滇池浮游植物碳氮同位素时空分布特征及其影响因子分析

通过对旱季、旱雨季过渡期和雨季3个不同时期滇池浮游植物 δ13C、δ15N的研究发现,滇池浮游植物δ13C、δ15N存在显著的时空分布特征.从旱季、过渡期到雨季,浮游植物δ13C值分别为-20.44‰±0.72‰、-17.32‰±1.09‰和-15.92‰±1.74‰,呈逐渐升高趋势;而浮游植物δ15N值的季节变化模式...

Spatio-temporal distribution and influencing factors of stable carbon and nitrogen isotopes of phytoplankton in Dianchi Lake

A comparative study of δ¹³C and δ¹⁵N values of phytoplankton in Dianchi during the dry, transitional and rainy seasons showed that the δ¹³C and δ¹⁵N levels of phytoplankton were characterized by significant spatial and temporal fluctuations. During the dry, transitional and rainy seasons, the δ¹³C of phytoplankton were respectively at -20.44‰±0.72‰, -17.32‰±1.09‰ and -15.92‰±1.74‰, showing a gradually increasing trend. However, the opposite trend was recorded for the seasonal variation of δ¹⁵N levels in phytoplankton, because in rainy season the level was significantly lower (13.55‰±0.85‰) than in the transitional period (15.02‰±1.12‰), and in the dry season (15.02‰±1.12‰). The average of the spatial distribution of the δ¹³C levels in phytoplankton is 13.17‰, with an upper level in the south basin and a lower level in the north basin. For the δ¹⁵N levels of spatial distribution in phytoplankton, the average was 11.37‰, with a high value n the central basin and lower values in the southern and northern basins of the lake. About the level influencing factors, the statistical analyses showed that the δ¹³C value of phytoplankton in Dianchi was strongly related to multiple factors such as water temperature, precipitation, electrical conductivity and pH value, indicating that δ¹³C level of phytoplankton was significantly affected by cell growth rate and inorganic carbon sources. The seasonal variation in the δ¹⁵N values of phytoplankton in the lakes was mainly related to precipitation, and to the total nitrogen, and total phosphorus levels in the waters. The spatial variation in the δ¹⁵N was consistent with the spatial pattern of catchment land uses in Dianchi. This indicated that urban domestic sewage still remains an important pollution source of Dianchi, while agricultural fertilizer and other non-point source pollution played an important role in modulating both spatial and temporal variation of the phytoplankton δ¹⁵N levels. Therefore, spatial patterns of land use and seasonal variations in precipitation, were importantly affecting the ecosystem nutrient cycling and isotopic levels in the biota of the Dianchi lake.