cyanobacterial species inhibited their immediate predecessor but stimulated their
successor [2].
Allelopathic effects of cyanobacteria certainly also depended on the sensitivity of
the target organism. Different organisms exhibited various responses to different
cell-free filtrates of cyanobacterial donors or their allelochemicals [29, 32, 43]. In
principle, phytoplankton has been shown to develop local genetic adaptation to
external stress such as grazing pressure [116]; however, for allelopathy, this has
not yet been shown [117]. The presence of another competitor can also affect the
sensitivity of cyanobacteria to allelochemicals. Chang et al. [118] tested whether M.
aeruginosa, known to be sensitive to polyphenolic allelochemicals, remains
suppressed when interacting with the less sensitive green alga Desmodesmus
armatus. Interaction with the green alga turned the inhibiting effect of
allelochemicals on the cyanobacterium into an enhancement resulting in increased
growth rates and an increasing abundance of the cyanobacterium under
allelochemical presence. Microcystis species decreased their microcystin production
under the presence of cylindrospermopsin, an allelochemical released from other
strains of cyanobacteria [119]. Pei et al. [120] tested allelopathic effects of Microcystis sp. on a common green alga under the influence of the macrophyte
allelochemical, N-phenyl-2-naphthylamine (PNA). Allelopathic effects on the
green alga were stimulated by PNA.
4.2
Abiotic Factors
The growth of phototrophs is influenced by several physicochemical conditions,
including light, temperature, pH, and nutrient availability. Each cyanobacterial
species or even strain has specific optimum requirements, and deviations from
these will result in impaired growth with potential consequences for allelochemical
production and release.
High water temperatures (above 25
C) are considered to accelerate
cyanobacterial bloom formation. Although the average optimal temperature of
cyanobacteria species has no conspicuous difference to that of green algae [121],
specific optimal values in various cyanobacteria in combination with other properties
such as their buoyancy might contribute to their dominance. Field research has
demonstrated that cyanobacterial blooms and the species succession were highly
related to water temperature [122]. Several species outcompeted others under higher
temperatures [123] and this phenomenon could be related to the toxin release of
specific species. Ma et al. (2015) indicated that an increased water temperature will
favor the bloom by toxic cyanobacteria [113]. For some cyanobacterial species,
higher water temperatures supported the toxic strain rather than non-toxic strain
despite higher growth rates of the non-toxic strain [124]. Hirata et al. (2003) could
show that the release of a putative allelochemical (nostocine A) was enhanced by
higher temperature, and this chemical showed strong toxic effects on green algae
[102].
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Y. Pei et al.
successor [2].
Allelopathic effects of cyanobacteria certainly also depended on the sensitivity of
the target organism. Different organisms exhibited various responses to different
cell-free filtrates of cyanobacterial donors or their allelochemicals [29, 32, 43]. In
principle, phytoplankton has been shown to develop local genetic adaptation to
external stress such as grazing pressure [116]; however, for allelopathy, this has
not yet been shown [117]. The presence of another competitor can also affect the
sensitivity of cyanobacteria to allelochemicals. Chang et al. [118] tested whether M.
aeruginosa, known to be sensitive to polyphenolic allelochemicals, remains
suppressed when interacting with the less sensitive green alga Desmodesmus
armatus. Interaction with the green alga turned the inhibiting effect of
allelochemicals on the cyanobacterium into an enhancement resulting in increased
growth rates and an increasing abundance of the cyanobacterium under
allelochemical presence. Microcystis species decreased their microcystin production
under the presence of cylindrospermopsin, an allelochemical released from other
strains of cyanobacteria [119]. Pei et al. [120] tested allelopathic effects of Microcystis sp. on a common green alga under the influence of the macrophyte
allelochemical, N-phenyl-2-naphthylamine (PNA). Allelopathic effects on the
green alga were stimulated by PNA.
4.2
Abiotic Factors
The growth of phototrophs is influenced by several physicochemical conditions,
including light, temperature, pH, and nutrient availability. Each cyanobacterial
species or even strain has specific optimum requirements, and deviations from
these will result in impaired growth with potential consequences for allelochemical
production and release.
High water temperatures (above 25
C) are considered to accelerate
cyanobacterial bloom formation. Although the average optimal temperature of
cyanobacteria species has no conspicuous difference to that of green algae [121],
specific optimal values in various cyanobacteria in combination with other properties
such as their buoyancy might contribute to their dominance. Field research has
demonstrated that cyanobacterial blooms and the species succession were highly
related to water temperature [122]. Several species outcompeted others under higher
temperatures [123] and this phenomenon could be related to the toxin release of
specific species. Ma et al. (2015) indicated that an increased water temperature will
favor the bloom by toxic cyanobacteria [113]. For some cyanobacterial species,
higher water temperatures supported the toxic strain rather than non-toxic strain
despite higher growth rates of the non-toxic strain [124]. Hirata et al. (2003) could
show that the release of a putative allelochemical (nostocine A) was enhanced by
higher temperature, and this chemical showed strong toxic effects on green algae
[102].
336
Y. Pei et al.