37T. Eleršek: First report of cyanobacterial bloom of Microcystis viridis (A. Braun) Lemmermann in Slovenia
 ACTA BIOLOGICA SLOVENICA 
 LJUBLJANA 2009             Vol. 52, [t. 1: 37–47
Sprejeto (accepted): 24. 07. 2009
First report of cyanobacterial bloom of Microcystis viridis (A. Braun) 
Lemmermann in Slovenia
Prvi opis cvetenja cianobakterije Microcystis viridis (A. Braun) 
Lemmermann v Sloveniji
Tina eleršek
National Institute of Biology, Večna pot 111, 10001 Ljubljana, Slovenia
Fax number: +3861 2412980
E-mail address: tina.elersek@nib.si
Abstract. The presence of the cyanobacterial bloom of Microcystis viridis (A. Braun) 
Lemmermann is reported for the first time in Slovenia. After field sampling, and detailed micro-
scopic observations, species analysis, chlorophyll content analysis, and cyanobacterial cyclic 
peptides were determined, the latter by high performance liquid chromatography (HPLC). Cells 
were found in colonies with limited amounts of more or less refractive mucilage. The average 
diameter of a cell was 4–7 µm. Three microcystins, two anabaenopeptins and planktopeptin BL 
1125, were identified. The content of cyclic peptides in the bloom was in the range of 2.3–6.6 
mg g–1 of cellular dry weight. M. viridis was dominant in the cyanobacterial bloom, other species 
being Micorcystis wesenbergii, Microcystis aeruginosa, Anabaena flos-aque, Anabaena spiralis, 
Aulacoseira granulata, Closterium sp., Euglena sp., Pediastrum duplex, Scenedesmus quadri-
cauda, Staurastrum gracile, Trachelomonas volvocina, Trachelomonas hispida and Tetraedron 
limneticum. In keeping with previous studies the content of cyclic peptides in the cyanobacterial 
bloom was high enough to cause bloom lysis. This fact was also confirmed by field observation; 
not only bloom composition change, but after 8 days there was no visible cyanobacterial bloom 
on the Boreci reservoir surface, although no heavy rain or wind was observed during this period. 
The discovery of M. viridis bloom in Slovenia is very important, since toxic bloom constitutes 
a threat all over the World.
Key words. cyanobacteria, cyanobacterial bloom, Microcystis viridis, microcystin, cyclic 
peptides
Izvleček. V Sloveniji prvič poročamo o prisotnosti cianobakterijskega cveta Microcystis 
viridis (A. Braun) Lemmermann. Po vzorčenju, temeljitem mikroskopskem pregledu, analizi 
vrstnega sestava in analizi vsebnosti klorofila smo določili prisotnost cianobakterijskih cikličnih 
peptidov s pomočjo tekočinske kromatografije visoke ločljivostji (HPLC). Celice so v kolonijah 
obdane z sluzjo, ki lomi svetlobne žarke. Povprečni premer celic je bil 4–7 µm. Identificirali smo 
tri mikrocistine, dva anabaenopeptina in planktopeptin BL 1125. Vsebnost cikličnih peptidov v 
cvetu je bila 2.3–6.6 mg g–1 suhe celične mase. V cianobakterijskem cvetu je prevladovala vrsta 
M. viridis, ostale vrste pa so bile Micorcystis wesenbergii, Microcystis aeruginosa, Anabaena 
flos-aque, Anabaena spiralis, Aulacoseira granulata, Closterium sp., Euglena sp., Pediastrum 
duplex, Scenedesmus quadricauda, Staurastrum gracile, Trachelomonas volvocina, Trachelomo-
nas hispida in Tetraedron limneticum. Na podlagi rezultatov prejšnjih raziskav lahko zaključimo, 
da je vsebnost cikličnih peptidov dovolj visoka, da lahko povzroči lizo cveta. To dejstvo je bilo 
potrjeno tudi z opazovanji v naravnem okolju v okviru te raziskave. Ni prišlo samo do spremembe 
38 Acta Biologica Slovenica, 52 (1), 2009
vrstne sestave cveta, temveč do izginotja cianobakterijskega cveta na površini jezera Boreci 
po osmih dneh, čeprav v tem obdobju ni bilo močnega deževja, niti vetra. Odkritje pojavljanja 
cvetenja M. viridis v Sloveniji je izrednega pomena, saj strupen cianobakterijski cvet predstavlja 
grožnjo po celem svetu.
