Controls on Hypoxia
Controls on ecosystem variability and eutrophication/hypoxia has been observed as a result of physical transport of nutrients and biogeochemical substances off Oregon (Spitz et al., 2005), in the Lower St. Lawrence Estuary (Lefort et al., 2012), in the northeast Pacific (Grantham et al., 2004) and in HK waters (Li et al., 2014). Multiple–physical forcing (tides, monsoon wind, buoyancy and ambient currents) form shelf and estuarine circulations operating at different temporal and spatial scales (Zu and Gan, 2015) around the waters in the RES. They interactively regulate the residence time, nutrient transport, light availability, mixing rate (Lu and Gan, 2015), and the distribution of planktonic organisms and pollutants. These physical forcing processes are crucial to characterizing spatiotemporal variability of eutrophication/hypoxia and the overall ecosystem in the RES, yet we know very little about the circulation and the associated ecosystem response. In addition, eutrophication and hypoxia are also related to regional/global climate change, which can modulate the conditions of upstream river discharge and material flux and downstream biophysical processes in the RES.