toxin production and non-toxin-producing strains of cyanobacteria, Microcystis
aeruginosa and Microcystis panniformis, respectively, on different strains of
Chlorophyta, Monoraphidium convolutum and Scenedesmus acuminatus. The
results showed inhibitory effects of both cyanobacterial strains on both green algae
and different strains of green algae exhibited differential sensitivity.
Diatoms are another important phytoplankton group which comprise about 25%
of the world’s net primary production and are essential to several biogeochemical
cycles [25, 26]. Several studies indicate allelopathic effect of cyanobacteria on
diatoms. Schagerl et al. [27] found three cyanobacterial strains, Anabaena torulosa
and two Nostoc strains that allelopathically inhibited the growth of a naturally cooccurring diatom strain, Fragilaria sp., through agar diffusion tests. The sensitivity
of diatoms varied depending on the donor species, the acting chemicals, and the
diatom species. Wang et al. [28] could show that M. aeruginosa cells can have severe
inhibitory effects on the target diatom Cyclotella sp. during their exponential growth
phase. Repeated addition of cyanobacterial culture filtrates showed the strongest
impacts on the diatom Thalassiosira sp. as compared to single additions [29].
Cryptophytes were also found to be affected by cyanobacterial allelochemicals.
Suikkanen et al. [29] tested three cyanobacterial species (Nodularia spumigena,
Aphanizomenon flos-aquae, and Anabaena lemmermannii) and found inhibitory
effects on the cryptophyte Rhodomonas sp. for all. In subsequent studies, they
found that not the hepatotoxin nodularin but unknown metabolites from the cyanobacterium Nodularia spumigena inhibited the growth of the cryptophyte species
(Rhodomonas sp.) from the same habitat [21, 30]. Similar inhibitory effects were
also found in a system including Microcystis aeruginosa (cyanobacteria) and
Cryptomonas ovata; the Cryptophyta was heavily inhibited by M. aeruginosa with
living cells showing the strongest effect [31].
Cyanobacterial species are also inhibited by other co-occurring cyanobacteria by
producing and releasing inhibitory metabolites [32]. Keating [2] found that, in most
cases, the dominant cyanobacterial species in a pond allelopathically inhibited their
cyanobacterial predecessors and promoted their cyanobacterial successors. Microcystis
sp. can affect the cell differentiation of the filamentous cyanobacterial genus Trichormus by decreasing their heterocyst and akinete forming [33]. The genus Trichormus also allelopathically inhibited several cyanobacterial strains, and this
inhibitory effect was mostly stronger than that of Chlorophyta species tested [34].
The genus Nostoc is a filamentous and nitrogen-fixation group of cyanobacteria with
published allelopathic abilities [35]. Schagerl et al. [27] documented strong allelopathic
effects of Nostoc sp. on strains of Anabaena and Microcystis. Strains of filamentous
Oscillatoria were documented to produce bioactive metabolites cyclic peptides
portoamide A which inhibited the growth of Cylindrospermopsis raciborskii [36].
2.2
Effects on Other Aquatic Organisms
Secondary metabolites of cyanobacteria have also been shown to directly or indirectly influence other, non-phototrophic organisms of the aquatic food web. Events
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Y. Pei et al.
aeruginosa and Microcystis panniformis, respectively, on different strains of
Chlorophyta, Monoraphidium convolutum and Scenedesmus acuminatus. The
results showed inhibitory effects of both cyanobacterial strains on both green algae
and different strains of green algae exhibited differential sensitivity.
Diatoms are another important phytoplankton group which comprise about 25%
of the world’s net primary production and are essential to several biogeochemical
cycles [25, 26]. Several studies indicate allelopathic effect of cyanobacteria on
diatoms. Schagerl et al. [27] found three cyanobacterial strains, Anabaena torulosa
and two Nostoc strains that allelopathically inhibited the growth of a naturally cooccurring diatom strain, Fragilaria sp., through agar diffusion tests. The sensitivity
of diatoms varied depending on the donor species, the acting chemicals, and the
diatom species. Wang et al. [28] could show that M. aeruginosa cells can have severe
inhibitory effects on the target diatom Cyclotella sp. during their exponential growth
phase. Repeated addition of cyanobacterial culture filtrates showed the strongest
impacts on the diatom Thalassiosira sp. as compared to single additions [29].
Cryptophytes were also found to be affected by cyanobacterial allelochemicals.
Suikkanen et al. [29] tested three cyanobacterial species (Nodularia spumigena,
Aphanizomenon flos-aquae, and Anabaena lemmermannii) and found inhibitory
effects on the cryptophyte Rhodomonas sp. for all. In subsequent studies, they
found that not the hepatotoxin nodularin but unknown metabolites from the cyanobacterium Nodularia spumigena inhibited the growth of the cryptophyte species
(Rhodomonas sp.) from the same habitat [21, 30]. Similar inhibitory effects were
also found in a system including Microcystis aeruginosa (cyanobacteria) and
Cryptomonas ovata; the Cryptophyta was heavily inhibited by M. aeruginosa with
living cells showing the strongest effect [31].
Cyanobacterial species are also inhibited by other co-occurring cyanobacteria by
producing and releasing inhibitory metabolites [32]. Keating [2] found that, in most
cases, the dominant cyanobacterial species in a pond allelopathically inhibited their
cyanobacterial predecessors and promoted their cyanobacterial successors. Microcystis
sp. can affect the cell differentiation of the filamentous cyanobacterial genus Trichormus by decreasing their heterocyst and akinete forming [33]. The genus Trichormus also allelopathically inhibited several cyanobacterial strains, and this
inhibitory effect was mostly stronger than that of Chlorophyta species tested [34].
The genus Nostoc is a filamentous and nitrogen-fixation group of cyanobacteria with
published allelopathic abilities [35]. Schagerl et al. [27] documented strong allelopathic
effects of Nostoc sp. on strains of Anabaena and Microcystis. Strains of filamentous
Oscillatoria were documented to produce bioactive metabolites cyclic peptides
portoamide A which inhibited the growth of Cylindrospermopsis raciborskii [36].
2.2
Effects on Other Aquatic Organisms
Secondary metabolites of cyanobacteria have also been shown to directly or indirectly influence other, non-phototrophic organisms of the aquatic food web. Events
326
Y. Pei et al.