Picoeukaryotes (< 3 µm) diversity

coastal site of the English Channel

Khadidja Romari & Daniel Vaulot

PICODIV meeting

Oslo - March 2003

Roscoff

Station: Astan Year 2000April June

SeptemberDecember

Year 2001AprilMayJune

Year 2001May

Sampling strategy

RFLP Analysis of environmental clone libraries

Rarefaction curves

0

10

20

30

40

50

60

70

0 20 40 60 80 100

Number of clones

Cum

ulat

ive

RFLP

- t

ype

Num

ber

June 2001

Sept.2001

Dourd. May 2001May 2001

Apri. 2000

Apri. 2001

Dec. 2000

June 2000

Clone library

Astan

Dourduff

Date

12 April 2000 65 35

9 June 2000 54 46

7 Sept 2000 68 32

19 Dec 2000 60 40

12 April 2001 54 46

16 May 2001 65 35

13 June 2001 41 59

# of RFLP types Coverage value (%)

17 May 2001 52 48

* 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

OTU with similarity 98 %

Phylotype

OTU

OTU : Operational taxonomic unit

Phylotype : Genus/species levelOTU: Ecotype level

Groups # phylotypes # OTUs

Prasinophyceae 9 28 Cryptophyceae 6 22 Prymnesiophyceae 3 6 Dinophyceae 7 11 Cercozoa 19 25 Choanoflagellates 5 6 Stramenopiles 26 40 Alveolate group I 4 7 Alveolate group II 25 42 Ciliates 23 38 Rosko II 6 12 Rosko I (Telonema ) 4 8

Total 137 245

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

164

83

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

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

april 00 june 00 sept 00 dec 00 april 01 may 01 june 01 may 01(Dourduff)

# O

TU

s

Prasinophyceae Cryptophyceae Prymnesiophyceae Dinophyceae Choanoflagellates

Stramenopiles Cercozoa Alveolate group II Alveolate group I Perkinsozoa

Ciliates Rosko I (Telonema) Rosko II

Temporal and spatial variability

Astan StationSporadic phylotypes (appearing only

once)observed

Apr-00 Jun-00 Sep-00 Dec-00 Apr-01 May-01 Jun-01 Total % of all phylotypes

Prasinophyceae 8 1 1 2 25%

Cryptophyta (includes nucleomorph) 6 1 1 17%

Haptophyta 3 1 1 2 67%

Cercozoa 18 2 3 7 2 2 16 89%

Choanoflagellates 4 1 2 3 75%

Stramenopiles 26 5 3 2 1 1 5 17 65%

Perkinsozoa 1 1 1

Dinophyceae 7 4 1 5 71%

Alveolate group I 4 1 1 2 50%

Alveolate group II 25 4 1 3 4 2 6 20 80%

Ciliates 14 1 2 2 1 6 43%

Rosko I 6 2 2 4 67%

Rosko II 4 1 1 1 3 75%

Fungi 1 1 1

RA000609.30 1 1 1

Total number of phylotypes observed only once 14 14 9 11 12 6 18 84 66%

Total number of phylotypes 128 44 31 28 26 29 27 30

% of phylotypes observed once 32% 45% 32% 42% 41% 22% 60%

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)