Phytoplankton blooms are rapid increases in the population of microscopic plants in oceans and freshwater bodies. These tiny organisms, which are crucial for the aquatic food web, thrive in nutrient-rich waters, often triggered by factors like sunlight and temperature. When conditions are right, phytoplankton can multiply quickly, leading to visible green or blue-green patches on the water's surface. While these blooms can support marine life, excessive growth can deplete oxygen levels and produce toxins, resulting in harmful effects on fish and other aquatic organisms.