sea snow

Throughout the world's oceans, tiny particles swirl, drift, and fall like snowflakes from the ocean's upper levels. Appropriately named "sea snow," these particles are made of debris, or dead parts of plants and animals, along with other organic stuff such as sand and poop! Sea snow provides food for many marine animals. It also acts as a transport system, carrying matter from the sunlit surface to the deep seafloor.

Also known as: marine snow
Description: tiny, nonliving particles that sink in the ocean
Size: particles at least 0.5 millimeters in diameter
Found; in every ocean of the world
First person to study sea snow: marine biologist Mary Silver from the University of California, Santa Cruz

Image credits: main image, courtesy of REVEL Project, University of Washington.