Influence of thermal stratification on seasonal net ecosystem production
and dissolved inorganic carbon in a shallow subtropical lake
Abstract
Thermal stratification is a key physical process controlling carbon flux
from lakes to the atmosphere. Vertical profiles in shallow subtropical
lakes can vary greatly because typhoons frequently induce vertical
mixing across the entire lake due to strong winds and rapid river
flushing from inputs. Since carbon fluxes are driven by Dissolved
Inorganic Carbon (DIC), it is necessary to clarify the effect of
stratification on DIC dynamics in shallow subtropical lakes to estimate
carbon fluxes. Therefore, we aim to clarify the influence of
stratification on DIC in Yuan-Yong Lake that is a typical shallow
subtropical lake. We measured the vertical profile of water temperature
every month from July 2004 to December 2017. We applied a
three-dimensional hydrological model to estimate net ecosystem
production by combining with endmember analysis, suggesting the
possibility that large amount of DIC is stored in the lower layer from
spring to summer due to the suppression of vertical mixing by
stratification. In autumn, DIC was diluted across the layers because of
strong vertical mixing due to typhoons. Vertical profiles of DIC in
winter were confirmed to be uniform due to overturning.