Conceptual models of dissolved carbon fluxes considering interannual typhoon responses under extreme climates in a two-layer stratified lake

Abstract

Abstract. Extreme climates affect the seasonal and interannual patterns of carbon (C) distribution due to the regimes of river inflow and thermal stratification within lentic ecosystems. Typhoons rapidly load substantial amounts of terrestrial C into subtropical small lakes, renewing and mixing the water column. We developed conceptual dissolved C models and hypothesized that allochthonous C loading and river inflow intrusion may affect the dissolved inorganic C (DIC) and dissolved organic C (DOC) distributions in a small subtropical lake under these extreme climates. A two-layer conceptual C models was developed to explore how the DIC and DOC fluxes respond to typhoon disturbances on seasonal and interannual time scales in a small subtropical lake (i.e., Yuan‒Yang Lake) while simultaneously considering autochthonous processes such as algal photosynthesis, remineralization, and vertical transportation. Monthly field samplings were conducted to measure DIC, DOC, and chlorophyll a concentrations to compare the temporal patterns of fluxes between typhoon years (2015–2016) and non-typhoon years (2017–2018). The results demonstrated that net ecosystem production was 3.14 times higher in the typhoon years than in the non-typhoon years in Yuan‒Yang Lake. The results suggested that the load of allochthonous C was the most crucial factor affecting the temporal variation of C fluxes in the typhoon years; on the other hand, the transportation rate shaped the seasonal C in the non-typhoon years due to thermal stratification within this small subtropical lake.