Algae are essential components of aquatic ecosystems. They perform photosynthesis, which means they use sunlight to convert carbon dioxide and water into glucose and oxygen. This process not only provides energy for the algae themselves but also produces oxygen that is vital for the survival of many aquatic organisms. Algae can vary greatly in size and complexity, from tiny phytoplankton to large seaweeds like kelp. Their ability to thrive in diverse environments makes them a key player in food webs and nutrient cycling in aquatic habitats.