The Largest Migration on Earth

The largest migration on Earth does not happen on land but in the oceans. Every night at sundown, a great mass of mostly small transparent sea creatures, some no larger than a pea, rises from from a depth of a few hundred meters to the topmost layers of the planet’s oceans to feed on carbon-rich phytoplankton. They then return to the deep, where they deposit that organic, carbon-rich material as waste. As a result of this vertical migration – the largest on Earth – these little-known creatures are helping to keep the planet’s atmospheric carbon dioxide in the deep sea, thereby regulating the Earth’s surface temperature.

Creatures of the Vertical Migration

Sea butterflies are mollusks that live their whole life in the upper layers of the ocean. This adult specimen photographed in Florida is approximately the size of a quarter or a little bigger. The glowing bulb at the center of its body is its stomach. Credit: Susan Mears.
Box jelly off the coast of Florida at a depth of about 30 to 40 feet. This larva is between about two and two and a half inches. Unlike some other varieties found around the world, most box jellies in this region sting but are not fatal. Credit: Susan Mears
Mantis shrimp larva off the coast of the island of Lembeh in Indonesia, about an inch long. When fully grown, these carnivorous creatures use their forelimbs to prey on hard-shelled mollusks and fish. Credit Susan Mears.
Larval tube anemone. Credit: Susan Mears
The extremely rare gargoyle cusk eel, usually found in deep water. Credit: Susan Mears
Sharpear enope squid. Adults of this species live in deep water and are rarely seen. This larva is about fingernail-size. Credit: Linda Ianniello
Larval thimble jellyfish. Credit: Linda Ianniello
Eel larva. This specimen is about three to four inches long. These larvae are transparent, fast-moving and hard to photograph. Credit: Linda Ianniello
Adult tube anemone, measuring three to three and a half inches. Tube anemones can spread out and shrink their larger tentacles around the smaller feeding tentacles at the top of their body. Credit: Susan Mears.
Alciopidae: A pelagic worm with eyes capable of forming an image. Credit: Jim Mears.
Two views of a paralarval wunderpus octopus taken in Anilao, the Philippines. The body is about the size of a thumbnail. The spots are developing chromatophores that help the octopus blend into its environment. Credit: Linda Ianniello


The text for this post is adapted from the “Science in Images” series published online by Scientific American. All photos are from that series in an article titled, “See the Mysterious Sea Creatures That Only Come Up at Night” by Andrea Gawrylewski. All but two photos were taken off the coast of Florida.

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