Picoeukaryotes (< 3 µm) diversity coastal site of the English Channel Khadidja Romari & Daniel Vaulot PICODIV meeting Oslo - March 2003

Roscoff Station: Astan Year 2000 April June September December Year 2001 April May June Year 2001 May Sampling strategy

RFLP Analysis of environmental clone libraries June 2001 Sept.2001 Dourd. May 2001 May 2001 Apri Apri Dec June 2000

Clone library Astan Dourduff Date 12 April June Sept Dec April May June # of RFLP typesCoverage value (%) 17 May * 100 positives clones were screened by RFLP for each clone library * Coverage value (C) = 1- n/N, (n = number of RFLP type; N = number of clone analysed) RFLP-Analysis of environmental clone libraries

Clones  99.5 % sequence simil. OTU OTU with similarity  98 % Phylotype OTU OTU : Operational taxonomic unit Phylotype : Genus/species level OTU: Ecotype level

Groups # phylotypes # OTUs Prasinophyceae 9 28 Cryptophyceae 6 22 Prymnesiophyceae 3 6 Dinophyceae 7 11 Cercozoa Choanoflagellates 5 6 Stramenopiles Alveolate group I 4 7 Alveolate group II Ciliates Rosko II 6 12 Rosko I (Telonema ) 4 8 Total Diversity inside the groups OTUs : Clones with similarity  98% and < 99,5 % Phylotypes : OTUs with similarity < 98 %

Phylotype level: Heterotrophs are more diverse than phototrophs Groups# Phylotypes Heterotrophs 108 Phototrophs 21 # OTUs Diversity : Phototrophs vs heterotrophs OTU level: Phototrophs are relatively more diverse than heterotrophs

Photosynthetic groups Prasinophyceae Micromonas, Bathycoccus, Ostreococcus also Pyramimonas, CCMP 1205 Cryptophyceae (nucleus and nucleomorph) Geminigera Prymnesiophyceae uncultivated group, Chrysochromulina Dinophyceae Gymnodinium, Prorocentrum, Dinophysis Ostreococcus

Non photosynthetic groups Stramenopiles all clades defined by Ramon plus a new one Cafeteria Uncultivated alveolates mostly group II (Amoebophrya) Ciliates no strong identity with known species Cercozoa Cryothecomonas, Cercomonas Picture from S. Kuhn Cryothecomonas Choanoflagellates no strong identity with known species Telonema

Temporal and spatial variability

Astan Station Sporadic phylotypes (appearing only once)

Conclusions High diversity (not fully covered by clone sampling) Confirm ubiquity of novel alveolates and stramenopiles Specificity of coastal areas (temperate ?) Mamiellales Cryptophyceae Ciliates Cercozoa Two novel groups ? Diatom bloom library has unique features low diversity mostly sporadic phylotypes Estuarine library very different from Astan library dominated by Ciliates some groups absent (Cryptophyceae)

Acknowledgements PICODIV CNRS-Aventis Foundation BIOSOPE (funded by CNRS) PICOMANCHE (Brittany region program) The Mysis crew Fabrice Not (Collecting samples)