Ključne besede. cianobakterije, cianobakterijski cvet, Microcystis viridis, mikrocistin, 
ciklični peptidi
Introduction
About 60 % of cyanobacterial samples in-
vestigated worldwide contain toxins (guidelineS 
2003). The toxicity of a single bloom can, how-
ever, change in both time and space. Demonstra-
tion of toxicity of the cyanobacterial population 
in a given lake or reservoir does not necessarily 
imply an environmental or human hazard as long 
as the cells remain thinly dispersed. Mass devel-
opments and, especially, surface scums pose the 
major risk. 
Microcystis has been known to be the major 
genus among the cyanobacteria to cause blooms 
in fresh waters worldwide (CarmiCHael 1992; 
guidelineS 2003). Microcystis blooms frequently 
occur in the eutrophic waters. In many north-
eastern Slovenian lakes and reservoirs, nutrient 
loading, coupled with year-round warm weather, 
favours the growth of cyanobacteria, several 
of which can produce cyanotoxins, especially 
the potent genotoxins (Žegura & al. 2003) and 
liver toxins called microcystins (MC). The tox-
ins are of interest due to their threat to humans 
and animals (CarmiCHael 1994; falConer & al. 
1994, 1999).
M. viridis has been found in Finnish fresh 
and coastal waters (e.g. Sivonen & al. 1990), a 
Swedish lake (Cronberg & al. 1999), a Brazilian 
reservoir (figueredo & giani 2001), China (Song 
& al. 1998) and Japan (kameyama & al. 2004). 
Based on 16S rRNA analyses of M. viridis (lePre 
& al. 2000) and DNA-DNA homology analysis 
(kondo & al. 2000), some authors (otSuka & 
al. 2001), under the rules of the bacteriological 
code, propose the unification of five species of 
Table 1: Isolated peptides from cyanobacteria Microcystis viridis.
Microcystis viridis strain isolated peptides reference
M. viridis cyanoviridin-RR Kusumi et al., 1987
M. viridis NIES-102 cyanoviridin-RR Ooi et al., 1989
M. viridis microcystin-RR, -YR, -LR Watanabe et al., 1989
M. viridis NIES-102 mikroviridin Ishitsuka et al., 1990
M. viridis - axenic microcystin-RR, -YR, -LR, -LA Kaya & Watanabe, 1990
M. viridis – from bloom microcystin-RR, -LR Kaya & Watanabe, 1990
M. viridis NIES-102 hepatotoxic polypeptides Yusamo & Sugaya, 1991
M. viridis NIES-102 aeruginosin 102-A, 102-B Matsuda et al., 1996
M. viridis NIES-103 micropeptin 103 Murakami et al., 1997
M. viridis NIES-103 aeruginosin 103-A Kodani et al., 1998
M. viridis– from bloom microcystin-RR Song et al., 1998
M. viridis NIES-102 polypeptide MVL Yamaguchi et al., 1999
M. viridis NIES-102 microcystin-RR, -YR, -LR Kameyama et al., 2002, 2004
M. viridis FACHB cyclic peptides with mcyB gene Pan et al., 2002
39T. Eleršek: First report of cyanobacterial bloom of Microcystis viridis (A. Braun) Lemmermann in Slovenia
cyanobacterial genus Microcystis: M. aeruginosa, 
M. ichthyoblabe, M novacekii, M. viridis and 
M. wesenbergii. It has been recommended that 
attention should be paid to the occurrence and 
possibility of toxic blooms of M. viridis from 
the standpoint of water management and public 
health (Watanabe & al. 1986).
