Brown Grass Shrimp

It lives on things that are going somewhere.

Mats of torn seaweed and floating seagrass drift across open water for weeks, and they carry a full community with them: shrimp, crabs, small fish, juvenile turtles, snails and the animals that eat all of those. It is one of the few genuinely mobile habitats in the sea, and for the animals living on it the surrounding open ocean is a desert with a raft moving through it.

This shrimp is one of the residents, colored to match brown weed, slender and clinging. Where the raft goes, it goes, and mats crossing between coasts carry populations of shrimp and crabs to places their own swimming could never take them. That is how many coastal invertebrates got where they are.

It is also why the same species turns up in the top few meters and at seventy: the animal is not choosing a depth, it is choosing a piece of drifting weed, and the weed goes where the water takes it.