Phytoplankton are microscopic water based organisms. Most are single-celled plants. One tiny phytoplankton is invisible to the eye, but filling the oceans in trillions they are key to the Earth’s health. They sit at the foundation of the ocean-based food web. Through photosynthesis, phytoplankton produce half of the air we breath. Phytoplankton are also the ocean’s biggest consumers of carbon dioxide, at a scale equivalent to forests and other land plants. Irreplaceable. As our oceans are threatened by climate change, phytoplankton are in unprecedented distress. Some species are dying out, some are migrating to new waters — disrupting food chains on a global scale.