SHALLOW LAKES
Cyanobacteria blooms cannot be controlled by Effective
Microorganisms (EM
) from mud- or Bokashi-balls
Miquel Lurling • Yora Tolman •
Frank van Oosterhout
Published online: 7 March 2010

The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract In controlled experiments, the ability of
‘‘Effective Microorganisms (EM, in the form of
mudballs or Bokashi-balls)’’ was tested for clearing
waters from cyanobacteria. We found suspensions of
EM-mudballs up to 1 g l-1 to be ineffective in
reducing cyanobacterial growth. In all controls and
EM-mudball treatments up to 1 g l-1 the cyanobac-
terial chlorophyll-a (Chl-a) concentrations increased
within 4 weeks from &120 to 325–435 lg l-1. When
pieces of EM-mudballs (42.5 g) were added to 25-l
lake water with cyanobacteria, no decrease of
cyanobacteria as compared to untreated controls
was observed. In contrast, after 4 weeks cyanobacte-
rial Chl-a concentrations were significantly higher in
EM-mudball treatments (52 lg l-1) than in controls
(20 lg l-1). Only when suspensions with extremely
high EM-mudball concentrations were applied (i.e., 5
and 10 g l-1), exceeding the recommended concen-
trations by orders of magnitude, cyanobacterial
growth was inhibited and a bloom forming concen-
tration was reduced strongly. In these high dosing
treatments, the oxygen concentration dropped ini-
tially to very low levels of 1.8 g l-1. This was most
probably through forcing strong light limitation on
the cyanobacteria caused by the high amount of clay
and subsequent high turbidity of the water. Hence,
this study yields no support for the hypothesis that
EM is effective in preventing cyanobacterial prolif-
eration or in terminating blooms. We consider EM
products to be ineffective because they neither
permanently bind nor remove phosphorus from
eutroficated systems, they have no inhibiting effect
on cyanobacteria, and they could even be an extra
source of nutrients.
Keywords Biological control
Eutrophication

Lake restoration
Microcystis aeruginosa
Introduction
Anthropogenic nutrient over-enrichment of surface
waters is the primary cause of cyanobacterial blooms
and nuisance scum’s (Fogg, 1969; Reynolds &
Walsby, 1975; Reynolds, 1987; Paerl, 1988, 2008).
The massive blooms are a serious environmental
problem and pose a risk to human health, as blooms
Guest editors: M. Meerhoff, M. Beklioglu, R. Burks, F. Garcı´a-
Rodrı´guez, N. Mazzeo & B. Moss / Structure and Function of
World Shallow Lakes: Proceedings from the 6th Shallow Lakes
Congress, held in Punta del Este, Uruguay, 23–28 November,
2008
M. Lurling (&)
Y. Tolman
F. van Oosterhout
Aquatic Ecology & Water Quality Management Group,
Department of Environmental Sciences,
Wageningen University, P.O. Box 47, 6700 AA
Wageningen, The Netherlands
e-mail: miquel.lurling@wur.nl
Y. Tolman
Waterboard Delfland, P.O. Box 3061, 2061 DB Delft,
The Netherlands
123
Hydrobiologia (2010) 646:133–143
DOI 10.1007/s10750-010-0173-3

