Impact Of Pollution On Euglena Population Growth

Euglena, a unicellular marine algae, is often used in experiments to study the effects of anthropogenic factors on test objects. Due to its short life cycle, it is an ideal candidate for investigations into the impact of environmental pollution on population growth. This is especially important given the increasing stress on freshwater sources due to rising populations, urbanization, industrialization, and high water consumption in agriculture and industry.

Heavy metals

Heavy metal pollution is a pressing issue, as these inorganic pollutants are increasingly being discarded into our waters, soils, and atmosphere due to the rapidly growing agriculture and metal industries, as well as improper waste disposal. Heavy metals can affect biological functions and growth and can accumulate in organs, causing serious diseases such as cancer.

The flagellate *Euglena proxima*, isolated from industrial wastewater, has shown tolerance against Cr6+ and Pb2+. The metal ions slowed down the growth of the organism after 4–5 days of exposure, with a reduction in the cell population of 68% for Cr6+ and 59% for Pb2+ after 8 days. The reduction in the amount of Cr6+ after 7, 14, and 21 days of flagellate culturing was 76%, 80%, and 88%, respectively, while *Euglena proxima* could also remove 78% Pb2+ after 7 days, 82% after 14 days, and 90% after 21 days from the culture medium. The acid digestion of *Euglena proxima* showed 84% of Cr6+ and 88% of Pb2+ ions accumulated in the organism. The heavy metal uptake ability of *Euglena proxima* can be used for metal detoxification and environmental clean-up operations.

• Euglena gracilis has emerged as a novel and effective tool for the bioremediation of heavy metals, including cadmium. It can survive in harsh environments, such as those that are acidic (pH 2.5–7) and contain high concentrations of heavy metals. It is capable of absorbing heavy metals, including copper, lead, mercury, and cadmium, and has demonstrated greater absorption capabilities than other bioremediation organisms.
• Euglena mutabilis is an extremophilic species often found in highly toxic environments, including acid mine drainage. It is believed that its ability to form biofilms with other microorganisms strengthens its tolerance to extreme environments. The Cd tolerance of an Euglena mutabilis fungal-algal-bacterial (FAB) consortium was investigated, and it was found that suppressing the growth of the associated organisms through the use of antibiotic and antimycotic agents resulted in decreased Cd tolerance.

In summary, *Euglena* species have shown tolerance to heavy metals and can be used in bioremediation. *Euglena proxima* has been observed to have the ability to remove heavy metals from its environment, while *Euglena gracilis* has demonstrated greater absorption capabilities than other bioremediation organisms. *Euglena mutabilis* has also shown heavy metal tolerance, although the presence of associated organisms in its consortium may influence its response to heavy metal exposure.

Organic and inorganic pollutants

Inorganic pollutants include heavy metals, halides, oxyanions, cations, and radioactive materials. These substances can have serious health effects on humans, including abnormal growth, a higher risk of cancer, diabetes, and obesity. They may also persist longer in aquatic systems, further degrading water quality.

Organic pollutants, on the other hand, include petroleum hydrocarbons, volatile organic compounds, and per- and polyfluoroalkyl substances. These substances can also have toxic effects on the environment and human health.

The presence of both organic and inorganic pollutants in water can negatively impact the population growth of Euglena gracilis, a species of freshwater motile flagellate commonly used in ecotoxicological studies. E. gracilis is sensitive to various toxic substances, including heavy metals and inorganic and organic compounds. Its gravitactic orientation, which it uses to orient itself in the water column, can be impaired by these pollutants, making it a useful indicator organism for assessing water quality.

Increased salinity

Euglena gracilis, a species of freshwater flagellate, is often used in ecotoxicological studies to assess water pollution. This is due to its sensitivity to external stressors, which can affect its gravitactic and phototactic orientation. One such stressor is increased salinity.

