TY - JOUR T1 - Beyond the limits of the unassigned protist microbiome: inferring large-scale spatio-temporal patterns of Syndiniales marine parasites A1 - Rizos,Iris A1 - Debeljak,Pavla A1 - Finet,Thomas A1 - Klein,Dylan A1 - Ayata,Sakina-Dorothée A1 - Not,Fabrice A1 - Bittner,Lucie AD - Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, Paris, France AD - Sorbonne Université, CNRS, AD2M-UMR7144 Station Biologique de Roscoff, 29680, Roscoff, France AD - Sorbonne Université, Laboratoire d’Océanographie et du Climat: Expérimentation et Analyses Numériques (LOCEAN, SU/CNRS/IRD/MNHN), 75252, Paris Cedex 05, France AD - Institut Universitaire de France, Paris, France UR - https://archimer.ifremer.fr/doc/00823/93480/ DO - 10.1038/s43705-022-00203-7 N2 - Marine protists are major components of the oceanic microbiome that remain largely unrepresented in culture collections and genomic reference databases. The exploration of this uncharted protist diversity in oceanic communities relies essentially on studying genetic markers from the environment as taxonomic barcodes. Here we report that across 6 large scale spatio-temporal planktonic surveys, half of the genetic barcodes remain taxonomically unassigned at the genus level, preventing a fine ecological understanding for numerous protist lineages. Among them, parasitic Syndiniales (Dinoflagellata) appear as the least described protist group. We have developed a computational workflow, integrating diverse 18S rDNA gene metabarcoding datasets, in order to infer large-scale ecological patterns at 100% similarity of the genetic marker, overcoming the limitation of taxonomic assignment. From a spatial perspective, we identified 2171 unassigned clusters, i.e., Syndiniales sequences with 100% similarity, exclusively shared between the Tropical/Subtropical Ocean and the Mediterranean Sea among all Syndiniales orders and 25 ubiquitous clusters shared within all the studied marine regions. From a temporal perspective, over 3 time-series, we highlighted 39 unassigned clusters that follow rhythmic patterns of recurrence and are the best indicators of parasite community’s variation. These clusters withhold potential as ecosystem change indicators, mirroring their associated host community responses. Our results underline the importance of Syndiniales in structuring planktonic communities through space and time, raising questions regarding host-parasite association specificity and the trophic mode of persistent Syndiniales, while providing an innovative framework for prioritizing unassigned protist taxa for further description. Y1 - 2023/02 PB - Springer Science and Business Media LLC JF - Isme Communications SN - 2730-6151 VL - 3 IS - 1 ID - 93480 ER -