What is the role of harmful algae in water pollution?

Harmful algae play a major role in water pollution when they reproduce excessively, a phenomenon known as "Harmful Algal Blooms" (HABs). These algae, which occur naturally in bodies of water, can produce toxins that harm humans, animals, fish, and the entire ecosystem. This excessive growth depletes oxygen in the water and blocks sunlight from other organisms, threatening aquatic life and affecting drinking water quality and recreational activities [1].

How do harmful algal blooms form?

Harmful algal blooms (HABs) form when toxin-producing algae grow excessively in a body of water. These blooms can become visible to the naked eye, appearing in various colors such as green, blue-green, red, or brown, depending on the type of algae. The presence of a harmful bloom cannot always be determined by sight alone, as some may grow near the bottom of water bodies [1].

Several factors contribute to these blooms, including rising water temperatures, especially in summer, and the presence of excess nutrients such as fertilizers or sewage entering water bodies through runoff. These environmental conditions stimulate algae growth and reproduction, leading to the formation of harmful blooms [1].

Effects of harmful algae on human health

Humans can be exposed to harmful algal toxins in several ways, including eating contaminated fish, swimming in or drinking contaminated water, and inhaling toxin-laden air. It is important to know that cooking contaminated seafood or boiling contaminated water does not eliminate these toxins [1].

Health effects vary depending on the type of algae and the toxins they produce. For example, consuming seafood contaminated with Alexandrium algal toxins can lead to paralytic shellfish poisoning, which may cause paralysis and even death. Pseudo-nitzschia algae also produce domoic acid, which can cause vomiting, diarrhea, confusion, seizures, permanent short-term memory loss, or death when consumed in large quantities [1].

In freshwater, blue-green Microcystis bacteria dominate, producing hepatotoxins that can cause gastrointestinal diseases and liver damage. Children and the elderly may be more sensitive to harmful algal toxins, and populations that rely heavily on seafood may be susceptible to long-term health effects due to repeated exposure to low levels of these toxins [1].

Environmental and economic impacts

In addition to health risks, harmful algal blooms cause significant environmental damage. They deplete oxygen in the water, leading to the death of fish and other aquatic organisms. Blooms that form near the water's surface also block sunlight from reaching organisms in the depths [1].

These blooms also impact the economy, especially in the fishing and recreational sectors. Businesses lose significant revenue if they are forced to close or reduce operations due to harmful algal blooms [1].

Prevention and what to do if you suspect a bloom

To prevent diseases related to harmful algal blooms, local health guidelines regarding the safety of caught seafood and drinking water sources must be followed [1]. If you suspect a harmful algal bloom in a body of water, avoid touching or drinking the water, and avoid fishing or eating seafood from that area. Any suspected blooms should be reported to local authorities for necessary action. For more information on environmental health, you can visit Environmental Health Challenges in Jordan (Arabic) [2].

Medical references

• Algal Blooms
• Environmental Health