Algal blooms

Schleyer, Guy; Vardi, Assaf

doi:10.1016/j.cub.2020.07.011

Cited by 21 publications

(14 citation statements)

References 11 publications

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“…Marine algae are responsible for half of Earth’s primary production and form the basis of the oceanic food chain 1 . Algal blooms 2 are ephemeral events of phytoplankton proliferation that occur annually across the globe 3 covering thousands of square kilometers. Upon bloom demise, most of the fixed carbon is transferred to higher trophic levels either via herbivorous predation or through heterotrophic bacteria and their predators (a process called the “microbial loop”), being largely recycled and respired along the way 4 , 5 .…”

Section: Introductionmentioning

confidence: 99%

Viral infection switches the balance between bacterial and eukaryotic recyclers of organic matter during coccolithophore blooms

et al. 2023

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Algal blooms are hotspots of marine primary production and play central roles in microbial ecology and global elemental cycling. Upon demise of the bloom, organic carbon is partly respired and partly transferred to either higher trophic levels, bacterial biomass production or sinking. Viral infection can lead to bloom termination, but its impact on the fate of carbon remains largely unquantified. Here, we characterize the interplay between viral infection and the composition of a bloom-associated microbiome and consequently the evolving biogeochemical landscape, by conducting a large-scale mesocosm experiment where we monitor seven induced coccolithophore blooms. The blooms show different degrees of viral infection and reveal that only high levels of viral infection are followed by significant shifts in the composition of free-living bacterial and eukaryotic assemblages. Intriguingly, upon viral infection the biomass of eukaryotic heterotrophs (thraustochytrids) rivals that of bacteria as potential recyclers of organic matter. By combining modeling and quantification of active viral infection at a single-cell resolution, we estimate that viral infection causes a 2–4 fold increase in per-cell rates of extracellular carbon release in the form of acidic polysaccharides and particulate inorganic carbon, two major contributors to carbon sinking into the deep ocean. These results reveal the impact of viral infection on the fate of carbon through microbial recyclers of organic matter in large-scale coccolithophore blooms.

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Section: Introductionmentioning

confidence: 99%

Viral infection switches the balance between bacterial and eukaryotic recyclers of organic matter during coccolithophore blooms

et al. 2023

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“…Algal blooms are ephemeral events of massive cell proliferation, serving as ecological hotspots of primary production and microbial interactions in the ocean (1). Marine viruses are a major factor controlling algal blooms.…”

Section: Introductionmentioning

confidence: 99%

Cell-to-cell heterogeneity drives host-virus coexistence in a bloom-forming alga

Joffe,

Kuhlisch,

Schleyer

et al. 2023

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Algal blooms drive global biogeochemical cycles of key nutrients in the oceans and serve as hotspots for biological interactions. The massive spring blooms of the cosmopolitan coccolithophoreEmiliania huxleyi (E. huxleyi)are often infected by the lyticEmiliania huxleyispecific virus (EhV) which is a major mortality agent triggering bloom demise. Nonetheless, the multi-annual “boom and bust” pattern ofE. huxleyisuggests that mechanisms of coexistence are essential for these host-virus dynamics. To investigate host-virus coexistence, we developed a new model system from anE. huxleyiculture which recovered from viral infection. The recovered population coexists with the virus, as host cells continue to grow in parallel to viral production. By applying a single-molecule fluorescencein situhybridization (smFISH) approach to quantify the fraction of infected cells and assessing infection-specific lipid biomarkers, we identified a small subpopulation (5-7% of cells) that was infected and produced new virions, whereas the majority of the host population could resist infection. To further assess population heterogeneity, we generated monoclonal strain collections using single-cell sorting and subsequently phenotyped their susceptibility to EhV infection. This unraveled a substantial cell-to-cell heterogeneity across a continuum of susceptibility to resistance, suggesting that infection outcomes may vary depending on the individual cell. These results add a new dimension to our understanding of the complexity of host-virus interactions that are commonly assessed in bulk and described by binary definitions of resistance or susceptibility. We propose that phenotypic heterogeneity drivesE. huxleyi-EhV coexistence and may potentially provide the coexisting strain an ecological advantage by killing competing susceptible strains.

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“…Algal blooms occur across oceans and lakes annually, covering up to thousands of square kilometers 1 . These hotspots of primary production impact global biogeochemical cycles 2,3 , release volatiles that contribute to cloud formation 4 , and influence marine microbial food webs 5 .…”

Section: Introductionmentioning

confidence: 99%

Daily turnover of active giant virus infection during algal blooms revealed by single-cell transcriptomics

Hevroni¹,

Vincent²,

Ku³

et al. 2022

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Viruses are the most abundant biological entity in the ocean and play a significant role in shaping the marine ecosystem. The past two decades have revealed an outstanding diversity of giant viruses infecting protists across the tree of life and, in particular, algae that form massive blooms in the ocean. Virus-induced bloom demise significantly impacts marine ecology and biogeochemistry, as well as the associated microbial community. Nevertheless, little is known about the infection dynamics of these giant viruses in the natural environment and their role in regulating algal blooms. Here, we provide evidence for a daily life cycle of giant viral infection in algal blooms by processing the transcriptome of over 12,000 single algal cells during different phases of interaction with their giant viruses. We revealed that viral infection occurs already at the exponential phase of the bloom and that the timing of infection can determine the magnitude of the bloom but not the fraction of infected cells. We further revealed that the same proportion of infected cells are in the early phase of the viral replication program (13.5%) throughout several consecutive days of the bloom, suggesting that a daily turnover of infection is at play during the bloom and demise phases of the algal population. This may imply that a continuous source of virocell-associated metabolites diffuses throughout the bloom succession and could fuel the microbial food webs. Finally, we link single cell infection state to host physiology and show that infected cells remained calcified even in the late stage of infection, contradicting common observation of bulk population in which viral infection is directly linked with decalcification. Together, these results highlight the importance of studying host-virus dynamics in natural populations at a single-cell resolution, which can provide a fresh view of the dynamics and propagation of viral infection. This approach will enable quantification of the impact of marine viruses on microbial food webs.

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Algal blooms

Cited by 21 publications

References 11 publications

Viral infection switches the balance between bacterial and eukaryotic recyclers of organic matter during coccolithophore blooms

Viral infection switches the balance between bacterial and eukaryotic recyclers of organic matter during coccolithophore blooms

Cell-to-cell heterogeneity drives host-virus coexistence in a bloom-forming alga

Daily turnover of active giant virus infection during algal blooms revealed by single-cell transcriptomics

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