Southward spreading of the Changjiang Diluted Water in the La Niña spring of 2008.

The La Niña of 2007/2008 was particularly strong, so was the southward flow of the cold, nutrient-rich Changjiang (Yangtze River) Diluted Water (CDW) when the winter monsoon started to blow in the fall. Here we use shipboard data in 2008 in two transects, one in the southwestern East China Sea and one in the southern Taiwan Strait, to show that as late as April in 2008 the CDW was still clearly identifiable when the winter monsoon had weakened. Waters as cold as 16 °C with a salinity lower than 30 still occupied the southwestern East China Sea. Waters of 17 °C and S < 32 could also be found off the coast of China in the central Taiwan Strait. The concentration of NO3 + NO2 was higher than 18 µmol L-1 at both places, which was as much as 40 times higher than the northward moving South China Sea (SCS) water to the east. As a result, the Changjiang River plume may be a significant source of nutrients, particularly N, to the oligotrophic, N-poor SCS, especially in the La Niña years. Indeed, colder and more turbid CDW was more intense and went farther south in 2008 compared with the normal springs of 2006, 2007 and 2009.

East China Sea increasingly gains limiting nutrient P from South China Sea.

The Taiwan Strait (TS) directly connects two of the richest fishing grounds in the world - the East China Sea (ECS) and the South China Sea (SCS). Carbon and nutrient supplies are essential for primary production and the Yangtze River is an important source for the ECS. However the ECS is severely P-limited. The TS transports an order of magnitude more carbon and a factor of two more phosphate (P) to the ECS than the Yangtze River does. To evaluate the temporal variability of these supplies, the total alkalinity (TA), dissolved inorganic carbon (DIC), nitrate plus nitrite (N), P, and silicate (Si) fluxes through the TS were estimated using empirical equations for these parameters and the current velocity, which was estimated using the Hybrid Coordinate Ocean Model (HYCOM). These empirical equations were derived from in situ salinity and temperature and measured chemical concentrations that were collected during 57 cruises (1995-2014) with a total of 2096 bottle samples. The 24-month moving averages of water, carbon, and nutrient fluxes significantly increase with time, so does the satellite chlorophyll a concentration. More importantly, the increased supply of the badly needed P from the TS is more than that from the Yangtze River.