California Sea Grant College Program

Diatoms are single-celled, microscopic algae with intricately built, often beautiful, silicon shells. As the sea’s primary producers, they provide food directly or indirectly for nearly all the sea’s fishes and marine mammals. They are the base of the marine food chain, and as such their abundance is a good indicator of the ocean’s productivity—the more diatoms, the greater the ocean’s productivity. Ocean productivity has profound implications for marine biodiversity and for commercial fisheries, particularly the wet fish fishery in California: squid, anchovy and sardine.