Peptides from M. viridis do not differ com-
pletely from other peptides from genus Micro-
cystis (Table 1). Some M. viridis peptides are 
known to be active as essential intracellular 
nitrogen compounds in toxic cyanobacteria, 
substances active against grazing zooplankton 
(yaSuno & Sugaya 1991), a chymotrypsin in-
hibitor (murakami & al. 1997) and as a mannan-
binding lectin important for haemagglutination 
(yamaguCHi & al. 1999). Nevertheless, not much 
more is known about peptides from M. viridis 
and there is no report to date of M. viridis bloom 
occurrence in Slovenia.
Material and methods
Field sampling
Three sampling points were located in the 
north-eastern part of Slovenia. Gauss Krüger 
coordinates for reservoir Boreci (Križevci village) 
are y = 588239.7; x = 158373,3; z = 182m. For 
reservoir Podgrad (Podgrad village) y = 574341.4; 
x = 171416; z = 208m. For reservoir Hotinja vas 
(Hotinja village) y = 552400.4; x = 147283.2; z 
= 262m. The majority of results presented in this 
article are from reservoir Boreci, since the most 
extensive analyses were performed there. Samples 
were collected with the planktonic net, separately 
from the whole water column and surface scum.
Cyanobacterial and algal species 
Species were identified using an inverted 
microscope according to komarek (1991, 1999–
2000), StarmaCH (1966) and Hindak (1978). The 
abundance on August the 9th was estimated with 
several dilutions of original sample and count-
ing with haemocytometer. Samples from other 
dates did not show dominance of one, but four 
species, and the abundance with counting could 
not be estimated precisely enough (symbol + in 
Table 2). Samples were analysed for composition 
of plankton species and taxonomic determination 
under an inverted microscope (Nikon Eclipse 
TE300). Cells were measured with Lucia (System 
for Image Processing and Analysis LUCIA 4.6, 
Laboratory Imaging Ltd.). 
Chlorophyll content analysis
Chlorophyll a was measured by methanol ex-
traction according to vollenWeider (1969) with 
a spectrophotometer UV-2101 PC (Shimadzu). 
The procedure was modified to filtration of 10 
ml samples in triplicate.
Cyanobacterial cyclic peptide analysis
The lyophilised bloom material was proc-
essed according to Harada & al. (1988) with 
minor modifications. Dried cyanobacteria (1000 
mg) were extracted three times with 5% aqueous 
acetic acid (3 x 20 ml) for 30 min with stirring. 
The extracts were centrifuged at 4000 rpm for 10 
min. The combined supernatants were applied to 
preconditioned 500 mg reversed-phase dispos-
able columns (LiChrolut RP-18, Merck). The 
columns containing the extract were washed with 
20 ml of 10 % methanol and the cyclic peptides 
eluted with 2 ml methanol (LiChrosolv, Merck), 
evaporated to dryness under nitrogen stream and 
the residues dissolved in 0.05 M phosphate buffer, 
pH 3. Samples were analysed by HPLC, using 
isocratic elution with methanol: phosphate buffer 
48:52 (v/v). The HPLC/PDA equipment consisted 
of a Waters 600 Controller, Waters 616 pump and 
Waters PDA Detector. Millenium32 software (Ver. 
3.0, Waters) was used to run the hardware and to 
process the data.
Identification and visualization of cyclic pepti-
des with a photodiode array detector
The chromatogram was monitored at four 
wavelength maxima – 238, 225, 220 and 215 
nm – in order to locate and distinguish MC from 
other bioactive cyclic peptides of interest. The 
wavelengths are characteristic of individual cyclic 
peptides; MCs have a characteristic absorption 
at 238 nm, while other isolated cyclic peptides 
have absorption maxima at lower wavelengths. 
The depsipeptide planktopeptin BL1125 was 
detected at 225 nm and anabaenopeptins B and F 
40 Acta Biologica Slovenica, 52 (1), 2009
at 215 nm. Both types of non-toxic cyclic peptide 
have additional characteristic absorption maxima 
at 278–279 nm that were used to confirm the pre-
liminary identification (graCH-PogrebinSky & al. 
