CYANOBACTERIAL TOXINS - Cyanobacteria - page 563

lowland rivers of Main Berlin waterways that are connected to some shallow lakes. The surface
waters of this ecosystem are measured for concentrations of MCs (both cellular and extracellular),
as measured by ELISA assay, varied between 0.14 and 119 µg L -1 . Nearly 74% of the samples showed
MC values above 1 µg L -1 whereas 38% of the samples revealed MC content of 10 µg L -1 . Nearly 2%
of the samples exhibited MC values of 100 µg L -1 . On the other hand, anatoxin-a levels of two Berlin
Lakes Unterhavel and Mueggelsee were 0.01 µg L -1 (Fromme et al ., 2000).
The periodicity, species composition and MC concentration in 18 eutrophic Czech reservoirs
were studied over a period of two years. The prevalence of toxic cyanobacterial blooms increased
in the month of August with a shift in species predominance to Microcystis spp. 90% of the samples
contained MCs and three MC variants (MC-LR, MC-RR and MC-YR) have been detected. The
concentration of MCs was positively correlated with chlorophyll a and cyanobacterial biovolume.
This study signifi es the potential health risk to human population and the need to regularly monitor
the development of toxic blooms (Znachor et al ., 2006). A survey conducted over a period of 13 years
(1987 to 2000) in the Greek freshwater lakes, toxic blooms of Microcystis , Anabaena , Anabaenopsis ,
Aphanizomenon and Cylindrospermopsis were represented in 9 out of 33 lakes. The concentration of
MC ranged from 50.3 to 1638 ± 464 µg g -1 . Lake Kastorea was chosen for studying seasonal variations
of the cyanobacteria and the biovolume of the cyanobacteria was quite high (11 µL L -1 ) throughout
the year that was in excess of the levels proposed by WHO for recreational and drinking waters.
Intracellular MC-LR concentrations of the blooms reached as high as 3186 µg L -1 during September
to November thus posing a very high risk to human beings (Cook et al ., 2004). Lakes Lysimachia and
Trichoonis in Greece supported the development of toxic blooms of Aph . ovalisporum constituting
99 and 58% of the total biomass, respectively. The concentration of MC-LR in Lake Lysimachia was
0.9 µg L -1 (Gkelis et al ., 2005). Strains of Aph . ovalisporum from Israel and Australia are reported to
produce CYN (Banker et al ., 1997; Shaw et al ., 1999). MC content of Microcystis blooms from Belgium
was 556 µg g -1 dry weight (Wirsing et al ., 1998). A taxonomic and morphological description of 21
cyanobacterial blooms from Belgium were presented along with their geographical distribution
(Willame and Hoffmann, 1999). Blooms of Microcystis and Planktothrix were represented in almost
all the 64 samples collected from southern part of Belgium and in Luxemberg as well as in bordering
northeastern France followed by the genera Anabaena , Woronichinia and Aphanizomenon . MCs were
found in 53% of the blooms and were mainly due to the preponderance of Microcystis but highest
concentration of 2331 µg g -1 dry weight was found in a sample dominated by Woronichinia naegeliana
(Fig. 2F; Willame et al ., 2005).
The genetic diversity of 107 Microcystis colonies (seven morphospecies) from 15 European
Lakes was characterized on the basis of 16S rRNA gene ITS diversity. These studies eanabled
the recognition of 59 distinct classes and suggested that there exists a significant genetic
variation within and across habitats. This is supported by the fact that 93% of the population of
M . aeruginosa consisted of two distinct classes whereas 24% of the population exhibited 14 classes
found in two different lakes with one group being represented in lake across Czech Republic,
Germany, Italy and Scotland. Thus the genetic heterogeniety of M . aeruginosa may have major
ecological impact (Janse et al ., 2004).
Toxic cyanobacterial blooms of Microcystis , Aphanizomenon and Anabaena have been recorded
along the Guadiana River (southwestern Spain) at different sites where the MC concentrations
ranged from 0.10-21.86 MC-LR equivalent L -1 . Lakes Lysimachia and Trichonis in Greece supported
the development of toxic blooms of Aph . ovalisporum constituting 99 and 58% of the total biomass,
respectively. The concentration of MC-LR in Lake Lysimachia was 0.9 µg MC-LR equivalent L -1 in
a site (Valdelacalzada) and 0.1 to 11.3 µg MC-LR equivalent L -1 at another site (Vitonogales). These