Florence Le Gall

Station Biologique de Roscoff · Adaptation et Diversité en Milieu Marin - UMR 7144 CNRS UPMC

Coccolithophores have global ecological and biogeochemical significance as the most important calcifying marine phytoplankton group. The structure and selection of prokaryotic communities associated with the most abundant coccolithophore and bloom‐forming species, Emiliania huxleyi, are still poorly known. In this study, we assessed the diversity o...

The Green Edge project was designed to investigate the onset, life, and fate of a phytoplankton spring bloom (PSB) in the Arctic Ocean. The lengthening of the ice-free period and the warming of seawater, amongst other factors, have induced major changes in Arctic Ocean biology over the last decades. Because the PSB is at the base of the Arctic Ocea...

Diatoms are among the most successful marine eukaryotic phytoplankton groups. Their diversity has been investigated in the world's oceans through expeditions and observations carried out from the equator to the poles. Traditionally, diatom species have been distinguished based on morphological characters of their frustules, but high-throughput sequ...

Marine Synechococcus cyanobacteria are ubiquitous in the ocean, a feature likely related to their extensive genetic diversity. Amongst the major lineages, clades I and IV preferentially thrive in temperate and cold, nutrient-rich waters, whilst clades II and III prefer warm, nitrogen or phosphorus-depleted waters. The existence of such cold (I/IV)...

Major seasonal community reorganizations and associated biomass variations are landmarks of plankton ecology. However, the processes of plankton community turnover rates have not been fully elucidated so far. Here, we analyse patterns of planktonic protist community succession in temperate latitudes, based on quantitative taxonomic data from both m...

Marine Synechococcus cyanobacteria are ubiquitous in the ocean, a feature likely related to their extensive genetic diversity. Amongst the major lineages, clades I and IV preferentially thrive in temperate and cold, nutrient-rich waters, whilst clades II and III prefer warm, nitrogen or phosphorus-depleted waters. The existence of such cold (I/IV)...

Coccolithophores have global ecological and biogeochemical significance as the most important calcifying marine phytoplankton group. The structure and selection of prokaryotic communities associated with the most abundant coccolithophore and bloom-forming species, Emiliania huxleyi, are still poorly known. In this study, we assessed the diversity o...

The Green Edge project was designed to investigate the onset, life and fate of a phytoplankton spring bloom (PSB) in the Arctic Ocean. The lengthening of the ice-free period and the warming of seawater, amongst other factors, have induced major changes in arctic ocean biology over the last decades. Because the PSB is at the base of the Arctic Ocean...

Coccolithophores have global ecological and biogeochemical significance as the most important calcifying marine phytoplankton group. The structure and selection of prokaryotic communities associated with the most abundant coccolithophore and bloom-forming species, Emiliania huxleyi, are still poorly known. In this study, we assessed the diversity o...

Major seasonal community reorganizations and associated biomass variations are landmarks of plankton ecology. However, the processes determining marine species and community turnover rates have not been fully elucidated so far. Here, we analyse patterns of planktonic protist community succession in temperate latitudes, based on quantitative taxonom...

In the Arctic Ocean, the small green alga Micromonas polaris dominates picophytoplankton during the summer months but is also present in winter. It has been previously hypothesized to be phago‐mixotrophic (capable of bacteria ingestion) based on laboratory and field experiments. Prey uptake was analyzed in several M. polaris strains isolated from d...

Annual species succession are important features of marine plankton communities. However, describing the exact sequence of species replacement, and hence understanding the processes at the origin of the recurrent patterns is challenging for microbial species. This study aims at analysing the seasonal and interannual variability of the marine phytop...

In the Arctic Ocean, the small green alga Micromonas polaris dominates pico-phytoplankton during the summer months. It has been previously hypothesized to be phago-mixotrophic (capable of bacteria ingestion) based on laboratory and field experiments. Prey uptake was analysed in several M. polaris strains isolated from different regions and depths o...

In the ocean, Bacillariophyta are one of the most successful protistan groups. Due to their considerable biogeochemical implications, diatom diversity, development, and seasonality have been at the center of research, specifically large-sized species. In comparison, nanoplanktonic diatoms are mostly disregarded from routine monitoring and are often...

