Kiera Jefferson
Algae are a natural component of the aquatic food chain and are typically not harmful to people. However, certain types of algae produce toxins that can be harmful to humans, animals, and the environment. These toxins are stimulated by environmental factors such as light, temperature, salinity, pH, and nutrient levels. Algae can act as bioindicators, helping to identify and qualify the effects of pollutants on the environment. They are particularly effective at removing nutrients such as nitrogen and phosphorus, as well as harmful substances like heavy metals, pesticides, and organic and inorganic toxins. This is achieved by accumulating these substances within their cells. Algal blooms, or excessive algal growth, can be triggered by warmer water temperatures and excessive nutrients from fertilizers or sewage waste. These blooms can have detrimental effects on the environment, including depleting oxygen levels in the water, blocking sunlight, and causing illnesses in humans and animals.
| Characteristics | Values |
|---|---|
| Role | Removal of organic pollutants in water bodies |
| Pollutants Removed | Nitrates, ammonia, phosphates, nitrogen, phosphorus, heavy metals, pesticides, organic and inorganic toxins |
| Use | Indicator of water pollution, used to identify and qualify the effects of pollutants on the environment |
| Pollution Indicators | Algae growth, either rampant or stunted |
| Pollution Sources | Agricultural and urban runoff, sewage discharges, detergents containing phosphorus, manure, industrial processes that discharge organic waste |
| Pollutant Effects | Harmful algal blooms (HABs) that deplete oxygen in the water, block sunlight, and release toxins that harm people, animals, fish, and other parts of the ecosystem |
| Algae Types | Chlorophytes (green algae and flagellates), diatoms, cyanobacteria |
| Algae-Related Issues | Clogged screens of intake pipes from drinking water reservoirs, unpleasant taste and odor of water |
| Algae-Related Projects | Re-directing wastewater discharges, stormwater collection and retention improvements, sanitary sewer collection improvements, repairing or removing malfunctioning septic tanks |
| Algal Blooms Causes | Excess nutrients (nitrogen and phosphorus), warmer water temperatures, excessive nutrients from fertilizers or sewage waste |
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Nitrogen and phosphorus
Nitrogen is one of the important components for algae and is available in nature in various redox states. It influences the fatty acids profile of algae, with nitrogen limitation conditions resulting in higher saturated fatty acids. Natural manure or effluent may provide sufficient nitrogen to algae, and its availability can impact algal physiology and metabolism.
Phosphorus, in appropriate quantities, is used by vegetation and soil microbes for normal growth. It is a critical nutrient required for the formation of DNA, cellular energy, and cell membranes, including plant cell walls. Phosphorus is particularly important in the growth of algae, contributing to freshwater, coastal, and estuarine algal blooms.
Excessive amounts of phosphorus can lead to water quality issues, such as eutrophication and harmful algal growth. Harmful algal blooms (HABs) can cause serious health effects and even death. They can also damage the environment by depleting oxygen in the water, blocking sunlight from reaching deeper organisms, and releasing toxins that harm people, animals, fish, and other parts of the ecosystem.
The availability of nitrogen and phosphorus is crucial for algal growth and biomass production. They are essential macronutrients that regulate metabolic processes and influence lipid content and fatty acid production in algae.
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Heavy metals
Algae are always present in natural bodies of water, including salt water, fresh water, and brackish water. They are microscopic organisms that produce energy through photosynthesis, just like plants. While some types of algae produce toxins, they can also be used to capture and remove pollutants from water.
Algae, specifically microalgae, have been found to effectively capture and remove heavy metals from wastewater. This process is known as phycoremediation or bioremediation. Microalgae exhibit high resistance to heavy metals and possess self-defense mechanisms against their toxicity. They can remove heavy metals through different extracellular and intracellular mechanisms, including biosorption, bioaccumulation, and detoxification.
Non-living microalgae are particularly effective in absorbing heavy metal ions. Their absorption capacity is comparable to or even higher than that of living microalgae, and it can be enhanced through various chemical methods. Non-living algae have the advantage of reusability and are easier to control and optimize. They also do not require the addition of nutrients to the environment.
The use of algae in heavy metal remediation offers several benefits, including high absorption efficiency, availability, and cost-effectiveness. Algae have been investigated for their ability to remove heavy metals such as copper, aluminum, cadmium, zinc, mercury, chromium, nickel, and lead from aqueous solutions.
Overall, algae play a significant role in the sustainable removal of heavy metals from wastewater, contributing to the development of green technology in water management.
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Pesticides
Algae play an important role in the biological treatment of wastewater, known as "phycoremediation". They can accumulate organic and inorganic toxic substances, as well as radioactive materials, in their cells. This process, known as biosorption, is an ideal way to remove various pollutants, including pesticides.
