Phytoplankton defenses: Do <i>Emiliania huxleyi</i> coccoliths protect against microzooplankton predators?

Strom, Suzanne L.; Bright, Kelley J.; Fredrickson, Kerri A.; Cooney, Elizabeth C.

doi:10.1002/lno.10655

Cited by 7 publications

(8 citation statements)

References 67 publications

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“…For example, Harvey et al (2015) found a negative impact on microzooplankton growth upon consumption of calcified E. huxleyi, which would ultimately result in a decrease in grazing and an increase in E. huxleyi population growth. Further, E. huxleyi has a high level of genetic plasticity (Read et al, 2013), with variability in cell CaCO 3 quotas having bloomlevel impacts (Poulton et al, 2013), and strain-specificity in grazing interactions (Harvey et al, 2015;Strom et al, 2017). Therefore, we cannot discount that coccoliths may provide a protective function during grazing interactions outside of ingestion or that grazer selectivity against particular E. huxleyi strains or morphotypes (or ecotypes) could occur in the natural environment.…”

Section: Discussionmentioning

confidence: 99%

“…Prey selectivity by microzooplankton is mediated by a variety of factors including prey size, morphology, and chemical composition (Tillmann, 2004). Microzooplankton grazing studies on coccolithophores have revealed disparate results, from reduced grazing rates to enhanced grazer preference for calcified E. huxleyi cells (Hansen et al, 1996;Kolb and Strom, 2013;Harvey et al, 2015;Strom et al, 2017). Harvey et al (2015) found that calcified E. huxleyi could slow the growth rate of the dinoflagellate predator, leading to a decline in grazing pressure.…”

Section: Introductionmentioning

confidence: 99%

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The Possession of Coccoliths Fails to Deter Microzooplankton Grazers

et al. 2020

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Phytoplankton play a central role in the regulation of global carbon and nutrient cycles, forming the basis of the marine food webs. A group of biogeochemically important phytoplankton, the coccolithophores, produce calcium carbonate scales that have been hypothesized to deter or reduce grazing by microzooplankton. Here, a meta-analysis of mesocosm-based experiments demonstrates that calcification of the cosmopolitan coccolithophore, Emiliania huxleyi, fails to deter microzooplankton grazing. The median grazing to growth ratio for E. huxleyi (0.56 ± 0.40) was not significantly different among non-calcified nano- or picoeukaryotes (0.71 ± 0.31 and 0.55 ± 0.34, respectively). Additionally, the environmental concentration of E. huxleyi did not drive preferential grazing of non-calcified groups. These results strongly suggest that the possession of coccoliths does not provide E. huxleyi effective protection from microzooplankton grazing. Such indiscriminate consumption has implications for the dissolution and fate of CaCO3 in the ocean, and the evolution of coccoliths.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Possession of Coccoliths Fails to Deter Microzooplankton Grazers

et al. 2020

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“…In the same study, however, the authors found that predators which preyed on non-calcifying genotypes grew faster than those fed with calcified cells (Harvey et al, 2015). Strom et al (2018) compared predation rates of the dinoflagellate Amphidinium longum on calcified relative to naked E. huxleyi prey and found no evidence that the coccosphere prevents ingestion by the grazer. Instead, ingestion rates were dependent on the offered genotype of E. huxleyi (Strom et al, 2018).…”

Section: Introductionmentioning

confidence: 91%

“…Strom et al (2018) compared predation rates of the dinoflagellate Amphidinium longum on calcified relative to naked E. huxleyi prey and found no evidence that the coccosphere prevents ingestion by the grazer. Instead, ingestion rates were dependent on the offered genotype of E. huxleyi (Strom et al, 2018). Altogether, these two studies suggest that the genotype has a strong influence on ingestion by the microzooplankton species, but if and how calcification protects coccolithophores from microzooplankton predation could not be fully clarified.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Calcium Carbonate Shell of Coccolithophores on Ingestion and Growth of a Dinoflagellate Predator

