Program

The Changjiang Estuary is a large-river estuary ecosystem in the East China Sea, and its plume, Changjiang Diluted Water (CDW), transports a large mass of nutrients  and supports high primary production leading to substantial eutrophication. However, relationships between nutrient delivery and phytoplankton responses have been difficult to establish, as many nutrient delivery events and algae blooms are episodic, and the CDW may expand or become detached with changing winds. In order to study the relationship between nutrient delivery events, algal blooms and estuarine metabolism dynamics, a buoy system was deployed in the CDW 9 September to10 October, 2013, with capability for physical measurements, chlorophyll a and dissolved nutrient analysis. Day-to-day nutrient increases were synchronized with salinity decreases, regulated both by the spring-neap tidal cycle and the wind field. Several specific nutrient injection periods were detected, each followed by nutrient drawn-down and chlorophyll a accumulation (algal blooms). These events appear to occur under weak wind and stable hydrodynamic conditions. . In spite of the several short-lived algal blooms, NCP was overall negative, indicating a net heterotrophic condition during the period of the study and positive reinforcement of eutrophication.