Seasonal Flooding Modulates Ecosystem Resource Use Efficiencies in a Coastal Brackish Wetland

Abstract

Coastal brackish wetlands are characterized by frequent seasonal flooding events, which play an important role in regulating carbon and water cycles within these ecosystems, especially as climate change is expected to amplify both the occurrence and severity of flood events. Ecosystem resource use efficiencies (RUEs) are commonly evaluated through carbon use efficiency (CUE), water use efficiency (WUE), and light use efficiency (LUE), represent integrative metrics of carbon, water, and energy dynamics, and serve as critical indicators to assess how ecosystems respond to climate change. However, the impacts of seasonal flooding on RUEs in coastal brackish wetlands remain largely uncertain. This study was based on continuous eddy covariance observations collected from a coastal brackish wetland in the Yellow River Delta during the 2019–2022 period to investigate how RUEs change over time and respond to seasonal flooding. The findings showed that the mean annual CUE, WUE, and LUE were 50%, 2.84 g C kg ⁻¹ H ₂ O, and 1.96 g C MJ ⁻¹ , respectively. By comparing the changes in RUEs before and after flooding, it was found that seasonal flooding had significantly reduced WUE and LUE by 24% and 31%, respectively. Overall, these results reveal the different responses of RUEs to seasonal flooding in coastal brackish wetlands. They elucidate how wetland ecosystems regulate carbon, water, and energy cycles under hydrological disturbances, thereby providing important scientific insights into wetland ecosystem responses and adaptations to seasonal flooding in the context of climate change.