et al. 2021

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Coccolithophores are an important group of ∼200 marine phytoplankton species which cover themselves with a calcium carbonate shell called “coccosphere.” Coccolithophores are ecologically and biogeochemically important but the reason why they calcify remains elusive. One key function may be that the coccosphere offers protection against microzooplankton predation, which is one of the main causes of phytoplankton death in the ocean. Here, we investigated the effect of the coccosphere on ingestion and growth of the heterotrophic dinoflagellate Oxyrrhis marina. Calcified and decalcified cells of the coccolithophore species Emiliania huxleyi, Pleurochrysis carterae, and Gephyrocapsa oceanica were offered separately to the predator as well as in an initial ∼1:1 mixture. The decrease of the prey concentrations and predator abundances were monitored over a period of 48–72 h. We found that O. marina did not actively select against calcified cells, but rather showed a size selective feeding behavior. Thus, the coccosphere does not provide a direct protection against grazing by O. marina. However, O. marina showed slower growth when calcified coccolithophores were fed. This could be due to reduced digestion rates of calcified cells and/or increased swimming efforts when ballasted with heavy calcium carbonate. Furthermore, we show that the coccosphere reduces the ingestion capacity simply by occupying much of the intracellular space of the predator. We speculate that the slower growth of the grazer when feeding on calcified cells is of limited benefit to the coccolithophore population because other co-occurring phytoplankton species within the community that do not invest energy in the formation of a calcite shell could also benefit from the reduced growth of the predators. Altogether, these new insights constitute a step forward in our understanding of the ecological relevance of calcification in coccolithophores.

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“…This raises the question whether the higher release of viral particles was due to an increased infection of the decalcified cells, or whether the treatment itself affected the replication of the virus. Strom et al (2018) showed that the treatment of E. huxleyi with acid and base caused an elevated release of hydrogen peroxide (H 2 O 2 ) of E. huxleyi into the surrounding medium. An enhanced excretion of H 2 O 2 was also found during the lytic phase of infected E. huxleyi, concomitant with elevated intracellular concentrations of other reactive oxygen species (Evans et al, 2006).…”

Section: Impacts Of the Coccosphere Removal Procedures On Viral Infectionmentioning

confidence: 99%

The Calcium Carbonate Shell of Emiliania huxleyi Provides Limited Protection Against Viral Infection

2020

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Coccolithophores are an important group of marine phytoplankton which cover themselves with the coccosphere -a shell composed of numerous calcium carbonate (CaCO 3 ) platelets. Despite more than a century of coccolithophore research, it remains speculative why coccolithophores calcify. Resolving this question is essential to assess the competitive fitness of coccolithophores in the future ocean where changes in calcification are expected. Here, we used the Emiliania huxleyi -Emiliania huxleyi Virus 86 host-virus model system to test the hypothesis that the coccosphere serves as a physical barrier reducing viral infection. Therefore, we removed the coccosphere from living E. huxleyi cells and compared the infection progress relative to calcified cells in a series of 6 experiments under different growth conditions. We found that the coccosphere does not constitute an effective physical barrier against viral penetration, since non-growing calcified cells were susceptible to viral infection and lysis (growth stopped by light limitation). However, we also found that protection against the virus may depend on the daily growth cycle. E. huxleyi reached higher peak abundances when decalcified cells were allowed to rebuild their coccosphere before entering cell division phase and being exposed to the virus, thereby suggesting that rates of viral infection could be reduced by the coccosphere during the critical phase in the cell cycle. However, the benefit of this potential protection is arguably of limited ecological significance since the concentrations of both, calcified and decalcified E. huxleyi approached similar values until the end of the bloom. We conclude that the coccosphere provides at best a limited protection against infection with the EhV86.

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Phytoplankton defenses: Do Emiliania huxleyi coccoliths protect against microzooplankton predators?

Cited by 7 publications

References 67 publications

The Possession of Coccoliths Fails to Deter Microzooplankton Grazers

The Possession of Coccoliths Fails to Deter Microzooplankton Grazers

Influence of the Calcium Carbonate Shell of Coccolithophores on Ingestion and Growth of a Dinoflagellate Predator

The Calcium Carbonate Shell of Emiliania huxleyi Provides Limited Protection Against Viral Infection

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