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© 2004 Smithsonian Institution

Macroscopic algae (Ventricaria ventricosa), also known as "bubble algae" or "sea pearl," is widespread algal species that can withstand low light. Each of the bubbles is a single cell, making it one of the largest single-celled organisms known, reaching up to 5 centimeters in diameter. They are often found in mangrove forests, growing on the mangrove roots, and some people consider it a pest.