Britannica Sources used in this answer

Why are plankton important to marine food chains?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram showing ocean zonation by depth and region, with labeled layers: littoral, sublittoral, bathyal, abyssal, and hadal along the seafloor, and epipelagic, mesopelagic, bathypelagic, and abyssalpelagic in open water. The littoral zone is at the high-tide mark. Vertical scale marks photic and aphotic zones from surface to 10,000 meters. — Marine ecosystem Zonation of the ocean. Note that in the littoral zone the water is at the high-tide mark.

Plankton are essential to marine food chains because they form the foundational base of the trophic pyramid in oceanic ecosystems. Their importance is primarily categorized by their roles as producers and consumers:1

Primary Producers: Phytoplankton are photosynthetic organisms that convert solar energy into organic substances. They are the primary producers of the marine community, providing the essential energy that supports nearly all other oceanic life.2341
Primary Consumers: Zooplankton act as heterotrophic consumers that feed on phytoplankton. By bridging the gap between primary producers and higher trophic levels, they serve as a critical food source for a vast array of marine animals, including fish, crustaceans, and marine mammals.241

Beyond their direct role in nutrition, the photosynthetic activity of plankton significantly influences the Earth's biosphere by regulating atmospheric composition. Furthermore, through the creation of marine snow, plankton transport organic material from the upper ocean layers to the seafloor, providing vital sustenance for benthos and other deep-sea organisms.2