Massive phytoplankton blooms develop at the Arctic ice edge, sometimes extending far under the pack ice. An extensive culturing effort was conducted before and during a phytoplankton bloom in Baffin Bay between April and July 2016. Different isolation strategies were applied, including flow cytometry cell sorting, manual single cell pipetting, and...

The Green Edge initiative was developed to investigate the processes controlling the primary productivity and fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Qikiq...

The Green Edge initiative was developed to investigate the processes controlling the primary productivity and the fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Q...

Massive phytoplankton blooms develop at the Arctic ice edge, sometimes extending far under the pack ice. An extensive culturing effort was conducted before and during a phytoplankton bloom in Baffin Bay between April and July 2016. Different isolation strategies were applied, including flow cytometry cell sorting, manual single cell pipetting and s...

The marine diatom Guinardia delicatula is a cosmopolitan species that dominates seasonal blooms in the English Channel and the North Sea. Several eukaryotic parasites are known to induce the mortality of this species. Here, we report the isolation and characterization of the first viruses that infect G. delicatula. Viruses were isolated from the We...

The green picoalgal genus Micromonas is broadly distributed in estuaries, coastal marine habitats and open oceans, from the equator to the poles. Phylogenetic, ecological and genomic analyses of culture strains and natural populations have suggested that this cosmopolitan genus is composed of several cryptic species corresponding to genetic lineage...

Polar environments are undergoing dramatic changes, as the rapidly shrinking ice cover in the Arctic Ocean opens path for phytoplankton blooms profiting from the increased incident light. Green Edge is a multidisciplinary franco-canadien project, enrolling almost 20 institutions from both countries. Its main goal is to understand the dynamics of th...

Flow cytometry provides a tool to physically sort single algal cells in order to obtain clonal cultures. During sorting, cells are submitted to physical stress factors such as high fluidic pressure, exposure to the laser beam, electrostatic charges, deflection through high voltage fields and collisions with container surfaces. All of these can dama...

Photosynthetic eukaryotes have a critical role as the main producers in most ecosystems of the biosphere. The ongoing environmental metabarcoding revolution opens the perspective for holistic eco-systems biological studies of these organisms, in particular the unicellular microalgae that often lack distinctive morphological characters and have comp...

Despite significant research dedicated to the marine genus Phaeocystis, which forms large blooms in the coastal waters of the Southern North Sea, some aspects of the taxonomy and biology of this species still suffer from a sketchy knowledge. It is currently admitted that P. globosa is the species that blooms in the Southern North Sea. This has howe...

Background: DNA barcoding offers an efficient way to determine species identification and to measure biodiversity. For dinoflagellates, an ancient alveolate group of about 2000 described extant species, DNA barcoding studies have revealed large amounts of unrecognized species diversity, most of which is not represented in culture collections. To d...

Neighbour-joining phylogenetic analysis of Alexandrium ITS DNA barcode groups from culture collections in this study and from GenBank as per Fig. 3, with tree labels. Barcode groups are represented by vertical lines. (TIF)

Neighbour-joining phylogenetic analysis of Symbiodinium ITS DNA barcode groups from culture collections in this study and from GenBank as per Fig. 3, with tree labels. Barcode groups are represented by vertical lines. (TIF)

Aerobic anoxygenic phototrophic (AAP) bacteria play significant roles in the bacterioplankton productivity and biogeochemical cycles of the surface ocean. In this study, we applied both cultivation and mRNA-based molecular methods to explore the diversity of AAP bacteria along an oligotrophic gradient in the Mediterranean Sea in early summer 2008....

Aerobic anoxygenic phototrophic (AAP) bacteria play significant roles in the bacterioplankton productivity and biogeochemical cycles of the surface ocean. In this study, we applied both cultivation and mRNA-based molecular methods to explore the diversity of AAP bacteria along an oligotrophic gradient in the Mediterranean Sea in early summer 2008....

During the BIOSOPE cruise in the South-East Pacific Ocean in 2004, several unidentified strains of prasinophytes were isolated into culture. Of these, nine strains composed a group for which the partial 18S rRNA gene sequence was related to Prasinoderma coloniale. The ultrastructure, morphology, division process, pigment composition, genome size an...

