What are blue-green algae?

Blue algae are cyanobacteria and live on light, carbon dioxide and nutrients dissolved in the water. Blue algae were the first organisms on earth and they produce oxygen. Many nutrients in the water can cause blue-green algae blooms.

The video and photo are showing these organisms present in a sample of water from a port in the southern Netherlands. The sample was taken shortly after exceptionally hot days with an outside air temperature of 40 degrees Celsius. With a blue-green algae bloom, the many blue-green algae on the water surface can come together and form a floating layer. Many types of blue-green algae make poisons. Contact with or swallowing blue-green algae can cause health problems.

Cyanobacteria are among the oldest forms of life that we know. Some researchers believe that they can be traced back to cyanobacteria 3.5 billion years ago, while others question this. In any case, fossil and chemical evidence shows with great certainty that cyanobacteria were already around 2.7 billion years ago. Thanks to their photosynthetic activity, these cyanobacteria caused one of the biggest environmental changes in the history of the earth. The atmosphere changed around 2.2 billion years ago from an almost oxygen-less to an oxygen-rich one. This made life as we know it now possible.

Note:
In 1674 Antoni van Leeuwenhoek saw “groene ranckjens” (green strings) through his microscope in the water of Lake Berkel in the Netherlands. It was long thought that these were thread algae. After a thorough inspection of Van Leeuwenhoek's descriptions, it was discovered that this must have been cyanobacteria, better known as blue-green algae. Bacteria now appear to have been discovered two years earlier than previously thought.