Introduction to Foraminifera: The Ocean's Tiny Historians

Published: 2026-01-15

Foraminifera are single-celled protists that construct shells, or tests, from calcium carbonate or agglutinated sediment grains. With over 10,000 living species and more than 40,000 known fossil species, they are among the most diverse and abundant groups of marine organisms.

Their tests accumulate on the seafloor in staggering quantities — foraminiferal ooze covers approximately 30% of the ocean floor. Because different species thrive under specific environmental conditions, their distribution in sediment cores provides a detailed record of past ocean temperatures, productivity, and circulation.

Modern micropaleontologists combine traditional taxonomy with geochemical analysis of individual shells. The oxygen isotope ratio of foraminiferal calcite reflects the temperature and ice volume at the time of shell formation, making these tiny organisms one of our most powerful tools for reconstructing Earth's climate history.