Dissolved inorganic carbon fixation of Thaumarchaeota vs. Bacteria in the meso- and

upper bathypelagic waters of the world´s oceans differenciated with the use of metabolic inhibitors

Marta M. Varela, Gerhard Herndl, Eva Sintes, Eva Teira, & Josep Gasol

Instituto Español de Oceanografía-IEO. CO-CoruñaUniversidade de VienaUniversidade de Vigo.

Institut de Ciències del Mar. CMIMA , CSIC

Recent studies suggest that unidentified prokaryotes fix inorganic carbon at significant rates in the dark ocean (Reinthaler et al. 2010; Varela et al. 2011)

Genomic and physiological studies have shown evidences that Thaumarchaeota should play an important role in the carbon cycle (Herndl et al. 2005; Walker et al. 2010)

0 10 20 30 40 50

Subsurface

upper O2-min

lower O2-min

MSOW

AAIW

upperNEADW

lowerNEADW

DI14C-positive cells in percent

0 10 20 30 40 50

Subsurface

upper O2-min

lower O2-min

MSOW

AAIW

upperNEADW

lowerNEADW

Wat

er M

ass

DI14C-positive cells in percent

Picoplankton

Bacteria

Crenarchaeota

eastern-Atlantic mid-Atlantic

WHY?

Some Bacteria showed high chemoautotrophic activityAlonso-Sáez et al. 2010, Varela et al. 2011)

Global ocean prokaryotic community composition:

Major groups of prokaryotes: Bacteria, Eury- and ThaumarchaeotaBacteria: SAR 11, SAR202, Alteromonas, SAR 406, SAR324

Global ocean and deep water bulk uptake of bicarbonate, differentiating Bacteria and Thaumarchaeota contribution (Yokokawa et al.

Single-cell identification of active dark bicarbonate fixers

To examine the contribution of Thaumarchaeota vs. Bacteria to total prokaryotic fixation of dissolved inorganic carbon (DIC) in the meso- and upper batypelagic waters of the world oceans.

GOAL OF THE STUDY:

Radiolabeled Substrate

(14C)

Incubation

Fixation &Filtration Radioactive

cell

Non-Radioactive cell

target

probe

Prokaryotic community composition: by Fluorescence In Situ Hybridization (CARD-FISH):

HOW ?

Group Specific Activity: by microautoradiography combined with FISH (MICRO-CARD-FISH)

Dissolved inorganic carbon (DIC) fixation: incorporation of 14C-bicarbonate, by using Erythromycin to discriminate archaeal from bacterial activity (Yokokawa et al. 2012)

Bicarbonate assimilation

MICRO-CARD-FISH

Malaspina 2010 Circumnavigation Expedition: Global Change and Biodiversity Exploration of the Global Ocean" (December 2010-July 2011)

STUDY SITE

150º 100º 50º 0º 50º 100º 150º

50º

0º

50º

4652 57 60 66

8689

93

98105 110 116

124130132135138

143

E EWWW 0

N

S

EQ

E 8000

6000

4000

2000

0

2000

4000

6000

8000

0

Pacific Ocean

AtlanticOcean

Indian Ocean

Indian Ocean: 46; 52; 57; 60; 66

Pacific Ocean: 86; 89; 93; 98; 105; 110; 116; 124

Atlantic Ocean: 130; 132; 135; 138; 143

Bacteria vs. Eury- and Thaumarchaeota + cells (% of DAPI counts):

WHAT ?

Indian Ocean Pacific Ocean Atlantic Ocean

n=9 n=

61%11%2%

26%

55%

12%3%

30%

n= 4

Mes

opel

agic

Bath

ypel

agic

61%16%

6%

17%

67%

26%

1%

6%

SAR11, SAR 202, Alteromonas, SAR 406, SAR 324 + cells (% of Eub + cell):

Indian Ocean Pacific Ocean Atlantic Ocean

n= 11

16%5%

3%

10%

8%

58%

Mes

opel

agic

n= 4

19%

9%

10%

9%10%

43%

Bath

ypel

agic

n=9

24%

3%

16%

21%

7%

29%

30%

12%

19%

18%

3%18%

n= 13

DIC fixation by the prokaryotic community(bulk uptake of 14C-bicarbonate):

0

200

400

600

800

1000

1200

1400

1600

0.00 0.01 0.10 1.00 10.00 100.00

control

Erythromycin

0.00 0.01 0.10 1.00 10.00 100.00

control

Erythromycin

0.00 0.01 0.10 1.00 10.00 100.00

control

Erythromycin

De

pth

(m

)

DI14C fixation (µmol C m-3 d-1)

Indian Ocean Pacific Ocean Atlantic Ocean

Contribution of Bacteria vs. Thaumarchaeota to DIC fixation :

0

200

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100D

epth

(m

)Contribution to DI14C incorporation rate (%)

Bacteria Thaumarchaeota

Bacteria ThaumarchaeotaBacteria Thaumarchaeota

Indian OceanPacific OceanAtlantic Ocean

% of Bacteria or Thaumarchaeota incorporating bicarbonate:

SUMMARY Bacteria dominated throughout the water column in the three world oceans (54% of the total DAPI counts) and did not change with depth.By contrast, the abundance of Cren was generally higher in the bathypelagic layers than in the mesopelagic waters (reaching values up to 29% of the total DAPI counts in the Pacific Ocean).

SAR11 contributed 8, 33 and 18% to total prokaryotic inorganic carbon incorporation in the Indian, Pacific and Atlantic world oceans, respectively, over the entire water column.

Archaea contributed 8, 33 and 18% to total prokaryotic inorganic carbon incorporation in the Indian, Pacific and Atlantic world oceans, respectively, over the entire water column.

The Archaea contribution to total prokaryotic carbon incorporation tends to increases with depth, particularly at the Atlantic waters below 1000m and in the lower mesopelagic zone of the Pacific Ocean.

Single-cell analysis

We thank all the people involved in the MALASPINA 2010 project who helped with the cruise preparation and sampling.

ACKNOWLEDGMENTS

· We also thank the officers and crew of the R/V Hespérides, as well as the staff of the Technical Support Unit (UTM), for their support during the work at sea.

·This research was supported contracts MALASPINA (CSD 2008-00077), BIO-PROF and MODUPLAN.