Modes of carbon fixation in an arsenic and CO₂-rich shallow hydrothermal ecosystem

TY - JOUR

T1 - Modes of carbon fixation in an arsenic and CO2-rich shallow hydrothermal ecosystem

AU - Callac, Nolwenn

AU - Posth, Nicole R.

AU - Rattray, Jayne E.

AU - Yamoah, Kweku K. Y.

AU - Wiech, Alan

AU - Ivarsson, Magnus

AU - Hemmingsson, Christoffer

AU - Kilias, Stephanos P.

AU - Argyraki, Ariadne

AU - Broman, Curt

AU - Skogby, Henrik

AU - Smittenberg, Rienk H.

AU - Fru, Ernest Chi

PY - 2017/12/1

Y1 - 2017/12/1

N2 - The seafloor sediments of Spathi Bay, Milos Island, Greece, are part of the largest arsenic-CO2-rich shallow submarine hydrothermal ecosystem on Earth. Here, white and brown deposits cap chemically distinct sediments with varying hydrothermal influence. All sediments contain abundant genes for autotrophic carbon fixation used in the Calvin-Benson-Bassham (CBB) and reverse tricaboxylic acid (rTCA) cycles. Both forms of RuBisCO, together with ATP citrate lyase genes in the rTCA cycle, increase with distance from the active hydrothermal centres and decrease with sediment depth. Clustering of RuBisCO Form II with a highly prevalent Zetaproteobacteria 16S rRNA gene density infers that iron-oxidizing bacteria contribute significantly to the sediment CBB cycle gene content. Three clusters form from different microbial guilds, each one encompassing one gene involved in CO2 fixation, aside from sulfate reduction. Our study suggests that the microbially mediated CBB cycle drives carbon fixation in the Spathi Bay sediments that are characterized by diffuse hydrothermal activity, high CO2, As emissions and chemically reduced fluids. This study highlights the breadth of conditions influencing the biogeochemistry in shallow CO2-rich hydrothermal systems and the importance of coupling highly specific process indicators to elucidate the complexity of carbon cycling in these ecosystems.

AB - The seafloor sediments of Spathi Bay, Milos Island, Greece, are part of the largest arsenic-CO2-rich shallow submarine hydrothermal ecosystem on Earth. Here, white and brown deposits cap chemically distinct sediments with varying hydrothermal influence. All sediments contain abundant genes for autotrophic carbon fixation used in the Calvin-Benson-Bassham (CBB) and reverse tricaboxylic acid (rTCA) cycles. Both forms of RuBisCO, together with ATP citrate lyase genes in the rTCA cycle, increase with distance from the active hydrothermal centres and decrease with sediment depth. Clustering of RuBisCO Form II with a highly prevalent Zetaproteobacteria 16S rRNA gene density infers that iron-oxidizing bacteria contribute significantly to the sediment CBB cycle gene content. Three clusters form from different microbial guilds, each one encompassing one gene involved in CO2 fixation, aside from sulfate reduction. Our study suggests that the microbially mediated CBB cycle drives carbon fixation in the Spathi Bay sediments that are characterized by diffuse hydrothermal activity, high CO2, As emissions and chemically reduced fluids. This study highlights the breadth of conditions influencing the biogeochemistry in shallow CO2-rich hydrothermal systems and the importance of coupling highly specific process indicators to elucidate the complexity of carbon cycling in these ecosystems.

U2 - 10.1038/s41598-017-13910-2

DO - 10.1038/s41598-017-13910-2

M3 - Journal article

C2 - 29089625

SN - 2045-2322

VL - 7

JO - Scientific Reports

JF - Scientific Reports

M1 - 14708

ER -