Actually, The answer is tiny organisms known as cyanobacteria, or blue-green algae. These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and, yes, oxygen. "What it looks like is that oxygen was first produced somewhere around 2.7 billion to 2.8 billon years ago. Harmful cyanobacteria blooms may affect people, animals, or the environment by: y blocking the sunlight that other organisms need to live. Cyanobacteria blooms can steal the oxygen and nutrients other organisms need to live. y making toxins, called cyanotoxins.
