A source of isotopically light organic carbon in a low-pH anoxic marine zone
Vargas, C.A.; Cantarero, S.I.; Sepúlveda, J.; Galán, A.; De Pol-Holz, R.; Walker, B.; Schneider, W.; Farias, L.; D’Ottone, M.C.; Walker, J.; Xu, X.; Salisbury, J. (2021). A source of isotopically light organic carbon in a low-pH anoxic marine zone. Nature Comm. 12(1): 1604. https://dx.doi.org/10.1038/s41467-021-21871-4
In: Nature Communications. Nature Publishing Group: London. ISSN 2041-1723; e-ISSN 2041-1723, more
|   |
| Authors | | Top |
- Vargas, C.A.
- Cantarero, S.I.
- Sepúlveda, J.
- Galán, A.
|
- De Pol-Holz, R.
- Walker, B.
- Schneider, W.
- Farias, L.
|
- D’Ottone, M.C.
- Walker, J.
- Xu, X.
- Salisbury, J.
|
| Abstract |
Geochemical and stable isotope measurements in the anoxic marine zone (AMZ) off northern Chile during periods of contrasting oceanographic conditions indicate that microbial processes mediating sulfur and nitrogen cycling exert a significant control on the carbonate chemistry (pH, AT, DIC and pCO2) of this region. Here we show that in 2015, a large isotopic fractionation between DIC and POC, a DIC and N deficit in AMZ waters indicate the predominance of in situ dark carbon fixation by sulfur-driven autotrophic denitrification in addition to anammox. In 2018, however, the fractionation between DIC and POC was significantly lower, while the total alkalinity increased in the low-pH AMZ core, suggesting a predominance of heterotrophic processes. An isotope mass-balance model demonstrates that variations in the rates of sulfur- and nitrogen-mediated carbon fixation in AMZ waters contribute ~7–35% of the POC exported to deeper waters. Thus, dark carbon fixation should be included in assessments of future changes in carbon cycling and carbonate chemistry due to AMZ expansion. |
|
