Cultural Snapshots

Marimo: Great Balls of Green Algae Are a Natural Wonder

Environment

Balls of velvety green algae called marimo are particularly associated with Lake Akan in Hokkaidō, where they can grow to up to 30 centimeters in diameter.
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A Fragile Existence

Marimo is a kind of velvety green algae known for forming naturally underwater into balls. Lake Akan in Hokkaidō is famous as the home of the world’s largest marimo balls, which can grow to around 30 centimeters in diameter and have been designated as a national special natural monument. Visitors can observe them by taking a sightseeing cruise that includes entry to the Marimo Exhibition and Observation Center on the lake’s Chūrui Island.

According to researchers, climate change is now altering the conditions in the lakes that are the habitats for marimo, posing a threat to these fragile growths.

The Marimo Festival was established in 1950 to raise awareness about protecting these unique algae. It is held on October 8–10 each year with the participation of local Ainu people, and includes a ceremony and traditional performances.

(Originally written in English. Banner photo © Pixta.)

Hokkaidō nature