Harmful algal blooms occur when algae, which live in both sea and fresh water, grow uncontrollably and produce harmful effects on people, fish, mollusks, marine mammals, and birds. In addition, although the diseases caused by harmful algae are rare, they can cause death in extreme cases.
How are they formed?
Algae are simple plants that form the basis of food webs. However, under the right conditions, algae can grow out of control, producing toxins that kill marine animals and even cause human disease. Other algae are not toxic, but they consume all the oxygen in the water as they decompose and clog the gills of the fish. Others discolor the water, form huge pools on beaches, or contaminate drinking water. Ultimately, this event is known as harmful algae bloom or HAB.
Algal blooms occur naturally in the seas. However, human activities that damage ecosystems have increased in intensity and frequency. Pollution, climate change or invasive species are some of the factors that influence the increase in harmful algae.
Algae are sometimes linked to overfeeding. When nutrients (mainly phosphorus and nitrogen) from sources such as agriculture flow into bays, rivers and seas, they accumulate at a rate that supercharges the algae found in the environment. In other cases, algae grow due to the increase in the temperature of the seas or due to climatic phenomena such as hurricanes, floods or droughts.
Can you predict an algae outbreak?
Currently, scientists forecast a harmful algal bloom in the same way that they forecast a hurricane or tropical storm. This forecast provides an early warning, so food banks (fish and shellfish) that could be contaminated by algae toxins are checked.
In addition, notices are also posted in coastal areas where there is a direct risk to people’s health.
