of petroleum products can even stimulate the growth of some algae species. Metals contained in petroleum products (iron, manganese, and nickel), acting as micronutrients, also play a role.

Comparison with international data

The results obtained are in good agreement with international studies on the effectiveness of seaweeds in bioremediation. The specific bioremediation rate of Black Sea Cystoseira under the conditions of this toxicology experiment was 93.6-141.94 mcg/g/day, which is comparable to values ​​for northern brown algae species in the Barents Sea (44.0-202.0 mcg/g/day).

For comparison, the brown algae Macrocystis pyrifera off the coast of Mexico is capable of extracting up to 112,000 mcg of gasoline per gram of dry weight from seawater, while Saccharina latissima in northern seas accumulates up to 10,740 mcg of petroleum products per gram.

Practical significance of the results

Natural bioremediation

The study results confirm the important role of natural algal communities in maintaining the ecological balance of coastal zones. According to the scientists’ calculations, one square meter of algal growth is capable of neutralizing the film formed by a 100 ml oil spill in this area within 4-5 days.

Prospects for technological application

The study opens up prospects for the creation of artificial biological treatment systems. It is proposed to use Cystoseira «booms» to combat fresh oil spills. This approach combines environmental safety with high efficiency.

A significant advantage of algae as biosorbents is their availability and renewable nature. Unlike artificial sorbents, algae do not require complex technological processing and can be effectively used even in dried form.

Ecosystem importance

These findings highlight the critical importance of preserving natural algal communities. Destroying even a portion of these communities can disrupt the natural self-purification mechanisms of marine ecosystems and reduce their resilience to anthropogenic pollution.

Limitations and research prospects

Despite the encouraging results, the study has certain limitations. The experiment was conducted in laboratory conditions with a limited water volume and controlled environmental parameters. Under natural conditions, bioremediation efficiency can be affected by currents, waves, temperature fluctuations, and other factors.

Long-term exposure to high concentrations of oil products (more than 10-11 days) resulted in the degradation and death of algae, limiting their use in large spills.

Further research is needed to study:

• Species-specific sorption properties of different algae

• Optimal conditions for the functioning of biosanitary plantations

• Long-term consequences of oil product accumulation in marine ecosystems

• Technologies for scaling up biological treatment methods

• Recycling of algae used for biosanitary purposes

Conclusion

The KELP FARMS study has provided the first detailed insight into the mechanisms and effectiveness of Black Sea Cystoseira in the bioremediation of oil spills. The data obtained confirm the high potential of seaweeds as natural biofilters and open up prospects for the development of environmentally friendly technologies for oil spill response.

These results are particularly relevant in light of the recent environmental disaster in the Black Sea and highlight the need for a comprehensive approach to protecting marine ecosystems, including both pollution prevention and maintaining natural self-purification mechanisms.

Algal communities are not only an important component of marine ecosystems but also a potential tool for environmental protection. Their conservation and study should be a priority in modern marine ecology and environmental policy.