2003). The amounts of the cyclic peptides were 
calculated from the individual peaks by compari-
Table 2: Bloom sample structure and dominant species (present in footnote) on two days in August 2006 from 
Boreci reservoir.
Bloom sample structure 9. 8. 2006 Bloom sample structure 17. 8. 2006
+ Microcystis viridis 94 % + Microcystis viridis
Microcystis wesenbergii 4% + Microcystis wesenbergii
Microcystis aeruginosa + Microcystis aeruginosa
Anabaena flos-aque + Anabaena spiroides
Anabaena spiralis Aphanizomenon flos-aque
Aulacoseira granulata Aulacoseira granulata
Closterium sp. Anabaena solitaria
Euglena sp. Woronichinia naegeliana
Pediastrum duplex Dictyosphaerium pulchellum
Scenedesmus quadricauda Euglena sp.
Staurastum gracile Pediastrum duplex
Trachelomonas volvocina Staurastum gracile
Trachelomonas hispida Trachelomonas volvocina
Tetraedron limneticum Trachelomonas hispida
+ = dominating species
Fig. 1: Cyanobacterial bloom in Boreci reservoir, located in Križevci village, 9. 8. 2006, photo: Tina Eleršek.
41T. Eleršek: First report of cyanobacterial bloom of Microcystis viridis (A. Braun) Lemmermann in Slovenia
Fig. 2: Colonies of Microcystis viridis (right side of figure) and Microcystis wesenbergii (indicated by arrows) 
under (A) light and (B) phase contrast microscope, 200 x magnified, from Locality Boreci reservoir, 
9.8.2006, photo: Tina Eleršek.
son of the integrated peak areas with the values 
from calibration curves standardized by previ-
ously isolated cyclic peptides in pure form.
Results and discussion
This is the first report of cyanobacterial bloom 
of Microcystis viridis (A. Braun) Lemmermann 
in Slovenia. Microscopic examination of the 
phytoplankton samples showed the dominance 
42 Acta Biologica Slovenica, 52 (1), 2009
Fig. 3: Colonies of Microcystis viridis (right) and Anabaena spiralis (left) under phase contrast microscope, 400 
x magnified, from Locality Boreci reservoir, 9.8.2006, photo: Tina Eleršek.
Fig. 4: Colonies of Microcystis viridis under phase contrast microscope, 600 x magnified, from Locality Boreci 
reservoir, 9.8.2006, photo: Tina Eleršek.
43T. Eleršek: First report of cyanobacterial bloom of Microcystis viridis (A. Braun) Lemmermann in Slovenia
Fig. 5: HPLC chromatogram of Microcystis viridis bloom extract run from a preparative column using isocratic 
elution with methanol: phosphate buffer 50:50 (v/v). The diagrams show the elution pattern monitored 
at three different wavelengths: 215, 225 and 238 nm. MC is clearly visible at the characteristic λmax of 
238 nm, while the other three cyclic peptides are seen only as minor peaks (vertical arrows in the low-
est panel). PP BL, AnP B and AnP F are better detected at lower wavelengths (upper two panels). AnP 
B = anabaenopeptin B; AnP F = anabaenopeptin F; PP = planktopeptin BL 1125, MC = unidentified 
microcystin 
44 Acta Biologica Slovenica, 52 (1), 2009
Fig. 6: The typical absorption spectra of five cyclic peptides from Microcystis viridis bloom at their characteristic 
retention time, marked in the upper part. AnP = anabaenopeptin; PP = planktopeptin BL 1125, MC = uni-
dentified microcystin.
of M. viridis in the bloom in the first half of 
the August in reservoir Boreci (Fig. 1). After 8 
days, M. viridis was found in two neighbour-
ing reservoirs also, Hotinja vas and Podgrad. 
