Microscopic Illustrations

Prickly halimeda (Halimeda opuntia), a calcified alga, rises in the lower foreground of this Smithsonian watercolor by Gina, 2026. Its jointed flat green segments rest on a blue-green reef floor, with tall finger-like growths behind, a spotted yellow-green coral at right and rounded boulders at left. The dead segments add to reef sand.