New publication shows influence of sea animal colonies on Antarctic tundra OCS fluxes

(September 16, 2023) In this interdisciplinary study just published in Communications Earth & Environment, former visiting scholar Dr. Wanying Zhang et al. report how the Antarctic tundra shifts from a sink to a source of carbonyl sulfide (OCS) under the influence of sea animal colonies.

“Sea animal colonies enhance carbonyl sulfide emissions from coastal Antarctica”, by Wanying Zhang, Renbin Zhu, Yi Jiao, Robert Rhew, Bowen Sun, Riikka Rinnan and Zeming Zhou. https://www.nature.com/articles/s43247-023-00990-4

Carbonyl sulfide (OCS) is the most abundant reduced sulfur compound in the atmosphere and has a lifetime of 2-4 years in the troposphere. Its injection to the stratosphere yields sulfate aerosols which reflect incoming solar radiation, thereby impacting Earth’s radiative balance. In addition, OCS has potential as a tracer of gross primary production (GPP). It is consumed irreversibly through interaction with carbonic anhydrase, the enzyme that catalyzes the reaction of CO₂ and H2O in plant leaves on the way to carbon fixation. However, the picture gets increasingly complex as COS also has bidirectional fluxes in the terrestrial biosphere.

In this work, Dr. Wanying Zhang combines laboratory core incubations with field measurements, enzymatic activity measurements, biogeochemical measurements and microbiology to get a systematic view of what is happening in the Antarctic tundra, with and without sea animal input. Wanying finds that the seals and penguins transport and deposit so much organic sulfur to the tundra that they dramatically change the biogeochemical cycling of sulfur, including the microbial abundance and enzymatic activities in the soil. The result is a conversion of the tundra from a sink to a source of carbonyl sulfide, an example of how large animals can impact ecosystem fluxes of trace gases.

Caption: From Figure 5 of the paper, this is a conceptual drawing of the potential mechanisms of OCS production and degradation in the Antarctic tundra, illustrating the potential role of sea animal colonies in affecting organic sulfur inputs.