Microcystins do not provide anti-herbivore defence against mixotrophic flagellates

Wilken, Susanne; Wiezer, S.M.H.; Huisman, Jef; Donk, Ellen Van

doi:10.3354/ame01395

Cited by 40 publications

(39 citation statements)

References 43 publications

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“…The mixotroph feeds upon the autotroph with a Holling type III functional response, in 138 accordance with the experimental data of Wilken et al (2010): 139…”

Section: Theory 99supporting

confidence: 80%

Biological control of toxic cyanobacteria by mixotrophic predators: an experimental test of intraguild predation theory

Wilken

Verspagen

Naus‐Wiezer

et al. 2014

Ecological Applications

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Intraguild predators both feed on and compete with their intraguild prey. In theory, intraguild predators can therefore be very effective as biological control agents of intraguild prey species, especially in productive environments. We investigated this hypothesis using the mixotrophic chrysophyte Ochromonas as intraguild predator and the harmful cyanobacterium Microcystis aeruginosa as its prey. Ochromonas can grow photoautotrophically, but can also graze efficiently on Microcystis. Hence, it competes with its prey for inorganic resources. We developed a mathematical model and parameterized it for our experimental food web. The model predicts dominance of Microcystis at low nutrient loads, coexistence of both species at intermediate nutrient loads, and dominance of Ochromonas but a strong decrease of Microcystis at high nutrient loads. We tested these theoretical predictions in chemostat experiments supplied with three different nitrogen concentrations. Ochromonas initially suppressed the Microcystis abundance by >97% compared to the Microcystis monocultures. Thereafter, however, Microcystis gradually recovered to ∼20% of its monoculture abundance at low nitrogen loads, but to 50–60% at high nitrogen loads. Hence, Ochromonas largely lost control over the Microcystis population at high nitrogen loads. We explored several mechanisms that might explain this deviation from theoretical predictions, and found that intraspecific interference at high Ochromonas densities reduced their grazing rates on Microcystis. These results illustrate the potential of intraguild predation to control pest species, but also show that the effectiveness of their biological control can be reduced in productive environments.

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“…The mixotroph feeds upon the autotroph with a Holling type III functional response, in 138 accordance with the experimental data of Wilken et al (2010): 139…”

Section: Theory 99supporting

confidence: 80%

Biological control of toxic cyanobacteria by mixotrophic predators: an experimental test of intraguild predation theory

Wilken

Verspagen

Naus‐Wiezer

et al. 2014

Ecological Applications

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“…However, no induction of toxins was found in response to direct and indirect exposure to the mixotrophic flagellate Ochromonas sp. (Wilken et al, 2010).…”

Section: Chemical Defences In Phytoplanktonmentioning

confidence: 99%

Induced defences in marine and freshwater phytoplankton: a review

2010

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Many organisms have developed defences to avoid predation by species at higher trophic levels. The capability of primary producers to defend themselves against herbivores affects their own survival, can modulate the strength of trophic cascades and changes rates of competitive exclusion in aquatic communities. Algal species are highly flexible in their morphology, growth form, biochemical composition and production of toxic and deterrent compounds. Several of these variable traits in phytoplankton have been interpreted as defence mechanisms against grazing. Zooplankton feed with differing success on various phytoplankton species, depending primarily on size, shape, cell wall structure and the production of toxins and deterrents. Chemical cues associated with (i) mechanical damage, (ii) herbivore presence and (iii) grazing are the main factors triggering induced defences in both marine and freshwater phytoplankton, but most studies have failed to disentangle the exact mechanism(s) governing defence induction in any particular species. Induced defences in phytoplankton include changes in morphology (e.g. the formation of spines, colonies and thicker cell walls), biochemistry (such as production of toxins, repellents) and in life history characteristics (formation of cysts, reduced recruitment rate). Our categorization of inducible defences in terms of the responsible induction mechanism provides guidance for future work, as hardly any of the available studies on marine or freshwater plankton have performed all the treatments that are required to pinpoint the actual cue(s) for induction. We discuss the ecology of inducible defences in marine and freshwater phytoplankton with a special focus on the mechanisms of induction, the types of defences, their costs and benefits, and their consequences at the community level.

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“…Previous studies have reported as possible grazers of Microcystis: protists (Cole and Wynne 1974;Dryden and Wright 1987), rotifers (Snell 1980;Fulton and Paerl 1987), crustacean zooplankton (Hanazato and Yasuno 1984;Jarvis et al 1987), and fish (Moriarty 1973;Kawanabe and Mizuno 1989;Miura 1990). There are only a limited number of rotifers, crustaceans, and fish that graze on Microcystis, but various protistan species have been shown to do so (Zhang et al 1996;Nishibe et al 2002Nishibe et al , 2004Kim et al 2006;Wilken et al 2010). Thus, it is possible that the wax and wane of a Microcystis bloom are dependent on grazing by protists.…”

Section: Introductionmentioning

confidence: 93%

Grazing on Microcystis (Cyanophyceae) by testate amoebae with special reference to cyanobacterial abundance and physiological state

et al. 2010

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We examined the growth of testate amoebae preying on Microcystis whose physiological states were different in laboratory experiments and a hypertrophic pond. We prepared three experimental systems using water samples dominated by Microcystis aeruginosa: light incubation (control), dark incubation (dark), and light incubation with addition of nitrogen and phosphorus (?NP). In all the systems, the colony density of M. aeruginosa decreased slightly during incubation. Physiological activity of phytoplankton as determined by chlorophyll fluorescence was high and almost constant in the control and ?NP systems, whereas it decreased in the dark system. Cell densities of testate amoebae increased in the control and ?NP systems, whereas in the dark system they remained low. Thus, growth of the amoebae was low in the systems where physiological activity of Microcystis was low. In a hypertrophic pond, cell density of testate amoebae increased and remained high when M. aeruginosa predominated. Cell density of testate amoebae increased remarkably, simultaneously with the increases in M. aeruginosa colony density and phytoplankton physiological activity. We also found a significant correlation between densities of M. aeruginosa colonies and testate amoebae. We suggested that the physiological activity of Microcystis is one important factor affecting the growth of testate amoebae grazing on Microcystis.

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Microcystins do not provide anti-herbivore defence against mixotrophic flagellates

Cited by 40 publications

References 43 publications

Biological control of toxic cyanobacteria by mixotrophic predators: an experimental test of intraguild predation theory

Biological control of toxic cyanobacteria by mixotrophic predators: an experimental test of intraguild predation theory

Induced defences in marine and freshwater phytoplankton: a review

Grazing on Microcystis (Cyanophyceae) by testate amoebae with special reference to cyanobacterial abundance and physiological state

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