What lives in the Swash Zone?
Next time you go for a nature walk, stop walking, look around you and learn everything you can about that one single spot.
So much of nature escapes our attention unless we look closely, sit on the ground, observe for a period of time, get dirty. Choose a spot and discover the details and hidden treasures (and nightmares) of that single place, that small ecosystem.
For example beach walks are full of discovery - we see beautiful shells, creatures washed ashore by the surf, birds foraging. But lets just stop in one spot, in the swash zone (the part of the beach where the waves wash in and out) of a South Carolina Beach and look more closely at what lives there.
The picture at the top of this page is only a portion of the whole. Below is the rest of the picture. Doesn't look like there is much going on here.
But look closer.... There are holes in the sand. And some of the holes look different than other holes. And some have "stuff" around the opening. .... Huh! Look at that! There were a bunch of shells there a minute ago and they just disappeared! .... I wonder what all those birds are feeding on. Look there! Water coming out of that hole.
There is more going on here than first meets the eye.
Lets start with those disappearing shells, as they are one of my favorite creatures. Here are links to a couple of videos that show this disappearing act.
The coquinas are very small, very beautiful clams that live in the shallow surf zone and the swash zone. They lay on the surface of the sand in bunches feeding on phyto and zooplankton and other small organisms, until a wave comes along. Then they quickly put their foot in the sand and hold on. They bury themselves so they won't get washed away or eaten by some fish. I have only seen this live once. It is mesmerizing. They disappear, reappear, disappear, reappear.... Here is another video. So cool.
Moving on to those holes in the sand.
Many creatures including worms, crabs and ghost shrimp live in the sand of the swash zone.
The ghost shrimp is a wimpy looking, pale, shrimp-like animals that burrows in the swash zone. Despite its looks, it is vital to maintaining a healthy ecosystem. When ghost shrimp are absent from a swash zone, few other creatures can live there. The ghost shrimp dig and build extensive burrows in the sand and 'process' organic material (those little sprinkles in one of the pictures above). This is bioturbation (smile - new word - see the box below).
In another of the holes is the villain of this ecosystem, the clamworm.
Bioturbation (click to follow the link to wikipedia) is critical to maintain a healthy intertidal ecosystem. It drives biodiversity by providing habitat, oxygenating, mixing the sediment. This happens through burrowing and the ingestion and defecation of sand grains.
There are various types of bioturbation. I find it funny (and amazing) that there are upward conveyors (ghost shrimp - move sediment from down to above) and downward conveyors (some worms) which move the sediment from surface to below. All are needed.
Nature is amazing.
These worms are aggressive predators with an impressive set of tools and weapons. They are quite mobile (well, for a worm) have smany sensors, four eyes and huge pincers. Watch the picture below of the cute cuddly worm face turn into a monster .
Clamworms will eat just about anything they come across that they can grab with those pincers. One nature book describes this - "The prey is grasped with the "jaws" projecting from the clamworm's muscular pharynx, which is everted and distended for the attack. It is then withdrawn into the digestive cavity by inverting the pharynx." Shiver.
Other holes are home to worms and crabs such as lugworms and mole crabs and among the sand grains smaller organisms such as plankton, sand fleas, algae and diatoms live.
All these creatures, hiding under our feet, are important in the food cycle and diversity of a healthy swash zone ecosystem.
And that ecosystem is vital to many of the shorebirds we observe, to their ability to migrate through or raise their young on our coast.
This picture is by Kelly Luikey, one of my favorite nature photographers.
On your next beach walk, stop, sit, observe, dig, see what you find. Sometimes we see more by focusing on less.