What question did this study set out to answer?

This research aims to understand the diversity and ecological roles of ultra-small prokaryotes that escape standard filtration methods.

June 17, 2026Open Access

View Full Paper

The Elusive Fraction of Marine Plankton Diversity: Size, Abundance and Taxonomic Composition of 0.2 μm‐Filterable Prokaryotes Across Three Contrasting Coastal Environments

CRClara Ruiz‐GonzálezInstitut Català de Ciències del Clima CACristina Andrés‐BarraoKing Abdullah University of Science and Technology ALAnders LanzénIkerbasque

Key Points

This research aims to understand the diversity and ecological roles of ultra-small prokaryotes that escape standard filtration methods.
Characterized prokaryotic assemblages from 0.1-0.22 μm and >0.22 μm size fractions.
Conducted analyses across sites in the NE Atlantic, NW Mediterranean Sea, and the Red Sea.
Examined the influence of organic carbon concentration and temperature on prokaryotic composition.
9%-15% of total prokaryotic cells passed through 0.22-μm filters, with mean sizes 16%-46% smaller than unfiltered communities.
FP communities exhibited lower taxonomic richness compared to 0.2RP fractions, with specific groups enriched in FP assemblages.
Taxonomic dissimilarity between FP and 0.2RP increased with higher organic carbon concentration, indicating a response to nutrient availability.

Abstract

The existence of prokaryotes escaping filtration through 0.2-μm filters has been known for decades. Such 'filterable' prokaryotes (hereafter 'FP') might include true ultra-small groups (i.e., ultramicrobacteria), but also cells that miniaturize temporally as a physiological strategy to persist under unfavourable conditions, representing a 'seed bank' that can flourish when conditions change. However, the taxonomy, environmental drivers and ecological relevance of these microorganisms remain unknown due to a scarcity of studies targeting this size-fraction. We characterized prokaryotic assemblages from the 0.1-0.22 μm and the > 0.22-μm ('0.2RP' for 0.22-μm-retained prokaryotes) size-fractions across different sites in the NE Atlantic (Bay of Biscay), the NW Mediterranean Sea and the Red Sea. 9%-15% of total cells passed through 0.22-μm filters and their mean cell size was 16%-46% smaller than that of the unfiltered community. FP consistently showed lower taxonomic richness than the 0.2RP fraction. Known small-sized groups like Pelagibacterales, Actinobacteriota and Thermoplasmatota were significantly enriched in FP assemblages, but typical normal-sized bacteria such as Flavobacteriales were also detected, suggesting the presence of miniaturized cells of widespread marine prokaryotes. Distinct environmental drivers shaped different FP subpopulations, as the contribution of specific taxa within the FP communities varied with organic carbon (OC) concentration and temperature. Notably, taxonomic dissimilarity between both fractions increased with higher OC concentration, suggesting that more normal-sized taxa may be miniaturized towards conditions of less OC availability. Overall, our results suggest that the widespread use of 0.2-μm filters likely results in significant losses of the extant diversity, potentially hiding ecologically important roles in marine ecosystems.

Demander à l'IA

Bookmark

View Full Paper

Demander à l'IA

Bookmark

View Full Paper

The Elusive Fraction of Marine Plankton Diversity: Size, Abundance and Taxonomic Composition of 0.2 μm‐Filterable Prokaryotes Across Three Contrasting Coastal Environments

Key Points

Abstract

Cite This Study

Also Consider

Also Consider