We have dollars lying around Kingston!

As part of Stillwaters monitoring in the Carpenter Creek and Appletree Cove estuary, we have been making observations of what is living in the slough area (also called by some the estuary) before and after the new bridge installation.  As some of you may know, there is a sand dollar colony on the slough side of the bridge. You should go take a look!

Sand dollars — Dendraster excentricus — are small disc-shaped marine animals in a family of sea creatures called echinoderms and are closely related to sea stars, sea urchins and sea cucumbers. When alive, these animals look purplish-black and are often partially buried in the sand. After they die their skeleton, or test — a hard calcareous body — turns white from sun bleaching. Those white flat tests, with what looks like a five-petaled flower etched into the surface, are what you most commonly find on the shore.

Sand dollars typically live beyond mean low water or in pools of water on top of or just beneath the surface of sandy or muddy areas.  Some of you may have seen them on the Hansville shoreline.

They have many “tube feet” (like starfish) with tiny hairs called cilia. These tube feet look almost like a purple velvet coat. They use their tube feet for burrowing into the sand and for getting oxygen. They also use their tube feet, along with the cilia, to catch food. They move their cilia, assisted by a mucous coating, to transport the food they capture to their mouth opening in the center of star-shaped grooves on their underside.

The mouth has a five-toothed structure called Aristotle’s lantern for chomping food. The Aristotle’s lantern is what rattles when you shake a dead sand dollar. They eat plankton, plants, and animals and organic particles that they glean from the water or sandy bottom. Sometimes a sand dollar “chews” its food for 15 minutes before swallowing. It can take two days for the food to digest. Kind of a fun mental picture to have as you drive over the bridge — all that chewing going on!

The common name for these creatures is sand dollar, but other names are sand cake and cake urchin. Relatives in more tropical waters are called sea biscuits because they are more puffed up, like a biscuit. They reproduce by sending sperm and eggs into the water, so living in close colonies aids their successful reproduction.

They have a life cycle that includes several phases. After fertilization, they become floating plankton before they start forming their calcareous test and settle down to become a benthic (bottom dwelling) creature. After they mature, they have few predators. Some scientists believe these animals live from six to 10 years.

The sand dollar bed in our slough is in the area of the newly formed pool that is just to the east of the old scour hole. It is easily accessible at low tide by walking under the bridge. It is likely that there was a colony there for some time before the bridge project, since there are adult animals they’re now in a dense cluster.

The bed is an irregular shape of approximately 13 feet by 20 feet. When you walk around it you first notice the dead, white tests.  Then, as your start seeing your first purplish disk, you begin to see more and more! It is fascinating to see them lying flat and fully exposed or partially buried with just an edge sticking out of the mud.

Take the opportunity to walk over and see what is living in this glorious natural system remaking itself before our eyes!

— Contact Betsy Cooper at betsycooper1@gmail.com.