Their Natural Habitat
Sand dollars, flattened sea urchins, inhabit sandy or muddy ocean bottoms. They prefer shallow coastal waters, from the intertidal zone down to subtidal depths of about 30 to 50 feet. These marine invertebrates burrow just beneath the surface of the sand, creating a protective layer.
Their preferred environment is calm, protected areas like bays and lagoons. Sand dollars are filter feeders, using specialized cilia and mucous to capture microscopic food particles, such as plankton and detritus, from the water column or the sand. They move slowly across the seabed, ingesting organic material present in the sediment.
Optimal Conditions for Discovery
Finding sand dollars on a beach depends on specific environmental conditions. Low tide is a favorable time, as more of the beach and intertidal zone become exposed. Searching during the lowest tides of the month, often associated with full or new moons, can be particularly productive.
Significant weather events, such as storms or strong currents, can dislodge sand dollars from the seafloor and transport them closer to shore. Following such events, especially within a day or two, beaches may yield more specimens. Sheltered coves and wide, gently sloping sandy flats are the most productive locations, as these areas allow sand dollars to accumulate without being immediately swept back out to sea or broken apart by strong waves. Early morning is another optimal time, as fewer beachcombers will have already searched the area.
Techniques for Locating Them
When searching for sand dollars, focusing attention along the wrack line can be effective. This line, marking the highest reach of the tide, accumulates marine debris, including empty sand dollar tests. Sifting through loose sand or examining the shallow water at the edge of the receding tide can also reveal hidden specimens.
Observing areas where the sand appears slightly disturbed or where small depressions are visible might indicate a buried sand dollar. A small scoop or sifter can help uncover buried specimens without damaging them. Patience and a keen eye are beneficial, as sand dollars can blend seamlessly with their sandy surroundings.
Distinguishing Live from Dead Specimens
When encountering a sand dollar, it is important to determine if it is alive before collecting it. Live sand dollars have a darker coloration, ranging from purplish-brown to reddish-brown, and are covered in short, velvety spines that give them a slightly fuzzy appearance. These spines are used for locomotion and feeding, and a live sand dollar may exhibit subtle movements.
In contrast, a dead sand dollar, often referred to as a “test” or “shell,” is white, off-white, or grayish in color, completely smooth, and lacks any spines. These empty tests are lightweight and brittle, as all organic material has decayed and washed away. Collecting only these smooth, spine-free, white specimens ensures ethical beachcombing and helps preserve the living marine ecosystem.