In vast areas of the oceans, most of the primary production is performed by cells smaller than 2-3 mum in diameter (picophytoplankton). In recent years, several in situ molecular studies showed a broad genetic diversity of small eukaryotes by sequencing 18S rRNA genes. Compared with photosynthetic cyanobacteria that are dominated by two genera, Pro...

A new chlorarachniophyte, Partenskyella glossopodia gen. et sp. nov., is described from a culture isolated from the Mediterranean Sea pelagic waters and maintained as strain RCC365 at the Roscoff Culture Collection (France). Vegetative cells of P. glossopodia are non-motile naked spherical cells. However, flagellate and amoeboid stages are also pre...

In late 2004, the BIOSOPE cruise sailed between the equatorial influenced waters off the Marquesas Islands and the nutrient enriched waters of the Chilean upwelling. Along the way, it explored the Southeast Pacific gyre centred around Easter Island, which is probably the most oligotrophic oceanic region on earth. During this cruise, we undertook a...

In late 2004, the BIOSOPE cruise sailed between the equatorial influenced waters off the Marquesas Islands and the nutrient enriched waters of the Chilean upwelling. Along the way, it explored the Southeast Pacific gyre centred around Easter Island, which is probably the most oligotrophic oceanic region on earth. During this cruise, we undertook a...

We developed oligonucleotide probes, based on plastid 16S ribosomal DNA (rDNA) sequences, to target 10 different algal classes (Chlorarachniophyceae, Chrysophyceae, Cryptophyceae, Eustigmatophyceae, Pavlovo- phyceae, Pelagophyceae, Pinguiophyceae, Prasinophyceae (clade VI), Prymnesiophyceae, and Trebouxiophyceae), for use with dot blot hybridizatio...

Recent molecular investigations of marine samples taken from different environments, including tropical, temperate and polar areas, as well as deep thermal vents, have revealed an unexpectedly high diversity of protists, some of them forming deep-branching clades within important lineages, such as the alveolates and heterokonts. Using the same appr...

Marine photosynthetic picoeukaryotes (PPEs), representing organisms <3 μm in size, are major contributors to global carbon cycling. However, the key members of the PPE community and hence the major routes of carbon fixation, particularly in the open ocean environment, are poorly described. Here, we have accessed PPE community structure using the pl...

Marine photosynthetic picoeukaryotes (PPEs), representing organisms <3 μm in size, are major contributors to global carbon cycling. However, the key members of the PPE community and hence the major routes of carbon fixation, particularly in the open ocean environment, are poorly described. Here, we have accessed PPE community structure using the pl...

The importance of the cyanobacteria Prochlorococcus and Synechococcus in marine ecosystems in terms of abundance and primary production can be partially explained by ecotypic differentiation. Despite the dominance of eukaryotes within photosynthetic picoplankton in many areas a similar differentiation has never been evidenced for these organisms. H...

Pigment analysis performed on 30 Prasinophyceae strains revealed two main groups: the prasinoxanthin-containing and prasinoxanthin-less Prasinophyceae. Prasinoxanthin-containing Prasinophyceae comprised the orders Mamiellales, Pseudoscourfieldiales (Pycnococcaceae), and Prasinococcales. For this group, classification with pigment composition showed...

Florenciella parvula gen. et sp. nov. (Dictyochophyceae, Heterokontophyta), a small flagellate isolated from the English Channel. Phycologia 43: 658-668. Florenciella parvula (Dictyochophyceae) was isolated from the English Channel in December 2000. In general the cells are spherical, measure 3-6 m and have two markedly unequal flagella as well as...

The Roscoff Culture Collection (RCC, http://www. sb-roscoff. fr/Phyto/RCC/index. php) holds over 500 strains of marine cyanobacteria and microalgae with a strong emphasis on picoplankton, i. e. cells with size below 2-3 microns. Most of these strains have been obtained from the Equatorial Pacific, the Tropical Atlantic, the Mediterranean Sea, the R...

Picoplanktonic prasinophytes are well represented in culture collections and marine samples. In order to better characterize this ecologically important group, we compared the phylogenetic diversity of picoplanktonic prasinophyte strains available at the Roscoff Culture Collection (RCC) and that of nuclear SSU rDNA sequences from environmental clon...