Impact of Three Gorges Dam on primary productivity in the East China Sea

Abstract

The Three Gorges Dam (TGD) on the Changjiang (Yangtze) river is the world’s largest hydropower project which began operating in June 2003. Many researchers have been concerned with the potential impact of the TGD on the adjacent marine ecosystem. For instance, Gong et al. (2006) argued that this massive dam may cause reduction in marine primary productivity in ECS by changing the supply of nutrients and sediment discharge in the area. In this study, we examined the long-term spatial and temporal trend of marine primary productivity (PP), chlorophyll-a (CHL), photosynthetically active radiation (PAR), sea surface temperature (SST) and euphotic depth (Zeu) of the ECS during last two decades (1998-2014). We also compared the cross correlation between the anomalies of Changjiang River discharge (CRD) and chlorophyll during pre-TGD (1998-2002) and post-TGD (2003-2007) to understand the sensitivity of the change and some potential influence of the ECS productivity. Our results suggest that the geographic extent of CRD influence was indeed greatly reduced after 2003. However, the large scale variability of the primary productivity did not show any correlation with the operation of the TGD nor show clear temporal and spatial trend in the ECS. Therefore, we conclude that the TGD has not reduced the primary productivity of the East China Sea as a whole.system. For instance, Gong et al. (2006) argued that this massive dam may cause reduction in marine primary productivity in ECS by changing the supply of nutrients and sediment discharge in the area. In this study, we examined the long-term spatial and temporal trend of marine primary productivity (PP), chlorophyll-a (CHL), photosynthetically active radiation (PAR), sea surface temperature (SST) and euphotic depth (Zeu) of the ECS during last two decades (1998-2014). We also compared the cross correlation between the anomalies of Changjiang River discharge (CRD) and chlorophyll during pre-TGD (1998-2002) and post-TGD (2003-2007) to understand the sensitivity of the change and some potential influence of the ECS productivity. Our results suggest that the geographic extent of CRD influence was indeed greatly reduced after 2003. However, the large scale variability of the primary productivity did not show any correlation with the operation of the TGD nor show clear temporal and spatial trend in the ECS. Therefore, we conclude that the TGD has not reduced the primary productivity of the East China Sea as a whole.