Algal blooms
Harmful algal blooms (HABs) are caused by the rapid growth of certain types of algae, which can release toxins that can harm aquatic life, wildlife and human health.
Blue-green algae, also known as cyanobacteria (covered in our previous post), can bloom under certain conditions, such as warm water temperatures, high levels of sunlight, and an excess of nutrients, such as phosphorous and nitrogen, in the water. However, not all blooms are blue-green algae and not all blooms of blue-green algae are harmful. The reason for this is that not all species of cyanobacteria produce toxins and some blooms can be beneficial for the ecosystem.
Sometimes harmful
Some species of cyanobacteria can produce toxins, such, that can harm aquatic life, wildlife, and human health. The presence of these toxins can depend on the species of cyanobacteria present and the environmental conditions in which they are growing. Some of the most common toxins and affects produced by HABs include:
- Microcystins: These are a type of cyanotoxin produced by certain species of cyanobacteria, also known as blue-green algae. Microcystins can cause liver damage, skin irritation, and even death in severe cases.
- Saxitoxins: These are a type of neurotoxin produced by certain species of dinoflagellates. Saxitoxins can cause paralysis and death in aquatic life, and can also cause shellfish poisoning in humans.
- Domoic acid: This is a type of neurotoxin produced by certain species of diatoms. Domoic acid can cause memory loss, seizures, and even death in severe cases.
- Brevetoxins: These are a type of neurotoxin produced by certain species of dinoflagellates. Brevetoxins can cause respiratory distress and neurotoxic shellfish poisoning in humans.
- Lipopolysaccharides (LPS): These are a type of endotoxin produced by certain species of bacteria. LPS can cause inflammation and septic shock in humans and animals.
- Amnesic shellfish poisoning (ASP): This is caused by domoic acid, a neurotoxin produced by certain species of diatoms. It can cause memory loss, seizures and death in severe cases.
These toxins can have severe impacts on aquatic life, wildlife and human health, by affecting the nervous system, causing gastrointestinal symptoms, skin irritation, and even death in highly severe cases. Additionally, some of these toxins can accumulate in seafood and shellfish, creating a danger for human consumption.
Non-harmful species
Other species of cyanobacteria do not produce toxins and can be beneficial for the ecosystem by providing food for aquatic animals and helping to purify the water. These blooms can occur under similar conditions as the toxic blooms, but without the harmful effects.
The timing and location of the bloom, as well as the specific species of cyanobacteria present, can also play a role in determining whether a bloom is harmful or not. For example, certain species of cyanobacteria may produce toxins under certain conditions, such as high water temperatures, while other species may not. Additionally, a bloom that occurs in a remote area may not have the same impact on human health and the environment as a bloom that occurs in a heavily populated area.
Triggers
Typically a sudden influx of nutrients rich in phosphorous and nitrogen couples with the correct weather conditions to enable a HAB. Sources can include untreated sewage, fertilizer run off, industrial discharge, or sudden erosion events as these make the nutrients required for a bloom available.
Our best method to mitigate against these blooms is to ensure that extreme weather events or poor planning do not enable system and infrastructure failures that allow nutrients to enter water courses in the first place.
Summary
Blue-green algae, also known as cyanobacteria, can bloom under certain conditions, such as warm water temperatures, high levels of sunlight, and an excess of nutrients, such as phosphates and nitrates, in the water. However, not all blooms of blue-green algae are harmful. Some species of cyanobacteria can produce toxins, such as microcystins, that can harm aquatic life, wildlife, and human health, while others can be beneficial for the ecosystem by providing food for aquatic animals and helping to purify the water. The timing, location and specific species of cyanobacteria present can play a role in determining whether a bloom is harmful or not
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