Changes in bloom sample structure were very 
fast; in just 8 days we observed different bloom 
composition (Table 2, Figs. 2 and 3). Cells were 
found in colonies (Fig. 4) with limited, more or 
less refractive mucilage, best seen under phase 
contrast microscopy (e.g. Fig. 2). The average 
diameter of cells was 4–7 µm. The contents of 
chlorophyll a of cyanobacterial bloom from 
Boreci reservoir were similar, 320 µg/l (9.8.2006) 
and 340 µg/l (17.8.2006). HPLC analysis showed 
that M. viridis bloom (from 9.8.2006) contains 
three MC and three non-toxic cyclic peptides, 
two anabaenopeptins and plaktopeptin BL1125 
(Fig. 5), which have important roles in bloom 
lysis (Sedmak & eleršek, 2005, 2006). All the 
cyclic peptides have characteristic absorption 
spectra (Fig. 6). Their content varied in the 
range of 2.3–6.6 mg g–1 of cellular dry weight. 
As found in previous studies (Sedmak & koSi, 
1997; Sedmak & eleršek, 2005, 2006; Sedmak & 
al., 2007), the content of cyclic peptides was high 
enough to cause bloom lysis. Interestingly, this 
fact was confirmed by field observation; bloom 
composition not only changed, but, after 8 days, 
there was no visible cyanobacterial bloom on the 
reservoir surface, although no heavy rain or wind 
was detected during this period. The discovery of 
M. viridis bloom in Slovenia is very important, 
since toxic bloom constitutes a threat all over 
the World.
Conclusion
The presence of the cyanobacterial bloom of 
Microcystis viridis (A. Braun) Lemmermann is 
reported for the first time in Slovenia. Cells were 
found in colonies with refractive mucilage. The 
content of cyclic peptides (three microcystins, 
two anabaenopeptins and planktopeptin BL 1125) 
in the cyanobacterial bloom was high enough to 
cause bloom lysis. This fact was also confirmed 
by field observation. The discovery of M. viridis 
bloom in Slovenia is very important, since toxic 
bloom constitutes a threat all over the World.
Acknowledgements
Special acknowledgements go to Dr. Bojan 
Sedmak for HPLC analyses and determina-
tion of cyclic peptides, to Dr. Gorzd Kosi for 
determination of the bloom sample structure, to 
Karmen Stanič for excellent technical assistance 
and to Prof. Roger Pain for critical reading of 
the manuscript.
45T. Eleršek: First report of cyanobacterial bloom of Microcystis viridis (A. Braun) Lemmermann in Slovenia
Literature
CarmiCHael W.W. 1992: Cyanobacteria secondary metabolites – the cyanotoxins. Journal of Applied 
Bacteriology 72: 445–459.
CarmiCHael W.W. 1994: The toxins of cyanobacteria, Scientific American, 270: 78–86.
Cronberg g., H. annadotter & l.a. laWton 1999: The occurrence of toxic blue-green alge in Lake 
Ringesjön, southern Sweden, despite nutrient reduction and fish biomanipulation. Hydrobiologia 
404 (0): 123–129.
falConer i.r. 1994: Toxicity of the blue-green algae (cyanobacterium) Microcystis aeruginosa in 
drinking water to growing pigs, as an animal model for human injury and risk assesment. Envi-
ronmental Toxicology and Water Quality 9: 131–139.
falConer i.r. 1999: An overview of problems caused by toxic blue-green algae (cyanobacteria) in 
drinking and recreational water. Environmental Toxicology 14, 1: 5–12.
figueredo C.C. &  a. giani 2001: Seasonal variation in the diversity and species richness of phyto-
plankton in a tropical eutrophic reservoir. Hydrobiologia 445 (1–3): 165–174.
graCH-PogrebinSky o., b. Sedmak & S. Carmeli 2003: Protease inhibitors from a Slovenian Lake 
Bled toxic waterbloom of the cyanobacterium Planktothrix rubescens. Tetrahedron 59: 8329–8336.
Guidelines for safe recreational water environments, Volume 1, World Health Organization (WHO), 
2003.
Harada k.i., k. matSuura, m. Suzuki, H. oka, m.f. Watanabe, S. oiSHi, a. daHlem,v.r. beaSely & 
W.W. CarmiCHael 1988: Chemical analyses of toxic peptides produced by cyanobacteria. Journal 
of Chromatography 448: 275–283.
