How did marimo end up on a beach in Schull?

Last week, a reader wrote, “Sir, I live in West Cork since four months. I come from Brittany.

West Cork is a marvellous place! Yesterday, I made a little walk on the strand in Schull. I found many “green moss” bowls on the sand. Could you help me to resolve the mystery of the Green Moss Bowls of Schull?” A photo of a handful of spherical green balls of moss followed.

I will be frank; I had never seen these ‘things’ in Ireland. But the photo jogged a memory; I had seen something similar in a Tokyo fish market when I lived in Japan in the mid-1970s. I wondered what they were at the time, but thought them to be man-made, or man-woven, another example of Japanese minaturism, art and ingenuity.

I assumed they had been created as suitable ‘window dressing’ for the fish — fish and seaweed, green balls and silver fish. The freshness of the multi-coloured fruits of the sea, glittering on their marble slabs, was reinforced by these wet, dark green balls around them.

Now, harvested on a beach in Schull, I realised that they were not spun by clever oriental fingers, but by nature itself. Nature, however, makes so many wonderful things that we would be more impressed were they man-made. We are enthralled by the silkworm spinning its cocoon, but even more so when we see it unspun and transformed into garments shimmering in the light.

As I researched, I found that memory had served me well. Marimo balls, if not indigenous to Japan, are most common there; “marimo” is Japanese for “ball seaweed”. Composed of filaments of an algae, Aegagropila linnaei, they grow into spherical shapes with a velvety appearance, and form colonies. They occur only in northern hemisphere lakes in Iceland, Estonia, Scotland and, primarily, in Lake Akan in Japan’s northern island of Hokkaido, where the native Ainu people traditionally consider them to be divine manifestations.

So, how did a small crop of marimo end up on a beach in Schull? They can, apparently live, and even thrive, in saline water, but I could find no mention of their occurrence in Ireland. However, I came upon a paper published by the National University of Ireland, Galway (Guiry, M.D. & Guiry, G.M. 2015), which told me that Cladophora balls, or marimo, were declared a Japanese Natural Treasure in 1921 and in 1952 elevated to Special Natural Treasure status.

The paper mentions that they have existed in the United Kingdom — other studies mention Scotland, and a map of sites I found includes Ireland. However, I can find no details.

In their natural environment of shallow, sandy-floored lakes, the gentle action of waves rolls the clump of filaments around causing them to form near-perfect spheres where all sides receive light for photosynthesis. This produces oxygen, giving the balls the happy knack of rising to the surface. When the oxygen escapes they again sink to the bottom.

As the Guiry study notes, “Another benefit of being spherical is that when silt and other fine debris collects on the uppermost surface [ ], gravity causes it to naturally rotate with the weight and the debris will fall off.”

Seen rolling lazily around the lake floor, and rising and falling on columns of warmer water, the balls seem to be the nearest things to fish. Not surprisingly, some people keep them as aquarium ‘pets’. They are traded on eBay.

Cladophora algae balls were first discovered in Lake Zeller, Austria, in 1824 and then in the UK, Russia, Iceland, Sweden and Estonia . Today, they are still be found in Lake Myvatn in northern Iceland and in Lake Akan in Japan.

Lake Akan has been made a National Park and Japanese biologists, including Emperor Hirohito, have made a study of the plants. They are depicted on two Japanese (and one Icelandic) postage stamps.

Once sold as keepsakes in Japan, it was believed that a healthy, well looked-after marimo would make its owner’s wishes come true. However, human collecting and pollution eventually made them so endangered that in the early 1950s, a conservation campaign asked Japanese citizens to return their beloved marimo to the lakes whence they came. Significantly, people did so in large numbers.

Marimo have since become an environmental icon in Japan. However, here in Ireland, since shipwrecked marimo cannot be returned to source, should I find one I will certainly nurture it in a glass bowl of water, and enjoy it for the beautiful plant it is.