AMAZONAS
While A. linnaei does not seem to be directly harmed by elevated nutrient levels—the
success of Marimo Balls in hobby aquariums bears testimony to this—in a wild aquatic
ecosystem this condition triggers freshwater algae blooms that block light penetration
through the water column or smother the Marimo Balls and A. linnaei attached form
with algal mats. Increased siltation, a consequence of deforestation and other land use
changes, and dredging smother Marimo Balls under sediment or permanently erase their
sandy lake bottom habitats.
A study in the Netherlands (Boedecker & Immers 2009) used historical records and
diligent snorkeling, SCUBA, canoe, and wading surveys in lakes to assess changes in
the distribution of A. linnaei and the Marimo Ball over time. Herbarium specimens and
published accounts spanning from 1906 to 1967 indicated Marimo Ball occurrence for
at least eight different sites in the Netherlands. But rigorous field verifications found
just one small surviving patch of A. linnaei mat attached to a mussel shell in Bovenwi-
dje, a small, heavily impacted lake close to the shore of the North Sea in the province of
Overijssel.
Another recent, more geographically extensive census (Boedeker, Eggert, Immers,
& Smetts 2010) used literature citations and more than 1,200 preserved specimens
examined at 28 herbarium collections to document historical records of A. linnaei oc-
currence and changes over time. Herbarium specimen records documented A. linnaei
(both attached and lake ball forms) at 32 different sites (the long Baltic Sea shoreline
counted as a single site) during the 1800s and early decades of the 1900s, but just seven
during the period 1975–2007.
Corroborating this evidence and showing a comparable trend, reviews of published
literature and direct inquiries with public universities and water resources management
authorities expanded the number of known historical locations to 235, with a decline
leading up to the recent 30-year period to 101 locations. The lake ball form of A. linnaei
has been impacted more heavily by environmental changes than the attached form.
Maps and tables in this paper show historical and recent records concentrated in
Northern Europe, Japan, and Iceland, with a single recent record in North America.
The authors also cited collection from wild populations as a potential threat. Many of
the Marimo Balls in the aquarium hobby trade apparently originate from the Shatsk
lakes in Ukraine, although some of this material might be used for aquaculture propa-
gation and production of many more Marimo Balls.Marimo Balls in the planted aquarium
The oldest kind of aquarium ecosystem, the simple planted vase, is enjoying renewed
popularity. Illuminated with shafts of natural sunlight or the bright directional beamBlue Tiger Shrimp, Caridina
cantonensis, on a Marimo,
whose genus name comes from
the Greek for “goat hair.”LEFT: FOAP AB / SHUTTERSTOCK; TOP: HANS-GEORG EVERS