Phytoplankton & CO2
One group of creatures produces 70% of the earth's oxygen and also consumes carbon dioxide at an amazing rate. They are phytoplankton, and most are tiny single-celled organisms.
Phytoplankton come in many shapes and forms. The majority are single-celled plants, but some are bacteria and others are protists. Common types of phytoplankton are cyanobacteria, green algae, diatoms, dinoflagellates, and coccolithophores.
Phytoplankton plays an important role in human life in that they produce 70% of the oxygen we breathe. A much greater amount than terrestrial plants.
They are part of the carbon cycle, as they consume atmospheric carbon dioxide (CO2). CO2 resides naturally in the atmosphere, but human beings, mostly through the burning of fossil fuels, have released ever greater amounts into the atmosphere.
Along with CO2, phytoplankton need sunlight and other nutrients to survive.
At certain times, phytoplankton grow at an explosive rate over the course of days or weeks, creating what is called a "bloom." These blooms may last several weeks, even though an individual phytoplankton lives only for a few days. Despite being of a microscopic size, Phytoplankton blooms are so large they are clearly seen and photographed from satellites.
Aside from providing oxygen, phytoplankton are a major part of the food chain which includes everything from tiny zooplankton to shrimp, jellyfish, fish and whales.
Sometimes, phytoplankton can produce biotoxins, killing marine life and people who eat this marine life. "Red tides" are a type of toxic algal bloom. Once the bloom is over, the bacteria feeding on the dead phytoplankton deplete the oxygen in the water, thereby suffocating other animals.
These tiny creatures are truly a fascinating link in the chain of life.