AMAZONAS
faces required for establishment of the mat form, so in
this way A. linnaei expands its suitable habitat. By rolling
about with the waves, Marimo Balls clear their filament
mats of light-blocking sediments and can also disperse
to new or more favorable micro-sites. The Marimo Ball
form even helps the alga to make use of the water habit
in three-dimensional space. Under the right conditions,
vigorous photosynthesis entrains oxygen bubbles within
larger, hollow Marimo Balls. With this buoyancy advan-
tage, the Marimos slowly ascend in the water column,
like magic, to reach brighter sunlight near the surface.
The Marimo Ball form also allows the alga to substantial-
ly increase biomass over a given area of its rare habitat. A
study in Japan (Togashi, Sasaki & Yoshimura 2014) used
a geometric model and field observations to demonstrate,
not surprisingly, that when the diameter of Marimo Balls
in tightly spaced situations surpassed the small size of
1.6 inches (4.13 cm), their biomass was
substantially more than that of mat colo-
nies covering the same area: these are never
able to surpass 5 cm^3 /cm^2. This effect is
accentuated even more in places where the
Marimo Balls are stacked up several deep,
like oranges in a crate. The spherical shape
creates gaps through which shafts of light
can reach balls buried under their neigh-
bors, while wave action also reshuffles them
so that previously shaded Marimo Balls can
find their way closer to the top.
The ocean environment is generally
much more stable over the course of a
single year or longer period of time than
bodies of fresh water, and it is probably for
this reason that most saltwater algae have
not developed desiccation-resistant disper-
sal propagules like the ones most freshwater
algae groups use. Instead, marine algae rely
on wave action to carry their zoospores,
gametes, or other water-borne dispersal
forms to new places. Freshwater algae can
disperse hundreds of miles or more as
wind-borne spores, and most occur over
broad geographic areas, but A. linnaei, like
its closest relatives in the ocean, can only
disperse through water or on short trips
through the air in the plumage of birds.
Sexual reproduction has apparently been
observed only a few times in A. linnaei, and
it is likely that it almost always multiplies
vegetatively via small fragments. This limi-
tation, in combination with slow growth
and special habitat requirements, prob-
ably explains the rarity of A. linnaei and its
restriction to a small number of lakes.
The most famous Marimo Ball loca-
tion is Lake Akan in Hokkaido, Japan. Thisarea of northern Japan still has some relatively pristine
landscapes and waters, and Marimo Balls grow in several
other Hokkaido lakes. Every year in early October, local
people host a three-day festival at Lake Akan honoring
the Marimo Ball. The Japanese cherish the Marimo Ball
as a national treasure, a “Special Natural Monument,”
and it is unlawful to collect any from the wild, although
the free-floating filaments are gathered from a few
sites to be aquacultured as Marimo Balls for sale in the
aquarium plant trade.Missing Marimo Balls
Like so many aquatic ecosystems and organisms, wild
populations of A. linnaei and their habitats have been
heavily impacted by human activities. The most significant
changes driving Marimo Ball local extinctions are prob-
ably eutrophication and alteration of natural hydrology.A Marimo in a micro-
biotope enclosed in a
lightbulb jar.