Dr. Fuh-Kwo Shiah

Research Center for Environmental Changes, Academia Sinica

Seminar 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 (Jun~Sep) 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.