Sand dollars are flat, disk-shaped marine animals, a type of echinoderm related to sea urchins and starfish. Their appeal as beach finds comes from their unique, star-like pattern and smooth, bleached white appearance once they are no longer alive. When alive, they possess a velvety texture due to tiny spines covering their bodies, typically gray, brown, or purplish. The familiar white disks found on shores are their skeletons, known as tests, cleaned and whitened by the sun and ocean.
Understanding Sand Dollar Habitats
Sand dollars primarily inhabit sandy or muddy ocean floors in shallow coastal waters. They prefer environments free from heavy vegetation like seagrass, as this can impede their movement and burrowing. Most reside in subtidal zones, just below the low tide line, where they access food and shelter.
Sand dollars are adapted for a life spent on or just beneath the surface of the sediment. They use specialized spines and cilia to burrow into the sand, which helps them hide from predators and strong currents. This burrowing behavior also allows them to filter tiny food particles from the water or sand. Sand dollars often gather in large groups on the seafloor.
Prime Locations and Conditions for Discovery
The best opportunities to find sand dollars arise during low tide, particularly spring tides, which expose more of the sandy seafloor. Early mornings are often ideal, as calmer conditions and lower sunlight glare improve visibility.
Storm activity can increase the chances of finding sand dollars washed ashore. Powerful waves and currents during or after a storm can dislodge them from their sandy beds and carry them closer to the shoreline. While this can be a productive time for beachcombing, caution is advised due to potentially rough ocean conditions.
Look for them along the high-tide line or in ripple lines in the sand where they might be partially exposed. Coastal areas with gentle currents or near piers are known for more frequent sand dollar finds.
Ethical Collection and Preservation
When collecting sand dollars, it is important to distinguish between live and dead specimens for ethical beachcombing. A live sand dollar is typically darker (gray, brown, or purplish) and covered in tiny, velvety spines that may show slight movement. They might also leave a harmless yellowish stain. If you encounter a live sand dollar, gently return it to the water.
Dead sand dollars are typically bleached white or pale beige, lack velvety spines, and feel smooth and rigid. These are suitable for collection. Rinse them thoroughly with fresh water to remove sand or debris.
For further cleaning and to achieve the classic white appearance, a diluted bleach solution (1 part bleach to 4 parts water) can be used for a short soak (15-30 minutes), followed by a thorough rinse. A gentler solution of white vinegar and water can also be used.
After cleaning, allow the sand dollar to dry completely, preferably in sunlight, to whiten and harden it. To make them more durable, a thin coat of a 1:1 mixture of white school glue and water can be applied. Always follow local regulations regarding shell collection.