Carbon dioxide emissions from the littoral zone of a Chinese reservoir

Abstract

The continuous increase in the number of reservoirs globally has raised important questions about the environmental impact of their greenhouse gases emissions. In particular, the littoral zone may be a hotspot for production of greenhouse gases. We investigated the spatiotemporal variation of CO2 flux at the littoral zone of a Chinese reservoir along a wet-to-dry transect from permanently flooded land, seasonally flooded land to non-flooded dry land, using the static dark chamber technique. The mean total CO2 emission was 346 mg m-2 h-1 and the rate varied significantly by water levels, months and time of day. The spatiotemporal variation of flux was highly correlated with biomass, temperature and water level. Flooding could play a positive role in carbon balance if water recession occurs at the time when carbon gains associated with plant growth overcomes the carbon loss of ecosystem. The overall carbon balance was analysed using cumulative greenhouse gases fluxes and biomass, bringing the data of the present study alongside previously published, simultaneously measured CH4 and N2O fluxes. For the growing season, 12.8 g C m-2 was absorbed by the littoral zone. Taking CH4 and N2O into the calculation showed that permanently flooded sites were a source of greenhouse gases, rather than a sink. Our study emphasises how water level fluctuation influenced CO2, CH4 and N2O in different ways, which greatly affected the spatiotemporal variation and emission rate of greenhouse gases from the littoral zone.