What Are Marimo Moss Balls?

Have you ever been to a lake on a warm summer day? Maybe you went fishing in Crater Lake or Lake Baikal. You might have explored the many islands of the Great Lakes. Or perhaps you just relaxed on a shore, observing the calm surface of a lake and wondering what might be beneath.

Truly, the lakes of our world provide wonderful habitats. Each one could contain various plants and animals. Some are teeming with life, while others are devoid of it. Today’s Wonder of the Day is about a living organism that exists in only a few lakes around the world. What are we referring to? Marimo moss balls!

That name is somewhat misleading. Marimo moss balls are not actually moss, but rather algae. The algae grow long filamentous strands, which become entangled as they roll along the bottoms of freshwater lakes. This is how they form a sphere that resembles moss. The largest ones can be more than a foot in diameter!

Have you ever seen marimo moss balls in person? If so, you may know that they tend to float during the day and sink at night. Experts believe they do this for two reasons. The first is related to photosynthesis—they float to the surface during the day to absorb sunlight. The second reason is their circadian rhythms. The organisms rise and sink according to their own internal clock.

Marimo moss balls are also known as lake balls. They were once found in many locations across the world. They have been observed in Iceland, Siberia, Australia, Ukraine, Ireland, and Japan, just to name a few. However, experts have noticed a peculiar trend in the past few decades. The lake balls have started to disappear.

In the last 30 years, marimo moss balls have only been sighted in about 50 percent of their known habitats. Today, they are only abundant in two places—Lake Mývatn in Iceland and Lake Akan in Japan. Why the significant decline? Experts attribute it to pollution, pesticides, and climate change, which have placed the lake balls on the endangered species list.

The lake balls have also been impacted by tourism and the aquarium trade. Many people like to keep marimo moss balls as pets, prompting companies to harvest them from freshwater lakes. Additionally, tourists have been known to take the lake balls as souvenirs. This issue has become so widespread that it caught the attention of the Japanese government. In 1977, the government requested that anyone who had taken a lake ball from Lake Akan return it. This was just one effort to save the marimo population.

In Japan, the indigenous Ainu people have their own way of helping the marimo. They hold a festival each year at Lake Akan called Marimo Matsuri. The festival aims to appreciate Mother Nature and protect the marimo moss balls. At the festival, people can learn about the lake balls and witness special rituals that honor them. They also get to learn about Ainu culture through folk songs and dance performances.

Would you like to see the marimo moss balls at Lake Akan? Would you like to learn more about the Ainu people? Perhaps one day you can attend Marimo Matsuri yourself! It’s a fantastic opportunity to gain more knowledge and celebrate nature.

Give it a Try

Are you ready to continue learning? Seek assistance from an adult to try the following activities!

• Expand your knowledge about the Ainu people. How long have they resided in Japan? What is their culture like? Did you discover any other interesting facts? Summarize what you have read for a friend or a family member.
• Were you aware that Japan’s Lake Akan is part of a national park? Learn more about the park from here. Now, envision planning a trip to visit the park. What are you most looking forward to seeing? Explain the reasons behind your excitement. Create your own Wonder Blog on Wix and compose a post about which part of Akan-Mashu National Park you would like to explore.
• Freshwater lakes, rivers, and ponds serve as incredibly diverse habitats. Request an adult family member to take you on a field trip to a nearby freshwater location. What kinds of plant and animal life can you find there? Keep a record of the organisms you encounter. You can even attempt to sketch a few of them! When you return home, select one organism to delve deeper into and ask your family member to assist you in conducting further research online.

Sources of Wonder

• https://ohmatsuri.com/en/articles/hokkaido-marimo-matsuri (accessed 18 Aug. 2020)
• https://www.forbes.com/sites/grrlscientist/2018/08/29/why-do-japanese-moss-balls-float-by-day-and-sink-by-night/#509d351b4886 (accessed 18 Aug. 2020)
• https://www.nationalgeographic.com/news/2016/09/lake-balls/ (accessed 18 Aug. 2020)
• https://academic.oup.com/bioscience/article/60/3/187/256937 (accessed 18 Aug. 2020)

FAQ

1. What are Marimo moss balls?

Marimo moss balls are a type of aquatic plant that are native to lakes in Japan, Estonia, and Iceland. They are often referred to as “living moss balls” due to their unique appearance and ability to grow. Marimo moss balls are actually a type of algae, known scientifically as Aegagropila linnaei. They have a round shape and a velvety texture, resembling a fluffy green ball. These plants are popular in the aquarium hobby and are often kept as pets. Marimo moss balls require low to medium light and thrive in cool water temperatures.

2. How do Marimo moss balls grow?

Marimo moss balls grow by absorbing nutrients from the water around them. They have a slow growth rate, typically adding only a few millimeters in diameter each year. As they grow, they develop a dense outer layer while maintaining a soft and spongy interior. Marimo moss balls reproduce by dividing themselves into smaller fragments, which then grow into separate balls. This process can take several years. With proper care and maintenance, Marimo moss balls can live for many decades.

3. What are the benefits of having Marimo moss balls in an aquarium?

Having Marimo moss balls in an aquarium offers several benefits. Firstly, they help to improve water quality by absorbing nitrates and other pollutants. This can help to create a healthier and more balanced environment for fish and other aquatic animals. Marimo moss balls also provide natural filtration by trapping debris and excess nutrients in their dense growth. Additionally, their unique appearance adds visual interest to an aquarium, creating a natural and serene atmosphere.

4. How do I care for Marimo moss balls?

Caring for Marimo moss balls is relatively easy. They require low to medium light, so placing them near a window or using artificial aquarium lights is sufficient. It is important to keep the water temperature cool, ideally between 68-78°F (20-25°C). Regular water changes should be done to maintain water quality. Marimo moss balls can be gently squeezed to remove any trapped debris or excess air. If they become discolored or brown, they may need more light or a water change. Overall, Marimo moss balls are low-maintenance plants that can thrive in various aquatic environments.

5. Can Marimo moss balls live outside of water?

No, Marimo moss balls cannot live outside of water. They are aquatic plants that require a constant water source to survive. If removed from water for an extended period of time, they will eventually dry out and die. It is important to ensure that the water they are kept in is clean and free from any harmful chemicals or pollutants. While they can tolerate a wide range of water conditions, maintaining a suitable environment is crucial for their health and longevity.