How Pollution Breeds Blue-Green Algae Explosions

Blue-green algae, also known as cyanobacteria, are photosynthetic bacteria that are usually present in water bodies. They are known to cause harmful algal blooms (HABs) in aquatic ecosystems, which can have detrimental effects on human, livestock, and pet health. While HABs occur naturally, human activities such as nutrient pollution from excess nitrogen and phosphorus can increase their frequency and toxicity. These blooms can cause water discolouration, produce floating scums, and deplete oxygen levels in the water, leading to the death of aquatic life. Additionally, the toxins produced by blue-green algae can be harmful to humans and animals through ingestion, inhalation, or skin contact, resulting in various health issues.

Blue-green algae is a type of bacteria

Blue-green algae, also known as cyanobacteria, are a type of bacteria. They are microscopic organisms that are naturally present in lakes and streams. They are often referred to as algae due to their similarities with eukaryotic algae, including morphological characteristics and ecological niches. However, they are classified as bacteria because they lack a membrane-bound nucleus, mitochondria, Golgi apparatus, chloroplasts, and endoplasmic reticulum.

Cyanobacteria are capable of performing photosynthesis, like algae, and they can be found in fresh, salt, or brackish waters. They thrive in warm, calm, sunny weather and water temperatures above 75°F. Under favourable conditions, cyanobacteria can reproduce rapidly, forming dense concentrations called blooms. These blooms can discolour the water and produce floating mats or scums on the surface. They can also cause unpleasant odours and affect the taste of the water.

While not all blue-green algae or algal blooms are toxic, certain varieties can produce toxins that are harmful to humans, animals, and the environment. These toxins can accumulate in the entrails (guts) of fish and, occasionally, in the muscle (fillet). Exposure to these toxins can cause various symptoms in humans, including vomiting, diarrhoea, rash, eye irritation, cough, sore throat, and headache. In the long term, consumption of untreated water containing high levels of blue-green algal toxins may be associated with an increased risk of liver cancer.

To minimise the potential risks associated with blue-green algae, it is recommended to avoid swimming, water skiing, or boating in areas where algae are visible, the water is discoloured, or unpleasant odours are present. It is also important to avoid drinking untreated water, as boiling or simple treatment options may not effectively remove the toxins. Public water suppliers are responsible for treating, disinfecting, and monitoring drinking water to address possible contaminants, including blue-green algae and their associated toxins.

Pollution increases algae growth

Blue-green algae, or cyanobacteria, are microscopic organisms that are naturally present in lakes and streams. They are not algae but types of bacteria that perform photosynthesis. While blue-green algae are typically not harmful to humans, certain varieties can produce toxins that are linked to illness in humans and animals. These toxins can accumulate in the guts of fish and, occasionally, in the muscle (fillet).

Once in the water, nitrogen and phosphorus act as fertilizers, causing an explosion of algae growth. This overgrowth of algae consumes oxygen and blocks sunlight from reaching underwater plants, leading to the formation of "dead zones" where aquatic life cannot survive due to a lack of oxygen. The frequency and duration of these dead zones have increased since they were first noticed in the 1970s, with over 166 dead zones documented nationwide in the US.

The climate crisis is exacerbating the conditions that favor algal blooms. Curbing climate change and adopting regulations to reduce nutrient pollution are crucial steps in mitigating the negative impacts of algal blooms on human health, ecosystems, and local economies.

Algae blooms can be toxic

Algal blooms, or the overgrowth of microscopic algae or algae-like bacteria, can be toxic. This toxicity is referred to as a harmful algal bloom (HAB). HABs produce toxins that are dangerous to humans and potentially other organisms. Any type of algae can proliferate into a HAB under the right conditions. Toxin production can be stimulated by environmental factors such as light, temperature, salinity, pH, and nutrient levels.

HABs can occur in fresh, salt, or brackish waters and are most commonly found in lakes, ponds, and other freshwater systems. They can also be found in brackish and saltwater environments. HABs are typically identified by discoloured water or surface scums, which can be shades of green, blue-green, yellow, brown, purple, white, or red. The water may also have a paint-like appearance or a swamp-like odour.

HABs can have detrimental effects on human health, with symptoms including vomiting, diarrhoea, rashes, eye irritation, cough, sore throat, and headaches. In extreme cases, HABs can even be fatal. Exposure to HAB toxins can occur through swallowing or swimming in affected waters, eating poisoned fish or shellfish, or inhaling airborne droplets of affected water.