Hindak f., P. marvan, J. komarek, k. roSa, J. PoPovSky & o. lHotSky 1978: Sladkovodne riasy. 
Slovenske pedagogicke nakladatelstvo, Bratislava, 724 pp.
iSHitSuka m.o., t. kuSumi & H. kakiSaWa 1990: Microviridin: a novel tricyclic depsipeptide from toxic 
cyanobacteruim Microcystis viridis. Journal of American chemical society 112: 8180–8182.
kameyama k., n. Sugiura, y. inamori & t. maekaWa 2004: Characteristics of microcystin production 
in the cell cycle of Microcystis viridis. Environmental toxicology 19 (1): 20–25.
kameyama k., n. Sugiura, H. iSoda, y. inamori & t. maekaWa 2002: Effect of nitrate and phosphate 
concentration on production of microcystins by Microcystis viridis NIES-102. Aquatic ecosystem 
health & management 5 (4): 443–449.
kaya k. & m.m. Watanabe 1990: Microcystin composition of an axenic clonal strain M. viridis and M. 
viridis – containing waterbloom in Japanese freshwaters. Journal of Applied Phycology 2 (2): 37–43.
kodani S.,k. iSHida & m. murakami 1998: Aeruginosin 103-A, a thrombin inhibitor from cyanobac-
terium Microcystis viridis. Journal of Natural Products 61: 1046–1048.
komarek J. 1991: A review of water-bloom forming Mycrocystis species with regard to population 
from Japan. Algological studies 64: 115–127.
komarek J.  & k. anagnoStidiS k 1999–2000: Cyanoprokaryota (19). In: Ettl H., Gärtner G., Heynig 
H., Mollenhauer D. (Eds.). Süsswasserflora von Mitteleuropa. Spektrum Akademischer Verlag 
GmbH, Heidelberg, Berlin.
kondo r., t. yoSHida, y. yuki & S. HiroiSHi 2000: DNA-DNA reassociation among a bloom-forming 
cyanobacterial genus, Microcystis. International journal of systematic and evolutionary micro-
biology 50: 767–770.
kuSumi t., t. ooi, m.m. Watanabe & H. takaHaSHi 1987: Cyanoviridin RR, a toxin from the cyano-
bacterium (blue-green alga) Microcystis viridis. Tetrahedron letters.
lePre C., a. Wilmotte & b. meyer 2000: Molecular divertisity of Microcystis strains (Cyanophyceae, 
Chroococcales). Systematic and geography of plants 70: 275–283.
matSuda H., t. okino, m. murakami & k. yamaguCHi 1996: Aeruginosin 102-A and B, new throm-
bin inhibitors from the cyanobacterium Microcystis viridis (NIES-102). Tetrahedron 52 (46): 
14501–14506.
46 Acta Biologica Slovenica, 52 (1), 2009
murakami m., S. kodani, k. iSHida, H. matSuda & k. yamaguCHi 1997: Micropeptin 103, a chy-
motrypsin inhibitor from cyanobacterium Microcystis viridis (NIES-103). Tetrahedron letters 38 
(17): 3035–3038.
ooi t., t. kuSumi, H. kakiSaWa & m.m. Watanabe 1989: Structure of cyanoviridin RR, a toxin from 
the blue-green alga Microcystis viridis. Journal of Applied Phycology 1 (1): 31–38.
otSuka S., S. Suda, S. SHibata, H. oyaizu, S. matSumoto & m.m. Watanabe 2001: A proposal for 
the unification of five species of the cyanobacterial genus Microcystis Kützig ex Lemmermann 
1907 under the Rules of the bacterial code. International Journal of Systematic and Evolutionary 
Microbiology 51: 873–879.
Pan H., l. Song,y. liu & t. börner 2002: Detection of hepatotoxic Microcystis strains by PCR 
with intact cells from both culture and environmental samples. Archives of Microbiology 178: 
421–427.
