Seasonal and inter-annual variability in the East China Sea and Southern Yellow Sea ecosystem (1998-2012)

Abstract

East China Sea (ECS) and southern Yellow Sea (SYS) ecosystems have undergone drastic changes over the past two decades. The changes in the ecosystems are attributable to the on-going anthropogenic and natural stressors as well as the recent in-land activities such as the implementation of the world’s largest dam and the gigantic water-management scheme in China. Here, we assessed the long-term spatial and temporal variability in the marine primary productivity using SeaWiFS and MODIS-aqua merged remotely sensed data from 1998-2012. We also analyzed the decadal changes in chlorophyll-a, photosynthetically active radiation, sea surface temperature, euphotic depth, as well as the Changjiang river discharge (CRD) in the study area. Our results indicate that the ECS and SYS primary productivity can be characterized by high spatial and temporal heterogeneity. For instance, despite the reduction of the CRD after the operation of the Three Gorges Dam, we observed an increase in productivity in the vicinity of the river mouth as the nutrient loading has continuously increased. We, however, also observed a decrease in the primary productivity in the offshore regions where the CRD influence was greatly reduced after the operation of the dam. In contrast to the coastal water, the slope region showed a gradual decrease in the productivity, mainly due to warming while some region did not show a clear trend as the other regions. in-land activities such as the implementation of the world’s largest dam and the gigantic water-management scheme in China. Here, we assessed the long-term spatial and temporal variability in the marine primary productivity using SeaWiFS and MODIS-aqua merged remotely sensed data from 1998-2012. We also analyzed the decadal changes in chlorophyll-a, photosynthetically active radiation, sea surface temperature, euphotic depth, as well as the Changjiang river discharge (CRD) in the study area. Our results indicate that the ECS and SYS primary productivity can be characterized by high spatial and temporal heterogeneity. For instance, despite the reduction of the CRD after the operation of the Three Gorges Dam, we observed an increase in productivity in the vicinity of the river mouth as the nutrient loading has continuously increased. We, however, also observed a decrease in the primary productivity in the offshore regions where the CRD influence was greatly reduced after the operation of the dam. In contrast to the coastal water, the slope region showed a gradual decrease in the productivity, mainly due to warming while some region did not show a clear trend as the other regions.