Phytoplankton are plantlike microorganisms that live on the water's surface in aquatic biomes. As photosynthesis organisms, phytoplanton produce much of Earth's oxygen as a byproduct. Explain the ecological impact of a decline in phytoplankton by providing examples from the organism through the ecosystem levels of organism.

Phytoplankton serves as food for virtually all the organisms living in an aquatic environment. It is a primary food producer and serves as the foundation of aquatic food web. If there is a decline in the amount of phytoplankton, the organisms which feed directly on the plant may reduce significantly as a result of dire competition for food, this in turn will affect the organisms which feed on the dying out organisms and the trend will move in a similar way until it affect all the organisms living in that particular aquatic habitat.