Inter-shelf nutrient transport from the East China Sea as a major nutrient source supporting winter primary production on the northeast South China Sea shelf

Abstract

Abstract. The East China Sea (ECS) and the South China Sea (SCS) are two major marginal seas of the North Pacific with distinct seasonal variations of primary productivity. Based upon field observations covering both the ECS and the northern SCS (NSCS) during December 2008-January 2009, we examined southward long-range transport of nutrients from the ECS to the northeastern SCS (NESCS) carried by the China Coastal Current (CCC) driven by the prevailing northeast monsoon in wintertime. These escaped nutrients from the ECS shelf, where primary production (PP) was limited in winter, might however refuel the PP on the NESCS shelf at lower latitude, where the water temperature remained favorable, but river-sourced nutrients were limited. By combining the field observation of nitrate+nitrite (NO 3 +NO 2 , DIN) with our best estimate of volume transport of the CCC, we derived a first-order estimate for DIN flux of 1430 ± 1024 mol s −1 . Under the assumption that DIN was the limiting nutrient, such southward DIN transport would have stimulated 8.84 ± 6.33 × 10 11 gC of new production (NP), accounting for 33-74 % of the NP or 14-22 % of PP in winter on the NESCS shelf shallower than 100 m.

Seasonal shifts in the contributions of the Changjiang River and the Kuroshio Current to nitrate dynamics in the continental shelf of the northern East China Sea based on a nitrate dual isotopic composition approach

“…Shelf mixed water (SMW) forms from these with a mixing ratio that varies with location and season (e.g., Zhang et al, 2007a). In summer, the nutrient-rich Changjiang buoyant plume disperses eastward and reaches as far as the shelf break (Isobe et al, 2004), whereas in winter, when precipitation is limited and a northerly wind prevails, CDW flows southward along the coast (Chen, 2008;Han et al 2013). In summer, Taiwan Strait Warm Water (TSWW) flows dominantly northeastward along with KSW, and these waters merge northeast of Taiwan due to impingement of the Kuroshio on the continental shelf and by onshore intrusion caused by frontal eddy motion around the shelf edge (Zhu et al, 2004;Guo et al, 2006;Lee and Matsuno, 2007).…”

Phytoplankton dynamics driven by vertical nutrient fluxes during the spring inter-monsoon period in the northeastern South China Sea

“…Wind-driven coastal upwelling, river discharge and inter-shelf nutrient transport were important mechanisms supplying nutrients to the euphotic zone of the nSCS (Liu et al, 2002;Gan et al, 2010;Han et al, 2013), while their contributions to primary production were mostly limited to coastal regions as these nutrients would be mostly utilized in the coastal waters before reaching the large area of the nSCS. Kuroshio intrusion would dilute the nSCS waters with the low-nutrient North Pacific waters (Farris and Wimbush, 1996), which appeared to be much weaker during April-September (Centurioni et al, 2004).…”

Dissolved silicon isotopic compositions in the East China Sea: Water mass mixing vs. biological fractionation

“…Rich supplies of nutrients from the upwelling of Kuroshio subsurface water (Chen 1996) as well as the Changjiang discharge (Li et al 2007) stimulate high primary production (PP) on the East China Sea shelf resulting in one of the most productive areas of the world's oceans (Liu et al 2010). Moreover, the East China Sea is characterized by a distinct seasonal pattern of warm summers (22.0-28.08C) and colder winters (9.0-21.08C) (Han et al 2013). PP in winter is approximately one order of magnitude lower than the 200-1000 mg C m 22 d 21 reached in summer, primarily due to poor growth conditions such as reduced light availability (Gong et al 2003;Chiang et al 2004;Liu et al 2010).…”