What is the primary role of phytoplankton in marine ecosystems?

Phytoplankton play an essential role in marine ecosystems as they form the base of the marine food web. As primary producers, they use photosynthesis to convert sunlight into energy, creating organic matter from carbon dioxide and nutrients in the water. This process not only supports their own growth but also provides a crucial food source for a wide range of marine organisms, from tiny zooplankton to larger fish and marine mammals.

Without phytoplankton, the entire marine food web would be severely affected since many species depend on them for nourishment. Thus, their role as primary producers is fundamental to supporting aquatic life and maintaining ecosystem health.

While decomposing organic matter is important for nutrient recycling, regulating ocean temperature relates more to physical processes rather than a specific organism’s role, and providing habitat for marine animals is typically the responsibility of larger organisms such as coral reefs and seagrass rather than phytoplankton.