A functional group approach reveals important fish recruitments driven by flood pulses in floodplain ecosystem

Abstract

The periodical flood pulses, assisting by the connectivity between rivers and lakes in floodplain ecosystems, are of paramount importance in underpins fish meta-communities. Regardless of the unprecedented anthropogenic disturbances on natural flood regimes, there is limited understanding for the response of fish assemblages to flood pulses. Most studies documented the issue sorely on floodplain rivers or floodplain lakes, but the dynamics of fish communities in the transitional floodplains accounting for both lentic and lotic environments are rarely reported. Here we measure temporal (high and low water seasons) and spatial (lotic and lentic environments) patterns of fish assemblages in the transitional floodplain between the Yangtze River and Lake Caizi using taxonomic and functional group metrics. Our results demonstrated significantly variations in fish community composition among different environments between high and low water seasons. During flooding season in high water phase, we observed significantly patchy population recruitments of riverine fish species. Then in low water season, widespread lake residents dominated the lentic environments due to their higher environment tolerance. Benefitting from the functional group measurement, we identified three flooding related functional groups i.e., G2, G9 and G10 (consisting of riverine catfishes, gudgeons, and loaches), that may bear the brunt of natural flood pulses alterations. Despite the significant variations of richness in taxonomic diversity, we detected higher sensitivity of functional diversity, since three functional diversity indices were significantly higher in high water season. This findings demonstrated important functional recruitments triggered by flood pulses, highlighting a pressing need to sustain natural flood regime with hydrological connectivity for better conservation of fish assemblages in floodplain ecosystem.