Widespread distribution of a unique marine protistan lineage

摘要: Unicellular eukaryotes (protists) are key components of marine food webs, yet knowledge their diversity, distributions and respective ecologies is limited. We investigated uncultured protists using 18S rRNA gene sequencing, phylogenetic analyses, specific fluorescence in situ hybridization (FISH) probes other methods. Because few studies have been conducted warm water systems, we focused on two Atlantic subtropical regions, the Sargasso Sea Florida Current. Cold temperate waters were also sampled. Gene sequences comprising a unique eukaryotic lineage, herein termed ‘biliphytes’, identified most samples, whether from high- (30°C) or low- (5°C) temperature waters. Sequences within this group previously retrieved high latitudes. Phylogenetic analyses suggest biliphytes sister to cryptophytes katablepharids, although relationship not statistically supported. Bootstrap-supported subclades delineated but coherence was obvious with respect geography physicochemical parameters. Unlike results initial publication these organisms (therein ‘picobiliphytes’), could detect nucleomorph, either visually, by targeted primers. Phycobilin-like associated biliphyte-specific FISH-probed cells supports hypothesis that they photosynthetic. Our data indicate nanoplanktonic size, averaging 4.1 ± 1.0 × 3.5 0.8 μm (±SD) for one probed group, 0.9 3.0 another. estimate contributed 28 (±6)% phytoplanktonic biomass tropical eddy-influenced surface Given broad thermal geographic distribution, understanding role play biogeochemical cycling different habitats essential.