Another Potential Climate Victim: Cute Fluffy Algae Balls

As well as being a popular part of Lake Akan, marimo algae balls are also popular with aquarists.

photo by Depositphotos

During the winter months, at the bottom of Lake Akan in Hokkaido, Japan, harmless underwater algae that can grow larger than basketballs are protected from death by a layer of ice on the surface of the ocean. water. According to researchers from the University of Tokyo, this shield is expected to thin due to global warming, bringing the orbs to the list of species threatened by climate change.

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Known as marimo seaweed balls, the lifeform is somewhat of a hero in Japan, where it is commonly (incorrectly) known as marimo moss balls. Soft, light green balls have their own mascot (slightly different in color), they are often kept as a kind of pet in aquariums and have their own festival. There is even an observation center in the middle of Lake Akan in Hokkaido, which attracts over half a million visitors every year.

Scientifically known as Aegagropila linnaei, the balls are formed by rolling in the lake. They start as small as a pea, grow about five millimeters a year, reach a foot wide, and can live for centuries. Like trees, they develop growth rings with age. The number of marimo balls living in lakes around the world is rapidly declining, with pollution and human intervention being cited as the main causes of their extinction. Now the largest marimo balls remain in Lake Akan itself.

Due to the global extinction of the species and a desire to preserve the remaining specimens in Lake Akan, a team of scientists from the University of Tokyo undertook a study to see how access to sunlight during the winter months could affect these organisms.

We know that marimo can survive sunlight in warm summer waters, but the photosynthetic properties of marimo in cold winter temperatures have not been studied, so we were fascinated by this point. We wanted to know if Marimo tolerate this and how they react to low temperature and high light environment.

says Project Assist. Teacher. Masaru Kono of the University of Tokyo Graduate School of Science

So the team went to Lake Akan and measured the intensity of sunlight underwater, both when the lake was ice-free and when it was covered in ice. They then collected several small balls of marimo about 10–15 cm (3.9–5.9 in) in diameter and brought them back to the lab. There, they exposed strands of algae from the balls to ice and artificial light, which recreated the conditions seen in the lake.

In cold water A. linnaei it goes into hibernation, with only a thin layer of algae fibers on its surface, which is very different from the more durable and hairy “summer coat”. Therefore, in winter, it is not able to withstand as much sun as in summer. In fact, the researchers found that the balls could only withstand up to six hours of sunlight a day in cold water before the cells involved in photosynthesis died, leading to the death of the entire organism. They also found that although the beads degraded after four hours of exposure to strong light, 30 minutes of moderate light helped them recover. Interestingly, moderate light was needed to help them recover; darkness did not have the same effect.

Marimo balls in the aquarium (Aegagropila linnaei)
Marimo balls in the aquarium (Aegagropila linnaei) | photo by Depositphotos

Since Lake Akan receives over 10 hours of sunshine a day during the winter months, the ice and snow that completely covers the lake prevents the marimo balls from being hit by too many rays. This coating typically reaches a thickness of about 20 inches (508 mm). However, as the ice thins due to warming and more sunlight enters the winter water, scientists fear the orbs are at higher risk of extinction.

To investigate this further, researchers will study the effect of excess light on the entire marimo beads, not just the strands, to see if the organism’s circular structure can provide it with additional protection against harmful radiation.

In this study, we used dissected filamentous cells, so we did not consider the effect of marimo’s spherical structure and how it might protect against exposure to bright light. However, if surface cell damage is exacerbated by prolonged exposure to direct sunlight, this can, in the extreme case, affect the behavior of their round bodies and lead to the demise of the giant marimo. So you should constantly monitor the conditions of Lake Akan in the future.

Kono said

The research results have been published in International Journal of Molecular Sciences.

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Source: University of Tokyo Images used in the entry Depositphotos

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