What Causes the Glowing Waves on Cape Cod Beaches?

The ethereal blue-green glow seen on Cape Cod beaches at night is caused by dinoflagellates—microscopic, single-celled algae.

These planktonic organisms produce light through bioluminescence. When waves agitate the water, the mechanical stress triggers a chemical reaction in the dinoflagellates, emitting a flash of light. Massive blooms create spectacular glowing surf, especially in late summer and fall.

While beautiful, some dinoflagellate species can produce toxins; local advisories should be heeded during intense blooms.