Microalgae

Microalgae are tiny, plant-like organisms (usually single-celled) that live mostly in water and make their own food using sunlight.

• How they survive: Like plants, they do photosynthesis—they take in carbon dioxide and water, use sunlight, and make food, releasing oxygen as a by-product.
• Why they matter so much: Even though they are microscopic, huge numbers of microalgae live in oceans and lakes, so together they produce a very large share of the oxygen in Earth’s air.
• They are the “first food” in water: Many aquatic food chains begin with microalgae. Tiny animals (like zooplankton) eat them, and then fish and bigger animals depend on those.
• Not all “algae” are big and leafy: Seaweeds you can see are macroalgae. Microalgae are so small that you usually need a microscope to see them clearly.
• Useful to humans: Some microalgae can be grown in tanks and used as nutrient-rich supplements, help in water cleaning, and can even be used to make biofuel.
• A simple way to picture them: Think of microalgae as tiny floating “green factories”—making food and oxygen while also feeding many living things in water.