Algae can absorb and accumulate pesticides, which affects the fate of these pollutants in marine ecosystems. This absorption can occur through active transport or diffusion, with the toxins entering the cells and accumulating in the algae's body. Different algae species have diverse physiologies, metabolic pathways, and susceptibilities to different toxicological processes, so the impact of pesticides on these species can vary significantly.
Specific species of algae may be more vulnerable to certain pesticides, while others may have built-in detoxification mechanisms. For example, herbicides can significantly impact the photosynthetic activity of algae, but some algae may react minimally or not at all to low doses of pesticides.
The use of algae-based metabolites as bio-pesticides is being explored as an alternative to synthetic pesticides, which have negative impacts on ecosystems. These natural products are safer for the environment and non-target organisms, and they are less likely to produce resistance due to their diverse mechanisms of action. Extensive research has been conducted on macro- and microalgal species, and a wide array of extracts and bioactive compounds with pesticidal action have been discovered.
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Organic toxins
Algae are always present in natural bodies of water, such as oceans, lakes, and rivers, and some types produce toxins. Toxin-producing algae can cause harmful algal blooms (HABs) when they grow excessively. HABs can cause serious health issues and even death for both humans and animals.
Algal blooms are triggered by environmental factors such as warmer water temperatures in the summer, light, and excessive nutrients from fertilisers or sewage waste brought by runoff. These blooms deplete oxygen in the water, which can kill fish and other living creatures. HABs that bloom near the water surface can also block sunlight from reaching organisms deeper in the water.
One example of a toxic algae is Alexandrium, which can lead to paralytic shellfish poisoning, resulting in paralysis and even death. Another example is Pseudo-nitzschia, which produces a toxin called domoic acid that causes vomiting, diarrhoea, confusion, seizures, and even death when consumed at high levels.
Cyanobacteria, also known as blue-green algae, are a common cause of water-quality concerns. They produce intracellular and extracellular metabolites, including biotoxins (such as microcystin and cylindrospermopsin) and taste-and-odour (T&O) compounds (such as 2-methylisoborneol and geosmin). These compounds can impact water supplies and cause economic and public health issues.
To treat algal toxins, methods such as using potassium permanganate, activated carbon, oxidation, chlorine, and ozone can be employed. Among these, the use of potassium permanganate at a concentration of 2 mg/l has proven to be the most effective while preserving the ecosystem.
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Inorganic toxins
While algae are usually present in natural bodies of water like oceans, lakes, and rivers, certain types of toxin-producing algae can be harmful. These harmful algal blooms (HABs) occur when toxin-producing algae grow excessively in a body of water due to environmental factors such as light, temperature, salinity, pH, and nutrient levels.
One example of an inorganic toxin is cyanobacteria, which are a type of blue-green algae commonly associated with harmful algal blooms. Cyanobacteria create toxic secondary metabolites that are harmful to various organisms. For instance, the cyanobacteria Microcystis, found in freshwater sources like the Great Lakes, produces a liver toxin that can cause gastrointestinal illness and liver damage. Another cyanotoxin, guanitoxin, can affect the nervous system of humans and other organisms.
The presence of high levels of nutrients, particularly nitrogen and phosphorus, from sources such as fertilizers and sewage waste, can contribute to the growth of algae and the formation of HABs. These HABs deplete oxygen levels in the water, creating dead zones where aquatic life cannot survive. Additionally, the toxins released by HABs can contaminate drinking water, causing illnesses and even death in humans and animals.
It is important to address the sources of pollution and implement effective treatment methods, such as establishing wetlands, to reduce the occurrence of harmful algal blooms and mitigate their impact on the environment and public health.
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Frequently asked questions
Algae can capture excess nutrients, such as nitrogen and phosphorus, that enter waterways from sources like industrial and wastewater treatment plants, septic tanks, stormwater runoff, and nutrient-enriched rainfall. Algae also remove harmful substances like heavy metals, pesticides, and organic and inorganic toxins from the water.
Algae capture pollutants by accumulating them within their cells. Algae have a high demand for certain nutrients, such as nitrogen and phosphorus, and can absorb large quantities of these chemicals from the water within hours.
Algae play a crucial role in maintaining water quality and ecosystem health. By capturing excess nutrients and pollutants, algae help prevent algal blooms, which can be harmful to the environment and human health.
Microscopic analysis of water samples can determine the types and concentrations of pollutants that algae have captured. Additionally, algae can be used as bioindicators to identify and qualify the effects of pollutants on the environment and provide information about the cumulative impact of various water pollutants.
