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Bay Nature magazineJuly-September 2011

Hidden Life in the Sand

by on July 01, 2011

Creative Commons photo by Bruce Washburn, flickr.com/btwashburn.
Creative Commons photo by Bruce Washburn, flickr.com/btwashburn.

To see a World in a Grain of Sand
And a Heaven in a Wild Flower,
Hold Infinity in the palm of your hand,
And Eternity in an hour.

In these famous lines from a poem he wrote more than 200 years ago, William Blake reminds us of the importance of small things, especially in nature. But he probably didn’t know there really is a world between the grains of sand along the ocean shore. Did you know there may be thousands of tiny animals in that handful of damp sand you picked up by the water?

Though it’s fun for us to play where the waves wash onto shore, it’s pretty hard for animals to live there: There’s no stable ground, and large areas flood or dry out as the tide changes. But, in fact, tiny animals are able to make their homes in the moist spaces between grains of sand at the water’s edge.

These creatures are called meiofauna (pronounced MY-oh-FAWN-uh), a word that refers to their small size. The largest meiofauna are smaller than the period at the end of this sentence–too small to see with our naked eyes. Under a microscope, some look like bristly worms or shrimp, and one looks enough like a pudgy hairless bear that it’s called a water bear.

Even though they’re tiny, meiofauna are important members of the beach environment. They help keep beaches clean by eating bits of even tinier dead organisms, and they in turn are food for other animals.

Since meiofauna are hard to see without a microscope, you might want to look for slightly larger sand animals. But even those can be a challenge to find.

For example, you won’t find beach hoppers if you look during the day. That’s when they stay moist and cool by burrowing into the sand in the “splash zone” above the high tide line. But with a flashlight at night, you may see thousands of them hopping about and eating beach wrack (piles of washed-up kelp and other ocean debris).

Beach hoppers resemble inch-long grayish-white shrimp with long red-orange antennae. They’re tasty morsels for many larger animals, especially birds–another good reason for them to stay buried during the day. If they’re disturbed, they dig rapidly into the sand head first.

Another beach animal that burrows rapidly is the sand (or mole) crab. But it burrows backwards. In fact, sand crabs can only move backwards, whether they’re digging, crawling, or swimming. Their burrows are in the “swash zone,” where the waves wash up and back on the beach. Because the tide is always changing, the crabs must move and rebury themselves often to stay in that zone.

In their burrows, they stand on end with only their long-stalked eyes and feathery antennae above the surface. As the water from a wave recedes, they extend their antennae and filter out tiny plankton to eat. It’s rare to see live sand crabs outside their burrows, but people who dig fast know they’re egg-shaped, grayish, and up to an inch and a half long. The bigger ones are the females, who carry thousands of orange eggs attached to their abdomens in the summer.

Sand crabs have good years and bad years. Some years millions of them pack together on a beach, and some years there are only a few. But even in the worst years, the sand is still full of life: There are whole worlds in there!

Get Out!

Small sand-dwelling animals are not easy to find. But you can check out tiny bay shore animals under the microscope in the Crab Cove Visitor Center at Alameda’s Crown Beach.

At an ocean beach, you might discover sand crabs or even beach hoppers. To find sand crabs, dig a small hole at the water’s edge, and swirl the water that fills the hole. Look for sand crabs swimming (backwards!) in the hole before they quickly bury themselves. Collections of small V-shaped marks or bubbles in the sand where the water has just receded are likely signs of sand crabs underneath. To see beach hoppers, use a flashlight to look at piles of washed-up kelp away from the water’s edge after dark. While you’re at it, look for the skeletal remains of sand crabs in those piles. Because there are waves and tides at night just like during the day, be sure to check tide tables before you go, and always keep your attention on the ocean.

Most recent in Habitats: Freshwater, Bay, Marine

See all stories in Habitats: Freshwater, Bay, Marine


RAFAEL SANCHEZ on June 2nd, 2013 at 9:11 pm


Dan Rademacher on June 2nd, 2013 at 9:32 pm

Rafael, can you give us more to go on here? Where were you? And what do you mean “pocked”? Hit?

Marissa C on March 17th, 2014 at 7:56 am

I live in Naples, Florida. Two days ago I was standing with my feet in the sand about to play a game of volley ball at the Naples Pier, when something bit my toe. I didn’t think anything of it until this morning when it was painful for me to walk, and my toe is completely swollen. My second toe on my right foot. There’s only one “bite” mark, and no puss or discoloration. Any ides on what it could be from? Thanks!

Melody on March 21st, 2014 at 3:18 pm

I was not bit but I was standing in the “swash zone” and when the wave washed over my feet, hundreds of tiny black worms shot out of the ground all around me at the same time! They disappeared back in to the sand just as quick. I got out of the water and watched and they would shot back out about every 5th wave. What are they??

Sue Rosenthal on March 25th, 2014 at 11:41 pm

Where did you see the tiny black worms, Melody? (What state? What beach?) Did this happen recently?

Melody on April 2nd, 2014 at 12:12 pm

Sue, I was at Fort De Soto Beach in Pinellas County Florida. It was this year (2014) in March.

June m. on July 19th, 2014 at 5:25 pm

I have been trying to find out what those little worm like creature who live in the splash zone and come up through the wet sand to feed. If you happen to be standing there they come up between your toes and tickle you. They do not bite. They make their home in Massachusetts, on Sagamore beach. Just on the edge of the Cape Cod Canal.
I am sure they must be other places, however, this is the only place I have ever seen them. They are grayish about 3 in. Long and look a little like a long thin fish, about the size of a sardine or anchovies.

if someone can solve this mystery, I would be gratefull. this has bugged me for 40 years me folol

Daughter of Jesus on March 6th, 2015 at 6:28 pm

Me and my friends were digging in the sand. When white things were moving in my sand castle I caught some and they were about 1cenameter white with grey 6-8 legs. If someone knows what this is tell me pls

Lola on June 7th, 2015 at 3:37 pm

I recently went to mexico ( i got every year) and i always notice these small green and black worms in the sand like on the tide and there is hundreds of them I’m always afriad to step in one because I don’t know what would happen but they’re really skinny and long and very slimy they go underneath the sand sometimes and then come back up but they’re only where water is Never in a dry area but the weird thing is they’re only there in the morning and they’re gone around 4 in the afternoon does anybody have any idea what they could be?

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