Pollution's Impact: Algae Under Threat

Algae are primary producers in aquatic ecosystems and play a significant role in water pollution. They are often unicellular and, as such, are in constant contact with their environment, absorbing nutrients necessary for growth and photosynthesis. This also means that pollutants can easily enter their cells and accumulate, affecting their growth and shape.

One of the most important environmental problems today is the pollution of surface water, which can lead to high organic content in aquatic ecosystems and eutrophication. Eutrophication is the increase in plant nutrients and biota in a watercourse, often caused by farming and sewage effluent. This can lead to algal blooms, which deplete oxygen in the water, causing the death of other organisms.

Algae are also affected by heavy metals and organochlorine compounds, which can inhibit their growth and cell division. They can also be used as bioindicators to identify and qualify the effects of pollutants on the environment.

Additionally, algae play a role in the self-purification of water bodies and can be used in wastewater treatment, as they can accumulate and remove nutrients, heavy metals, pesticides, and radioactive matters from surrounding water.

Heavy metals can cause algae to change shape

Heavy metals are metallic elements with densities greater than 5 g/cm^3. They are toxic to algae even at low concentrations. Heavy metals can enter algal cells as they acquire nutrients necessary for growth and photosynthesis. Heavy metals can cause oxidative stress in algae, which can lead to lipid peroxidation, DNA damage, and altered cell structure.

Algae can accumulate heavy metals through various mechanisms, including biosorption, bioaccumulation, and biotransformation. Biosorption is a rapid process where heavy metal ions are passively absorbed by living and non-living biomass. Bioaccumulation is a slow, intracellular process where heavy metals are transported across the cell membrane. Biotransformation involves the enzymatic and biochemical conversion of heavy metals into less harmful forms.

Algae can also immobilise heavy metals through various techniques, such as adsorption, encapsulation, entrapment, and self-immobilisation. Immobilisation can enhance the stability of heavy metal adsorption by algae.

The response of algae to heavy metals depends on various factors, including the type and concentration of the heavy metal, the growth stage of the algae, and the place from which the algae were isolated.

Organic pollution can cause algal blooms

Organic pollution is a large and long-lasting pollution threat that can be recognised at the global level. It occurs when large quantities of organic compounds from many sources are released into bodies of water. Organic pollution can cause eutrophication, which is when there is a high organic content in aquatic ecosystems. Eutrophication can reduce water quality, thus restricting the use of water bodies for many purposes.

Organic pollution can negatively affect water quality in several ways. During the decomposition process of organic water, dissolved oxygen in the water may be used up at a greater rate than it can be replenished, resulting in oxygen depletion, which causes severe consequences for aquatic life. Organic effluents also frequently contain large quantities of suspended solids, which reduce the amount of light available to photosynthetic organisms, mainly algae.

Organic pollution can cause an increase in the density of algae in an aquatic system, known as an algal bloom. While algal blooms sometimes occur naturally, their frequency, duration and intensity are increased by nutrient pollution. Algae can multiply quickly in waterways with an overabundance of nitrogen and phosphorus, particularly when the water is warm and the weather is calm. This proliferation causes blooms of algae that turn the water noticeably green, although other colours can occur.

Excess nitrogen and phosphorus cause an overgrowth of algae in a short period of time, also called an algae bloom. The overgrowth of algae consumes oxygen and blocks sunlight from underwater plants. When the algae eventually die, they deplete the oxygen in the water, making it impossible for aquatic life to survive. This results in what is known as a dead zone. The largest dead zone in the United States, about 6,500 square miles, is in the Gulf of Mexico and occurs every summer as a result of nutrient pollution from the Mississippi River Basin.

Algae can be used to treat wastewater

The harvested biomass can be used for several purposes, including:

• Animal feed
• Biofuel production
• Biofertilizer
• Biodiesel production
• Nitrogen and phosphorus removal from wastewater
• Inhibition of coliforms
• Removal of heavy metals

Algae-based wastewater treatment has several benefits, including:

• Cost-effectiveness
• Low energy requirements
• Reduction in sludge formation
• Greenhouse gas emissions reduction

However, there are also some challenges associated with algae-based wastewater treatment, such as:

• Pre-treatment of wastewater to remove bacteria, protozoa, and other organisms that may inhibit algae growth
• Selection of suitable algae strains that are robust enough to handle fluctuations in environmental factors
• Harvesting of algae from wastewater, which can be energy-intensive and challenging due to the small size of algae cells
• Internal shading, which can limit the photosynthetic activity of algae
• Suspended solids and turbidity of the wastewater, which can interfere with algae growth and photosynthesis

Algae can be toxic to humans and animals

Symptoms of exposure depend on the type of algae and the extent of exposure. For example, cyanobacteria (blue-green algae) are the most common cause of harmful algal blooms in freshwater, while dinoflagellates and diatoms are the primary causes of blooms in saltwater. It is important to note that not all algae produce toxins, and not all blooms are harmful.

To protect humans and animals from the toxic effects of harmful algal blooms, it is crucial to follow safety guidelines. People should avoid swimming or engaging in water sports in affected waters and keep children and pets away from these areas. It is also essential to follow advisories and warnings from local officials and avoid water that appears discoloured, has scum, or smells bad.

In the event of exposure to harmful algae, immediate action should be taken. Rinsing with clean water is recommended for both humans and animals to remove any traces of algae. If illness occurs, seeking medical advice is crucial, with specific hotlines available for human and animal health concerns.

Algae can be used as bioindicators of pollution

Algae are the main primary producers in all kinds of water bodies and are involved in water pollution in significant ways. Enrichments of algal nutrients in water through organic effluents may stimulate the growth of certain algal species, resulting in massive surface growths or 'blooms' that reduce water quality. However, certain algae that flourish in water polluted with organic waste play an important part in the "self-purification of water bodies".

Algae can also be used to indicate the presence of clean water, as many species occur predominantly in the clean water zone of streams. The presence or absence of several species of clean water algae can be a better indicator of water quality than any single species.

Algae are also used in wastewater treatment. They are able to accumulate plant nutrients, heavy metals, pesticides, organic and inorganic toxic substances, and radioactive matter in their cells. They can remove nutrients, particularly nitrogen and phosphorus, from wastewater. They can also be used to remove biogenic elements, polychlorinated biphenyls, and heavy metals during the biological final treatment of wastewaters.

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