In addition to impacting human health, HABs can also harm aquatic ecosystems and local economies. For example, the overgrowth of algae can deplete oxygen levels in the water, clog the gills of fish and invertebrates, and smother corals and submerged aquatic vegetation. HABs have been linked to the decimation of blue crab populations in the Chesapeake Bay area.

To mitigate the risks associated with HABs, it is recommended to avoid swimming or recreating in waters with visible algal blooms and to rinse with fresh water if exposed. It is also crucial to avoid using untreated water for drinking, cooking, or brushing teeth, as boiling or simple treatment options may not effectively remove algae toxins.

Blue-green algae affects human health

Blue-green algae, also known as cyanobacteria, are a type of bacteria that are naturally present in lakes and streams. They are often found in warm, shallow, and undisturbed nutrient-rich waters that receive a lot of sunlight. Under favourable conditions, blue-green algae can proliferate, forming blooms that discolour the water and produce floating scums. These blooms can be harmful to human health in several ways.

Firstly, blue-green algae blooms can produce toxins called cyanotoxins, which can accumulate in the guts and, to a lesser extent, the muscle tissue (fillets) of fish. Consuming fish caught in areas with high levels of blue-green algae blooms may therefore pose a risk to human health. While recent studies suggest that cyanotoxins do not accumulate at significant levels in fish fillets, it is recommended to avoid eating fish organs, as higher levels of cyanotoxins have been found in the livers of fish from waterbodies that regularly experience blooms.

Secondly, direct exposure to blue-green algae blooms can also cause health issues in humans. If water containing blooms is swallowed, or if airborne droplets are inhaled, a range of symptoms may occur, including vomiting, diarrhoea, rash, eye irritation, cough, sore throat, and headache. These symptoms typically appear within hours to two days of exposure. It is important to note that boiling or treating the water with chlorine or other disinfectants does not remove the toxins, and may even increase toxin levels.

In addition, there is limited evidence from human studies suggesting a possible link between long-term consumption of untreated water with high levels of blue-green algal toxins and an increased risk of liver cancer. However, the participants in these studies were also exposed to other factors associated with liver cancer, so the contribution of algal toxins to this risk remains uncertain. Nonetheless, it is recommended to avoid drinking untreated surface water to minimise the risk of exposure to blue-green algae and their associated toxins.

Furthermore, blue-green algae blooms can have indirect effects on human health by impacting aquatic ecosystems. For example, blooms can kill underwater plants, disrupting food webs and contributing to the decline of certain species, such as the blue crab in the Chesapeake Bay area. Such ecological disruptions can have cascading effects on human communities that depend on these natural resources for their livelihoods and well-being.

Overall, while not all blue-green algae produce toxins, it is important to take precautions to minimise exposure to blue-green algae blooms and to seek medical advice if any symptoms occur after potential exposure.

Blue-green algae impacts aquatic ecosystems

Blue-green algae, also known as cyanobacteria, are photosynthetic bacteria that are usually present in lakes, streams, and other bodies of water. While not all blue-green algae are harmful, certain conditions can cause them to form blooms that have detrimental effects on aquatic ecosystems and human health.

Blue-green algae thrive in warm, calm, sunny weather and water temperatures above 75°F. When the weather conditions are favourable and there is an abundance of nutrients like nitrogen and phosphorus, rapid algae growth can occur, leading to the formation of blooms. These blooms can produce toxins that are harmful to humans, livestock, pets, and aquatic life.

The toxins released by blue-green algae blooms can accumulate in the guts and, occasionally, the muscle tissue of fish. While consuming fish caught in areas with minor blooms may be safe if the guts are discarded, it is recommended to wait a week or two after the bloom subsides to ensure toxin-free fillets. Anglers should also be cautious of eating fish from waters where blooms are a frequent occurrence, as the potential accumulation of toxins in the fillets is uncertain.

In addition to impacting fish, blue-green algae blooms can also harm other aquatic organisms. The blooms consume oxygen and block sunlight from reaching underwater plants, leading to the creation of "dead zones" where aquatic life cannot survive due to a lack of oxygen. This disruption in the ecosystem can have cascading effects, such as the decimation of blue crab populations in the Chesapeake Bay area due to the loss of their critical habitat.

Furthermore, blue-green algae blooms can have direct impacts on human health. People who come into contact with contaminated water through activities like swimming, boating, or drinking untreated water can experience various symptoms, including vomiting, diarrhoea, rashes, eye irritation, cough, sore throat, and headaches. While boiling or treating water at home may not effectively remove the toxins, public water suppliers are equipped to address these contaminants through treatment, disinfection, and monitoring processes.

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