Life Interstitial

What does it take to live between the grains of sand?

Published April 28, 2017

This article is the third in a multi-part exploration of meiofauna. The first is “The Micro Monsters Beneath Your Beach Blanket” and the second is “Here Be Tiny Dragons (and Other Micro Beasts).”

The beach is constantly on the move. As tides, winds, and currents move water across the beach surface, sand grains shift. On calm days, the movement is subtle, but during storms, the sediments churn in nature’s rock tumbler. An ever-shifting substrate means that no algae or animals can live on the beach surface. Animals such as snails, clams, and worms burrow down, but the real action is between the grains of sand, in the interstices, where a booming metropolis of microscopic organisms slither and crawl in the film of water.

This interstitial community, called meiofauna, is rich and diverse, and includes individuals from most animal phyla. And although they’re small, these animals are as complex in their physiology as those millions of times their size, from worms to wombats.

To survive in a sandy mobile home, which alternates between a marine environment when the tide is in and a terrestrial one when it’s out, meiofauna have a variety of adaptations. 

Note: we have taken a few liberties for visual clarity. In reality, most meiofauna lack pigmentation and are transparent. As well, the organisms and the sand grains are not to scale. Consider that in just one millimeter, there could be about 22 of the smallest meiofauna laid end to end. When you’re that tiny, even a sand grain is a mighty hill to climb.

Click on the creatures in this interactive image to see what it takes to live in the sand.