Phycology, also known as algology, is the scientific study of algae, a diverse and essential group of photosynthetic organisms found in aquatic environments. Algae range from microscopic single-celled phytoplankton to large, multicellular seaweeds like kelp. These organisms play a critical role in global ecosystems, serving as primary producers in both freshwater and marine habitats. They contribute significantly to oxygen production and are a fundamental part of the food web, supporting a vast array of aquatic life.

The study of algae is crucial due to their ecological, economic, and environmental importance. Algae are responsible for nearly half of the world's oxygen production through photosynthesis, making them vital to maintaining atmospheric balance. Additionally, they act as a key food source for marine organisms, from zooplankton to large fish and mammals. Their ability to rapidly absorb carbon dioxide makes them important players in global carbon cycling, influencing climate regulation.