Salinity refers to the concentration of salts dissolved in a body of water. When the salinity of a freshwater ecosystem increases, it can have significant effects on the organisms living there, including Euglena. Euglena gracilis, in particular, has been found to be sensitive to changes in salinity.

Moreover, elevated salinity levels can alter the density of the water, which plays a crucial role in the gravitactic orientation of Euglena. This organism uses gravity and light cues to position itself optimally within the water column for growth and reproduction. By disrupting the water density, increased salinity can interfere with Euglena's ability to orient itself properly, impacting its access to resources and potential for growth.

In addition to the direct effects on Euglena, increased salinity can also influence the availability and toxicity of other pollutants. For instance, heavy metals, such as cadmium and lead, may interact with salts in the water, leading to increased metal toxicity. This, in turn, can further exacerbate the negative impacts on Euglena populations, as heavy metals have been shown to impair their cellular and photosynthetic processes.

Ultraviolet radiation

Effects of UV on Photosynthesis and Respiration

UV radiation inhibits the photosynthetic rate and "light-enhanced dark respiration" (LEDR) in E. gracilis. LEDR is the maximum rate of oxygen consumption after a period of light minus the rate of oxygen consumption 30 seconds after the maximum rate. After 20 and 40 minutes of exposure to UV radiation, the photosynthetic rate and LEDR are reduced. At higher photon fluence rates, photosynthesis is lower than the control values. The inhibitory effects of UV radiation are greater after 40 minutes of exposure compared to 20 minutes.

Effects of UV on Chloroplast Development

UV radiation has been found to affect chloroplast development in E. gracilis. Chloroplasts are essential to photosynthesis, and their development can be inhibited by UV radiation.

Effects of UV on DNA Metabolism

UV radiation has been found to affect DNA metabolism in E. gracilis. This could have a range of effects on the cell, including impairing its ability to divide and reproduce.

Effects of UV on Cell Composition

UV radiation affects the cell composition of E. gracilis. For example, light is important for the production of vitamin E and phytol in E. gracilis. The presence of light also affects the fatty acid composition of E. gracilis cells, with higher amounts of unsaturated fatty acids produced in the presence of light.

Industrial effluent

Industrial activities are a major source of pressure on the environment, particularly in the form of emissions to the atmosphere and water ecosystems, waste generation, and resource consumption. Releases of pollutants by European industry have generally decreased over the last decade, but the impacts and costs of pollution remain high.

Heavy metals, such as mercury, lead, and cadmium, are among the pollutants found in industrial effluents, and these metals do not easily dissolve or disintegrate in the environment, persisting for long periods and causing pollution. Other pollutants found in industrial effluents include toxic chemicals, pesticides, and organic compounds.

The presence of these pollutants in water bodies can have severe consequences for aquatic ecosystems and biodiversity. They can alter breeding cycles, reduce light penetration for photosynthetic organisms, and cause toxic effects on aquatic life, leading to mass deaths of fish and other organisms.

The costs of air pollution caused by Europe's largest industrial plants are substantial, averaging between EUR 268 billion and EUR 428 billion per year. These costs correspond to about 2% of the EU's GDP, with just 1% of the most polluting industrial facilities causing half of the total damage.

To comply with stringent regulatory requirements, approved analytical methods exist for monitoring conventional pollutants in industrial effluents. However, due to the complexity of the sample matrix, modifications in instrumentation, sampling, and sample preparation techniques are often necessary.

Microalgae, such as Euglena gracilis, have gained attention for their potential in wastewater treatment. E. gracilis can rapidly remove biogenic elements that contribute to the eutrophication of water bodies. It can reduce the concentration of phosphorus and nitrogen in wastewater to the levels recommended by EU legislation.

In summary, industrial effluents pose a significant threat to the environment and human health due to the presence of various pollutants, including heavy metals and toxic chemicals. The costs of pollution from industrial activities are substantial, and while emissions have decreased, the impacts remain high. Microalgae like E. gracilis show promise in treating wastewater and reducing pollution levels.

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