The peculiar moss ball

An algae, a pet, a home decoration, a companion in the fish tank – the moss ball (Aegagropila linnaei) may be described in many different ways. And it can be found right here in the northern Bothnian Bay.

Aegagropila linnaei has grown into a ball, picture taken in dry land.
Moss ball (Aegagropila linnaei) (Photo by Linnea Bergdahl, County Administrative Board of Norrbotten)

This peculiar looking algae may also be called marimo, which is a japanese word that literally translates to “ball seaweed”. The moss balls are no alien eggs but rather a specie of filamentous green algae (Cladophora) that grows into the shape of round balls. They may be found in lakes in for example Iceland, Scotland and Japan. Today they have become popular in fish tanks and you can order your very own moss ball online if you’d like to have one at home.

A moss ball on a hand, size of it is about 4 cm.
The thin filamentous threads of the algae are shaped into a solid ball. The ones found in the northern Bothnian Bay usually range in the size from a pea to a golfball (Photo by Manuel Deinhardt, Metsähallitus)

During inventories within the SEAmBOTH project area, divers have found the moss balls at deeper bottoms consisting of hard surfaces such as rocks and stones. It is difficult for other plants to grow in the deeper, darker waters on hard surfaces where they have difficulties attaching themselves to the bottom. The moss ball on the other hand favors these conditions and is often the dominating specie in these areas.

Sea bottom covered with moss balls, some sand showing in between them.
The moss balls attached to the bottom (Photo by Jon Ögård, Metsähallitus)
A moss ball freely in the water, a diver poking on it.
The moss balls may sometimes be living free floating, and can then be found drifting around in the water column. (Photo by Lari Järvinen, Metsähallitus)

If you want to know more about the species of the SEAmBOTH area, see species guides on the Results page!

Written by Linnea Bergdahl, County Administrative Board of Norrbotten

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