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

A Q Han,J Y Hu,C.-T A Chen,S.-J Kao,J P Gan,F Gong,L F Wang,M H Dai,L Wang,H Lin,X Z Zhao,S Jan,Q Li

doi:10.5194/bg-10-8159-2013

A Q Han, J Y Hu + Show 11 more

Open Access

https://doi.org/10.5194/bg-10-8159-2013

Copy DOI

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 (NO3+NO2, 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 × 1011 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.

Highlights

The continental shelf is well known for its high biological production, due to the abundant nutrients sourced from the land via river discharge and/or supplied through coastal upwelling and shoreward cross-shelf transport (Wollast, 1991, 1993; Ladd et al, 2005; Whitney et al, 2005; Sugimoto et al, 2009)
The former water masses with salinity < 33.0 may be grouped into two: one was the Pearl River plume (PRP) featured by higher temperature, and the other was the China Coastal Current (CCC) characterized by a larger salinity range and lower temperature
This study has highlighted that the monsoonal wind-driven CCC might be a primary conduit for nutrient transport from the East China Sea (ECS) to the northeastern SCS (NESCS) shelf

Summary

Introduction

The continental shelf is well known for its high biological production, due to the abundant nutrients sourced from the land via river discharge and/or supplied through coastal upwelling and shoreward cross-shelf transport (Wollast, 1991, 1993; Ladd et al, 2005; Whitney et al, 2005; Sugimoto et al, 2009). Another possible transport pathway to redistribute dissolved and particulate nutrients and other materials is through alongshore currents, which can often be observed along the isotherms, featured with significant volume transports over long distance (Liu et al, 2000; Kao et al, 2003; Keafer et al, 2005; Whitney et al, 2005; Liu et al, 2007; Chen, 2008; Guo et al, 2012). Hydrographic data characterize the China Coastal Current (CCC), which is driven by the northeast winter monsoon, to be one of the major water

Methods

Results

Conclusion