may contain a variety of very potent toxins, and may
produce stomach-turning odors and may cause high
turbidity, anoxia, fish kills, and food web alterations
(Codd et al., 2005; Dittmann & Wiegand, 2006;
Paerl, 2008; Paerl & Huisman, 2008, 2009). Climate
change is expected to aggravate hazardous blooms
favoring cyanobacterial dominance in a wide range of
aquatic ecosystems (Paerl & Huisman, 2008, 2009).
This expectation is underpinned by the coincidence
of the two hottest summers in Europe, 2003 and 2006,
since recording started (Luterbacher et al., 2004;
Rebetez et al., 2009), with major cyanobacterial
nuisance.
During the 2006 heat waves, at least 114 mostly
shallow lakes and ponds in The Netherlands suffered
heavily from cyanobacterial blooms. One of the
seriously affected sites was Lake Gooimeer, a
2,576 ha shallow lake in The Netherlands, which
includes a harbor (Almere-Haven) and a bathing area
at the northern part of the lake. From August 2006
until the end of October 2006, a major cyanobacterial
bloom caused fish kills and foul odors. As a conse-
quence of this bloom, a swimming ban followed, the
harbor was closed and the start and finish of the
European Championship Triathlon had to be relocated
to elsewhere. Following the 2006 heat-waves, many,
mostly commercial, parties claimed to have Colum-
bus’s egg to alleviate these undesirable cyanobacteria
blooms. One of the most heavily promoted products
was ‘‘Effective-Microorganisms’’ (EM) in so-called
‘‘mudballs’’ or ‘‘Bokashi-balls’’. They are based on
the concept of Higa (1998) that addition of EM
would change the microbial community towards
dominance of beneficial species, while suppressing
harmful bacteria. Subsequently, EM-mudballs are
claimed to wipe out cyanobacterial blooms, thereby
making the infested waters clear again (http://www.
emvereniging.nl accessed on June 28, 2008). The
manufacturers intended to apply 12,000 EM-mudballs
in Almere-Haven (The Netherlands). However, the
authorities forbid the application of EM-mudballs
because they contain heavy metals such as mercury as
well as nutrients (Rijkswaterstaat, 2007). Moreover,
the statements and claims about effectiveness were
based on anecdotal evidence rather than on scientifi-
cally defensible evidence. In this study, we tested the
claim that EM-mudballs would suppress and remove
cyanobacteria from infested water in controlled
experiments.
Materials and methods
EM-mudballs and phosphorus release
The EM-mudballs were obtained from Agriton BV
(Noordwolde, The Netherlands) and belonged to a
batch of 12,000 EM-mudballs that were made with
the intention of applying in Almere-Haven (The
Netherlands). Almere-Haven consists of two harbors,
each one has the size of 4 ha (mean depth 1.9 m, max
depth 3 m) that had suffered from major Microcystis
blooms in 2006. The EM-mudballs had an average
fresh weight of ±300 g (A. de Puisselaar, B. V.
Agriton, personal communication). The suggested
dose was 1 ball per m2, which makes maximum in
situ concentrations of 0.1–0.3 g l-1.
To get an estimate of the potential release of phosphate
from EM-mudball material, 0.5 g EM-mudball material
was brought into 100 ml nanopure water in triplicate.
Three additional Erlenmeyer’s only contained 100 ml
nanopure water. The Erlenmeyer’s were closed with
Parafilm and placed for 48 h in an incubator in darkness
at 22C, and continuous orbital shaking (200 rpm).
After this, the material was centrifuged for 5 min at
3,000 rpm, followed by filtration over a 0.45-lm
membrane filter. The filtrates were analyzed on soluble
P as molybdate reactive phosphorus (Murphy & Riley,
1962) using a SKALAR auto-analyzer.
Cyanobacterial scum material was harvested from
Almere-Haven (The Netherlands) on August 16th and
28th 2007. The collected material was counted under
a NIKON light microscope using a Burker Chamber
and subjected to fluorescence analysis for estimating
the contribution of major algal groups, i.e., cyano-
bacteria, chlorophytes, and diatoms to the overall
chlorophyll-a (Chl-a) concentration using a PHYTO-
PAM (Lu¨rling & Verschoor, 2003). It revealed that
the field material consisted of [95% M. aeruginosa
(mostly present in large colonies) and some M. flos-
aquae, Anabaena sp. and 2.5% chlorophytes. Pseud-
oanabaena sp. and Navicula sp. were present on the
mucus of Microcystis colonies, but diatoms did not
show up in the PHYTO-PAM signal.
Effect of EM-mudball material on cyanobacteria
in artificial medium
In the first experiment, cyanobacterial scum material
was inoculated in 400-ml beakers that contained
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