Sedmak b., S. Carmeli & t.  eleršek 2008: »Non-toxic« cyclic peptides induce lysis of cyanobacte-
ria – an effective cell population density control mechanism in cyanobacterial blooms. Microbial 
Ecology 2 (56): 201–209.
Sedmak b. & t. eleršek 2005: Microcystins induce morphological and physiological changes in 
selected representative phytoplanktons. Microbial Ecology 50: 298–305.
Sedmak b. & t.  eleršek 2006:  Microcystins induce morphological and physiological changes in 
selected representative phytoplanktons. Microbial Ecology 51: 508–515.
Sedmak b. &  g. koSi  1997: Microcystins in Slovene freshwaters (Central Europe) – first report. 
Natural toxins 5: 64–73.
Sedmak b. & g. koSi 1998: The role of microcystins in heavy cyanobacterial bloom formation. Journal 
of Plankton Research 20, 4: 691–708.
Sedmak b. & g. koSi 1998: Erratum. The role of microcystins in heavy cyanobacterial bloom forma-
tion. Journal of Plankton Research 20, 4: 1421.
Sedmak b. & g. koSi 2002: Harmful cyanobacterial blooms in Slovenia – Bloom types and microcystin 
producers. Acta Biologica Slovenica 45: 17–30.
Sedmak b., koSi g. & b. kolar 1994: Cyanobacteria and their relevance. Periodicum Biologorum 
96, 4: 428–430.
Sedmak b. & d. šuPut 2002: Co-operative effects in tumorigenicity. The microcystin example. Ra-
diology and Oncology 36, 2: 162–164.
Sivonen k., S.i. niemelä, r.m.  niemi, l. lePiStö, t.H. luoma & l.a. räSänen 1990: Toxic cyanobac-
teria (blue-green algae) in Finnish fresh and coastal waters. Hydrobiologia 190 (3): 267–275.
Song l., t. Sano, r. li, m.m. Watanabe, y. liu, & k. kaya 1998: Microcystin production of Mi-
crocystis viridis (cyanobacteria) under different culture conditions. Phycological research 46 (2): 
19–23.
StarmaCH k. 1966: Cyanophita-Sinice Glaucophyta-Glaukofity. Flora slodkowodna Polski, Tom 2, 
Warszawa, 807 pp.
vollenWeider r.a. 1969: Primary production in aquatic environments. Internal biology handbook 
12. Oxford, Blackwell Scientific Publications: 225 pp.
Watanabe m.f., k.i. Harada, k. matSuura, m. Watanabe, & m. Suzuki 1989: Heptapeptide toxin 
production during batch culture of two Microcystis species (Cyanobacrteria). Journal of Applied 
Phycology 1 (2): 161–165.
Watanabe m.f., S. oiSHi, y. Watanabe & m. Watanabe 1986: Strong probability of lethal toxicity 
in the blue-green alga Microcystis viridis Lemmermann. Journal of Phycology JPYLAJ 22 (4): 
552–556.
yamaguCHi m., t. ogaWa, k. muramoto, y. kamio, m. Jimbo & H. kamiya 1999: Isolation and 
characterization of a mannan-binding lectin from freshwater cyanobacterium (blue-green algae) 
Microcystis viridis. Biochemical and biophysical research communications 265 (3): 703–708.
47T. Eleršek: First report of cyanobacterial bloom of Microcystis viridis (A. Braun) Lemmermann in Slovenia
yaSuno m. & y. Sugaya 1991: Toxicities of Microcystis viridis and the isolated hepatotoxic polypep-
tides of Cladocerans. Internationale vereinigung fuer theoretishe und engewandte limnologie 
verhandlungen IVTLAP 24 (4): 2622–2626.
yaSuno m., y. Sugaya, k. kaya & m.m. Watanabe 1998: Variations in the toxicity of Microcystis 
sopecies to Moina macrocopa. Phycological research, 46 suppl.: 31–36.
Žegura b., b. Sedmak & m. filiPič 2003: Microcystin-LR induces oxidative DNA damage in human 
hepatoma cell line HepG2. Toxicon 41: 41–48.