@article {31051, title = {Nanoplanktonic diatoms are globally overlooked but play a role in spring blooms and carbon export.}, journal = {Nat Commun}, volume = {9}, year = {2018}, month = {2018 Mar 05}, pages = {953}, abstract = {

Diatoms are one of the major primary producers in the ocean, responsible annually for ~20\% of photosynthetically fixed COon Earth. In oceanic models, they are typically represented as large (\>20 {\textmu}m) microphytoplankton. However, many diatoms belong to the nanophytoplankton (2-20 {\textmu}m) and a few species even overlap with the picoplanktonic size-class (\<2 {\textmu}m). Due to their minute size and difficulty of detection they are poorly characterized. Here we describe a massive spring bloom of the smallest known diatom (Minidiscus) in the northwestern Mediterranean Sea. Analysis of Tara Oceans data, together with literature review, reveal a general oversight of the significance of these small diatoms at the global scale. We further evidence that they can reach the seafloor at high sinking rates, implying the need to revise our classical binary vision of pico- and nanoplanktonic cells fueling the microbial loop, while only microphytoplankton sustain secondary trophic levels and carbon export.

}, issn = {2041-1723}, doi = {10.1038/s41467-018-03376-9}, author = {Leblanc, Karine and Qu{\'e}guiner, Bernard and Diaz, Fr{\'e}d{\'e}ric and Cornet, V{\'e}ronique and Michel-Rodriguez, M{\'o}nica and Durrieu de Madron, Xavier and Bowler, Chris and Malviya, Shruti and Thyssen, Melilotus and Gr{\'e}gori, G{\'e}rald and Rembauville, Mathieu and Grosso, Olivier and Poulain, Julie and de Vargas, Colomban and Pujo-Pay, Mireille and Conan, Pascal} } @article {30155, title = {Neobodonids are dominant kinetoplastids in the global ocean.}, journal = {Environ Microbiol}, volume = {20}, year = {2018}, month = {2018 Feb}, pages = {878-889}, abstract = {

Kinetoplastid flagellates comprise basal mostly free-living bodonids and derived obligatory parasitic trypanosomatids, which belong to the best-studied protists. Due to their omnipresence in aquatic environments and soil, the bodonids are of ecological significance. Here, we present the first global survey of marine kinetoplastids and compare it with the strikingly different patterns of abundance and diversity in their sister clade, the diplonemids. Based on analysis of 18S rDNA V9 ribotypes obtained from 124 sites sampled during the Tara Oceans expedition, our results show generally low to moderate abundance and diversity of planktonic kinetoplastids. Although we have identified all major kinetoplastid lineages, 98\% of kinetoplastid reads are represented by neobodonids, namely specimens of the Neobodo and Rhynchomonas genera, which make up 59\% and 18\% of all reads, respectively. Most kinetoplastids have small cell size (0.8-5 {\textmu}m) and tend to be more abundant in the mesopelagic as compared to the euphotic zone. Some of the most abundant operational taxonomic units have distinct geographical distributions, and three novel putatively parasitic neobodonids were identified, along with their potential hosts.

}, issn = {1462-2920}, doi = {10.1111/1462-2920.14034}, author = {Flegontova, Olga and Flegontov, Pavel and Malviya, Shruti and Poulain, Julie and de Vargas, Colomban and Bowler, Chris and Luke{\v s}, Julius and Hor{\'a}k, Ale{\v s}} } @article {36659, title = {Ubiquitous abundance distribution of non-dominant plankton across the global ocean.}, journal = {Nat Ecol Evol}, year = {2018}, month = {2018 Jun 18}, abstract = {

Marine plankton populate 70\% of Earth{\textquoteright}s surface, providing the energy that fuels ocean food webs and contributing to global biogeochemical cycles. Plankton communities are extremely diverse and geographically variable, and are overwhelmingly composed of low-abundance species. The role of this rare biosphere and its ecological underpinnings are however still unclear. Here, we analyse the extensive dataset generated by the Tara Oceans expedition for marine microbial eukaryotes (protists) and use an adaptive algorithm to explore how metabarcoding-based abundance distributions vary across plankton communities in the global ocean. We show that the decay in abundance of non-dominant operational taxonomic units, which comprise over 99\% of local richness, is commonly governed by a power-law. Despite the high spatial turnover in species composition, the power-law exponent varies by less than 10\% across locations and shows no biogeographical signature, but is weakly modulated by cell size. Such striking regularity suggests that the assembly of plankton communities in the dynamic and highly variable ocean environment is governed by large-scale ubiquitous processes. Understanding their origin and impact on plankton ecology will be important for evaluating the resilience of marine biodiversity in a changing ocean.

}, issn = {2397-334X}, doi = {10.1038/s41559-018-0587-2}, author = {Ser-Giacomi, Enrico and Zinger, Lucie and Malviya, Shruti and de Vargas, Colomban and Karsenti, Eric and Bowler, Chris and De Monte, Silvia} }