Extreme Weather Events Enhance DOC Consumption in a Subtropical Freshwater Ecosystem: A Multiple-Typhoon Analysis

Chao-Chen Lai; Chia-Ying Ko; Eleanor Austria; Fuh-Kwo Shiah

doi:10.3390/microorganisms9061199

Extreme Weather Events Enhance DOC Consumption in a Subtropical Freshwater Ecosystem: A Multiple-Typhoon Analysis

Microorganisms. 2021 Jun 1;9(6):1199. doi: 10.3390/microorganisms9061199.

Authors

Chao-Chen Lai¹, Chia-Ying Ko^{2

3

4}, Eleanor Austria⁵, Fuh-Kwo Shiah^{1

6

7}

Affiliations

¹ Research Center for Environmental Changes, Academia Sinica, Taipei 115, Taiwan.
² Institute of Fisheries Science, National Taiwan University, Taipei 10617, Taiwan.
³ Department of Life Science, National Taiwan University, Taipei 10617, Taiwan.
⁴ Department of Biochemical Science and Technology, National Taiwan University, Taipei 10617, Taiwan.
⁵ Biology Department, Adamson University, Ermita, Manila 1000, Philippines.
⁶ Institute of Oceanography, National Taiwan University, Taipei 10617, Taiwan.
⁷ Institute of Marine Environment and Ecology, National Taiwan Ocean University, Keelung 202, Taiwan.

Abstract

Empirical evidence suggests that the frequency/intensity of extreme weather events might increase in a warming climate. It remains unclear how these events quantitatively impact dissolved organic carbon (DOC), a pool approximately equal to CO₂ in the atmosphere. This study conducted a weekly-to-biweekly sampling in a deep subtropical reservoir in the typhoon-prevailing season (June to September) from 2004 to 2009, at which 33 typhoons with distinctive precipitation (<1~362 mm d^-1) had passed the study site. Our analyses indicated that the phosphate (i.e., DIP; <10~181 nMP) varied positively with the intensity of the accumulated rainfall 2-weeks prior; bacteria growth rate (0.05~3.68 d^-1) behaved as a positive function of DIP, and DOC concentrations (54~119 µMC) changed negatively with bacterial production (1.2~26.1 mgC m^-3 d^-1). These implied that the elevated DIP-loading in the hyperpycnal flow induced by typhoons could fuel bacteria growth and cause a significant decline of DOC concentrations. As the typhoon's intensity increases, many mineral-limited lentic freshwater ecosystems might become more like a CO₂ source injecting more CO₂ back to the atmosphere, creating a positive feedback loop that might generate severer extreme weather events.

Keywords: bacteria; climatic changes; microbial ecology; organic carbon cycling; reservoir; typhoons.