Lake pigment characteristics and their applicability in reconstructing phytoplankton communities under irregular hydrological regulation in a floodplain lake system

Abstract

The strong hydrological characteristics and complex biochemical environment of floodplain lake systems make it difficult to obtain accurate, convincing results from sediment pigments used as paleoenvironmental indicators. Understanding pigment migration and preservation mechanisms under hydrological regulation will help explain past ecological changes in these lake systems. This study investigates phytoplankton community structure, chlorophyll distribution, and associated environmental factors throughout a hydrological cycle in Poyang Lake, China. In conjunction with pigment sediment characteristics, this study also compared pigment deposition and preservation mechanisms among three hydrological lake zones (i.e., sub-lakes, main lake, and water channel). Results show a critical loss in sediment pigment information in the main lake and the water channel resulting from the lake’s strong hydrodynamic conditions. Moreover, oxygen and sunlight had a general inhibitory effect on pigment in the overlying water, while unfavourable pH environments could affect pigments in the sediment that devoid of protective cell mechanisms. Results also show that as a biological proxy index, sub-lakes sediment pigments accurately reflect phytoplankton community structure in overlying water. Additionally, due to the relative stability of the sub-lakes environment, it can be considered the preferential lake zone from which to obtain proxy indexes in floodplain environments.