Plankton decline refers to the significant reduction in the populations of microscopic organisms, including phytoplankton and zooplankton, that float in oceans and freshwater bodies. These tiny creatures are crucial for the aquatic food web, serving as the primary food source for many marine animals, including fish and whales. Factors contributing to their decline include climate change, pollution, and overfishing, which disrupt their habitats and reproductive cycles. The decrease in plankton populations can have serious consequences for marine ecosystems and global climate. Phytoplankton play a vital role in producing oxygen and absorbing carbon dioxide, thus influencing the Earth's climate. A decline in these organisms can lead to reduced oxygen levels in water and affect the overall health of marine life, ultimately impacting human food sources and economies reliant on fishing.