1. Woods Hole Oceanographic Insitution
2013 CMORE SUMMER COURSE
Student symposium
1st June 2013, Honolulu, HI
Investigating Trichodesmium ecophysiology and the factors determining niche differentiation in the North Atlantic Ocean
Mónica Rouco
Woods Hole Oceanographic Insitution
Dr. Sonya Dyhrman´s lab
Photo: Abby Heithoff

2. DIAZOTROPHIC CYANOBACTERIA
Tropical and subtropical waters
Photos: A. Heithoff; E. Orchard

3. FACTORS INFLUENCING TRICHODESMIUM N2FIXATION &GROWTH
LIGHT INTENSITY
(Breitbarth et al.
2008. Mar Ecol Prog Ser)
TEMPERATURE
(Breitbarth et al. 2007
Biogeosciences; Hutchins et al. 2008).
MIX LAYER DEPTH/VERTICAL STRATRIFICATION
(Karl et al. (2001); Sañudo-Wilhelmy et al. (2001)).
NUTRIENTS and
TRACE METALS
IRON (Moore et al Nature Geoscience)
PHOSPHORUS (Sañudo-Wilhelmy et al. 2001, Nature; Moore et al. 2004, GBC; Hynes et al. 2009)
Photo: E. Orchard

4. COLONY MORPHOLOGY B A C Raft/tuft Puff Bowtie
Hynes et al. (2012) J. Phycol. 48, 196–210 (2012)

5. TRICHODESMIUM SPECIES
Trichodesmium contortum
Trichodesmium erythraeum
Trichodesmium tenue
Trichodesmium thiebautii
Trichodesmium spiralis
Trichodesmium hildebrandtii
Overlapping Characteristics
Clade I
(erythraeum like)
Clade II
(thebautti like)
Hynes et al. (2012) J. Phycol

6. FACTORS INFLUENCING TRICHODESMIUM N2FIXATION &GROWTH
LIGHT INTENSITY
(Breitbarth et al.
2008. Mar Ecol Prog Ser)
TEMPERATURE
(Breitbarth et al. 2007
Biogeosciences; Hutchins et al. 2008).
MIX LAYER DEPTH/VERTICAL STRATRIFICATION
(Karl et al. (2001); Sañudo-Wilhelmy et al. (2001)).
NUTRIENTS and
TRACE METALS
IRON (Moore et al Nature Geoscience)
PHOSPHORUS (Sañudo-Wilhelmy et al. 2001, Nature; Moore et al. 2004, GBC; Hynes et al. 2009)
INTRINSIC ABILITIES
Photo: E. Orchard

7. MOTIVATION FOR THIS PROJECT
C.S. Davis and D. McGillicuddy (2006) Science 312, 1517
Unexpected vertical Trichodesmium spp. distribution
More uniform than previously thought
Unexpected vertical Trichodesmium spp. distribution
More uniform than previously thought

8. QUESTIONS...
Is the vertical distribution of Trichodesmium spp. in the high abundance region of the western tropical North Atlantic similar to that reported in Davis and McGillicuddy (2006)?
Are the deep populations of Trichodesmium spp. actively fixing nitrogen?
Spatial and vertical clade distribution (qPCR) Niche differentiation.
Physiological ecology of surface v subsurface populations. RNA Seq (Metatranscriptomics).

9. OC471
Spring 2010
Map section: Elise Olson

10. Trichodesmium abundance: VPR
MEASURED PARAMETERS (OC471)
Trichodesmium abundance: VPR
(Elise Olson & Dennis McGillicudy, Cabell Davis)
N2 fixation rates (Acetylene reduction assay):
Surface (5-15m)
Subsurface (below predicted MLD)
Clade distribution: DNA (0,20,40,60,80m) qPCR
High-throughput transcriptome sequencing: RNA

11. TRICHODESMIUM VERTICAL PATTERNS (VPR)
VPR (Elise Olson & Dennis McGillicuddy)
There is a vertical distribution of Trichodesmium populations.
Rafts are associated with the surface and puffs are unevenly distributed.

