Diversity and Phylogeny of Marine Diatoms

Marine diatoms represent one of the most speciose and ecologically pivotal lineages of phytoplankton, characterised by intricately sculpted silica cell walls and vast morphological diversity. Their taxonomy spans dozens of families and hundreds of genera, with species adapted to environments from the sunlit surface to deep sediments. Advances in molecular phylogenetics have transformed our understanding of their evolutionary history, revealing rapid radiations, cryptic speciation and ancient lineages dating back over 200 million years. Genomic and transcriptomic approaches now underpin robust phylogenetic frameworks, elucidating relationships among key clades such as Thalassiosirales, Chaetocerotales and Bacillariales. Biogeographic surveys have uncovered distinct community assemblages shaped by temperature, nutrient regimes and ocean currents, including hotspots in polar regions and coastal upwelling zones. Many diatom species exhibit remarkable ecological plasticity, modulating their light-harvesting and nitrogen-assimilation machinery in response to changing conditions. Ongoing efforts to integrate high-throughput sequencing, single-cell genomics and experimental physiology have highlighted the dual roles of niche adaptation and historical contingency in driving global patterns of diversity. Understanding diatom phylogeny is not only essential for reconstructing the history of eukaryotic life but also for forecasting the resilience of oceanic carbon and silicon cycles under future climatic perturbations.

Research from Nature Portfolio

Recent studies have leveraged combined molecular and morphological data from global expeditions to map diatom diversity and abundance across ocean basins. One large-scale analysis defined 25 distinct diatom communities, pinpointing the Arctic as a biodiversity hotspot and identifying dominant genera such as Chaetoceros and Thalassiosira. This work further explored transcriptional investment in light harvesting and photoprotection, offering insights into adaptive strategies under variable irradiance and nutrient regimes. Another foundational project applied high-throughput metabarcoding of 18S rRNA and rDNA across multiple European coastal sites, revealing near-complete assignment of reads to known genera and species and uncovering a tight bentho-pelagic coupling whereby many taxa colonise both water column and sediments. This study confirmed that combining rRNA and rDNA data enhances detection of rare taxa, particularly within sediment communities, and underscored the potential of metabarcoding to resolve fine-scale ecological patterns.

Diversity and Phylogeny of Marine Diatoms publication trend

The graph below shows the total number of articles in diversity and phylogeny of marine diatoms across all publications each year (not limited to Nature Index journals).

Technical terms

Metabarcoding: High-throughput sequencing technique that identifies organisms by amplifying and sequencing marker genes from mixed environmental samples.

Phylogenetic haplotype network: A graphical representation of evolutionary relationships among closely related sequences, illustrating mutational steps and potential gene flow.

Cryptic species: Distinct evolutionary lineages that are morphologically similar but genetically divergent, often discovered through molecular methods.

Bentho-pelagic coupling: Ecological linkage between benthic (seafloor) and pelagic (water column) habitats, where species colonise and interact across both zones.

Frustule: Silica-based cell wall of diatoms, composed of two interlocking valves, often ornamented with species-specific patterns.

References

1. Patterns and drivers of diatom diversity and abundance in the global ocean. Nature Communications (2025).
2. Diatom diversity through HTS-metabarcoding in coastal European seas. Scientific Reports (2018).
3. Differential ecological adaptation of diverse Chaetoceros species revealed by metabarcoding analysis. Environmental DNA (2023).
4. Resolving cryptic species complexes in marine protists: phylogenetic haplotype networks meet global DNA metabarcoding datasets. The ISME Journal: Multidisciplinary Journal of Microbial Ecology (2021).
5. Diversity and biogeography of planktonic diatoms in Svalbard fjords: The role of dispersal and Arctic endemism in phytoplankton community structuring. Elementa: Science of the Anthropocene (2022).