| 英文摘要： |
A floodplain lake system can be described as a water conveyance-type lake system that is subject to high water-level fluctuations (WLFs). This study investigated the effects of WLF on the nutrient status and the gross primary productivity (GPP) of phytoplankton in Lake Poyang, a large floodplain-lake system in China. This study hypothesized that WLF is the key controlling regulator of the lake's nutrient status, phytoplankton growth and GPP, driven by its influence on the lake's hydrological connectivity in combination with water-flow velocity as well as other environmental parameters. The results showed that the intra-annual water levels in this lake varied from 7.61 m to 20.82 m while inter-annual water levels significantly decreased throughout 1989-2018 (P < 0.05). Except for pH, most environmental variables and nutrients differed significantly each season. Mean GPP and chlorophyll a (Chl a) concentration during the water rising period was clearly higher compared to the dry season, wet season and falling period. Moreover, nutrient concentration was the main determining factor of phytoplankton growth and GPP during different periods, while water temperature (WT) also played a key role in influencing phytoplankton biomass and GPP during the water rising period. There was also a direct correlation between WLF and GPP during the water rising period, and WLF significantly affected nutrient concentration, subsequently impacting GPP. This study can benefit our overall knowledge of hydrological and ecological dynamics in floodplain-lake systems, while providing an important reference for policymakers in the management of dams and water quality in floodplain-lake systems globally. |
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