Parasitism Dynamics in Marine Protist Communities

Parasitism among marine protists represents a fundamental but often overlooked driver of oceanic food-web structure, biogeochemical cycling and ecosystem resilience. Protist parasites, notably within the Alveolata, infect a broad range of hosts from phytoplankton to metazoans, resulting in host mortality, nutrient release and shifts in community composition. These interactions influence primary production, carbon export and the fate of harmful algal blooms. Advances in single-cell ‘omics and environmental sequencing have uncovered previously cryptic lineages and revealed that parasitism has arisen multiple times among early-branching dinoflagellates, often accompanied by repeated loss or modification of plastid organelles. Network-based approaches and long-term time-series studies have begun to resolve depth-dependent host-parasite associations, temporal peaks of infection and ecological niches of parasite life stages. Together, these findings underscore the global significance of protist parasitism in modulating plankton succession, attenuating carbon flux and shaping microbial community networks. Understanding these dynamics is critical for improving predictive models of marine food webs and for developing bioindicators of ecosystem health under changing ocean conditions.

Research from Nature Portfolio

Recent analyses of single-cell transcriptomes have demonstrated that parasitic marine alveolates evolved independently on multiple occasions from free-living relatives, paralleling patterns seen in apicomplexan parasites. This work elucidated distinct ancestral lineages among Syndiniales and Ichthyodinida, and revealed repeated loss of photosynthetic pathways alongside retention of non-photosynthetic plastid functions. Complementary meta-analysis of global environmental surveys has uncovered a vast and previously unrecognised diversity of Perkinsea across marine and terrestrial habitats. Hundreds of novel genetic clusters were detected, extending the known distribution of these parasites from coastal waters to abyssal sediments and highlighting their likely ecological roles beyond classic host systems.

Parasitism Dynamics in Marine Protist Communities publication trend

The graph below shows the total number of articles in parasitism dynamics in marine protist communities across all publications each year (not limited to Nature Index journals).

Technical terms

Protist: A diverse group of mostly unicellular eukaryotes, including algae, protozoa and fungus-like organisms.

Parasitism: A symbiotic interaction in which one organism (the parasite) lives on or within a host and derives nutrients at the host’s expense.

Marine Alveolates: A clade of protists (including Dinoflagellata, Apicomplexa and related lineages) characterised by cortical sacs (‘alveoli’) beneath the cell membrane.

Syndiniales: An order of parasitic marine alveolates that infect a wide range of hosts, often dominating marine parasitic networks.

Plastid: A membrane-bound organelle involved in photosynthesis or other metabolic functions, variably retained or lost in parasitic lineages.

Metabarcoding: A high-throughput DNA sequencing technique targeting taxonomic marker genes to assess community composition.

Co-occurrence network: A graph-based representation of statistical associations among taxa, inferred from environmental sequencing data to predict ecological interactions.

References

1. Multiple parallel origins of parasitic Marine Alveolates. Nature Communications (2023).
2. Role of Syndiniales parasites in depth-specific networks and carbon flux in the oligotrophic ocean. ISME Communications (2024).
3. Global perspective of environmental distribution and diversity of Perkinsea (Alveolata) explored by a meta-analysis of eDNA surveys. Scientific Reports (2023).
4. Temporal Variability and Ecological Interactions of Parasitic Marine Syndiniales in Coastal Protist Communities. mSphere (2020).