12. Subsurface populations are actively fixing N2
N2 FIXATION
Average SURFACE N2 FIX : ± 59.6 µmol N h-1 molC-1
Average SUBSURFACE N2 FIX: ± 48.6 µmol N h-1 molC-1
Subsurface populations are actively fixing N2

13. q-PCR based methodology (DNA)
ADAPTIVE ECOTYPES SEGREGATED IN THE WATER COLUMN
q-PCR based methodology (DNA)
6 species
Trichodesmium contortum
Trichodesmium erythraeum
Trichodesmium tenue
Trichodesmium thiebautii
Trichodesmium spiralis
Trichodesmium hildebrandtii
Clade I
Clade II

14. Clade I(erythraeum like)
ADAPTIVE ECOTYPES SEGREGATED IN THE WATER COLUMN
q-PCR based methodology (DNA)
6 species
Trichodesmium contortum
Trichodesmium erythraeum (IMS 101)
Trichodesmium tenue
Trichodesmium thiebautii
Trichodesmium spiralis
Trichodesmium hildebrandtii
Clade I(erythraeum like)
Clade II
(thebautii
like)

15. Clade I (erythraeum like) Clade II (thebautii like)
ADAPTIVE ECOTYPES SEGREGATED IN THE WATER COLUMN
q-PCR based methodology (DNA)
6 species
Trichodesmium contortum
Trichodesmium erythraeum (IMS 101)
Trichodesmium tenue
Trichodesmium thiebautii (VI-I)
Trichodesmium spiralis
Trichodesmium hildebrandtii
Clade I (erythraeum like)
Clade II (thebautii like)

16. Clade specific primers
ADAPTIVE ECOTYPES SEGREGATED IN THE WATER COLUMN
q-PCR
rnpB gene (RNase P)
Clade specific primers
Chappel & Webb (2010) Environmental Microbiology
STANDARD CURVE
FILTERS ,DILUTIONS
Cell concentration
(total filament lengths + average cell length)
DNA extraction
qPCR

17. thebautii like populations
SPECIES SEGREGATION IN THE WATER COLUMN (OC471) 5 8 2 3 4 6 7
9/16 10 15 11
13/14 12 5 8 2 3 4 6 7
9/16 10 15 11
13/14 12
91-100%
thebautii like populations

18. (Salinity, Temperature)
SPECIES SEGREGATION IN THE WATER COLUMN (OC471) 5 8 2 3 4 6 7
9/16 10 15 11
13/14 12 5 8 2 3 4 6 7
9/16 10 15 11
13/14 12
PCA
(Salinity, Temperature)

19. SPECIES SEGREGATION IN THE WATER COLUMN (HOE-DYLAN)
Cryptic bloom of
erythraeum?

20. CONCLUSIONS
There is a vertical distribution of Trichodesmium populations.
Rafts are associated with the surface and puffs are unevenly distributed.
Subsurface populations are actively fixing nitrogen but yield lower rates than those observed by surface populations.
91-100% of the Trichodesmium populations along the OC471 cruise transect in the North Atlantic Ocean corresponded to thebautii like populations.
Niche differentiation

21. IN PROCESS…
High-throughput metatranscriptome sequencing to examine transcriptional patterns and relative gene expression in order to understand physiological ecology of surface v subsurface populations (already extracted and waiting for the sequences to start HAVING FUN!)
Columbia genome center

22. Thank You! Sonya Dyhrman Abby Heithoff Dyhrman´s lab:
Harriet Alexander
Hanna Jon-Warren
Sheean Haley
Julia Diaz
Louie Wurch
Solange Duhamel
Elise Olson
Dennis McGillicuddy
Thank You!
FUNDING:
Fundación Ramón Areces (SPAIN).
C-MORE
National Science Fundation.

23. C1
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