Sand dollars are unique marine invertebrates found on sandy ocean floors globally. These flat, disk-shaped creatures are echinoderms, making them relatives of sea urchins and starfish. When alive, they are often covered in tiny, velvety spines that give them a brown, gray, or purplish hue. Sand dollars inhabit shallow coastal waters, filter feeding on microscopic algae and organic particles from sediment. Their feeding and burrowing activities help clean the water and aerate the sandy seabed, contributing to the overall health of marine ecosystems.
Natural Causes of Death
Sand dollars face various natural threats throughout their lives, contributing to their mortality. Predators like sea stars can prey on sand dollars by enveloping or crushing their delicate tests. Crabs also pose a threat, using their strong claws to break open sand dollars. Certain fish species and seabirds like gulls also consume sand dollars, especially those exposed near the shoreline. Their slow movement and limited defense mechanisms make them vulnerable to these predators.
Natural environmental shifts also contribute to sand dollar deaths. Strong storms and currents can dislodge sand dollars from their sandy habitats, burying them or washing them ashore where they cannot survive. Extreme fluctuations in water temperature or salinity also negatively affect sand dollar populations. Like all living organisms, sand dollars have a natural lifespan, typically ranging from 6 to 10 years in the wild. As they age, they can become more susceptible to diseases, which can weaken them and lead to their demise.
Human-Related Causes of Death
Human activities significantly impact sand dollar populations, leading to their decline. Over-collection by beachgoers is a notable threat, particularly in popular tourist areas. Removing live specimens from their habitat depletes populations and disrupts the natural ecosystem.
Habitat destruction and disturbance also pose a considerable risk to sand dollars. Activities like dredging, coastal development, and boat anchoring can physically damage their sandy habitats. This destruction makes areas uninhabitable, buries sand dollars, or removes the sediment they rely on for survival and reproduction. Destructive fishing practices, like bottom trawling, further devastate the seafloor where sand dollars reside.
Marine pollution represents another serious human-related cause of sand dollar mortality. Oil spills, chemical runoff from agriculture and industry, and microplastics contaminate their environment. These pollutants can directly harm sand dollars through ingestion or absorption, impairing their reproduction, growth, and immune functions. Microplastics can be ingested, potentially delaying development, causing reproductive issues, and weakening their ability to fight off disease.
How to Help Sand Dollars Survive
Individuals can contribute to sand dollar conservation by adopting responsible practices when interacting with marine environments. When collecting sand dollars, it is important to only take empty, white “skeletons” or tests that have washed ashore. Live sand dollars, identifiable by their dark color and moving spines, should always be left undisturbed in their natural habitat. If a live sand dollar is found stranded, gently returning it to the water can help ensure its survival.
Respecting marine environments more broadly also supports sand dollar populations. This includes refraining from littering on beaches and reducing overall plastic use to minimize pollution. Supporting clean ocean initiatives and participating in beach cleanups can also positively impact their habitats. Avoiding disturbance of sand dollar beds, especially during low tide, helps protect these delicate creatures from being crushed or damaged. Reporting unusual marine life strandings or significant pollution incidents to local authorities or conservation groups can also aid in their protection.