Jianfang Chen¹, Lianfu Zheng¹, Mingming Jin¹, Martin G Wiesner² and How Kin Wong²

¹Second Institute of Oceanography of SOA, Hangzhou 310012, P R China, Tel: 0086-571-88076924 ext. 2483, Fax: 0086-571-88071539, E-mail: chen_jianfang@sio.zj.edu.cn; jfchen@hzcnc.com, and ²Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, Germany

Responses of particle fluxes and sediment records to upper layer nutrients distribution: A case study from the South China Sea

Linking of upper ocean and bottom response largely determines the possibility and credibility of utilizing geochemical or microfossil indicators as paleo-environment proxies. Based on two cruises in June/July 1998 and January 1999, upper layer thermocline distribution and nutrient limitation in winter/summer monsoon periods were discussed in three up-willing areas as well as other areas in the South China Sea. The upper ocean physical-chemical conditions were compared with long-time series sediment trap based particle fluxes as well as surface sediment records. In winter monsoon periods physical-chemical up-willing index was observed off the Sunda shelf and northwest off Luzon, lower DIN/P (6.1) and Si/P (7.4) indicated that Si and DIN might be limitation factors for the phytoplankton. In summer monsoon periods up-willing was observed off Vietnam and phosphorous limitation might exist in upper layer. Very high in-situ measured Chl a and primary productivity were found off Sunda shelf and off Vietnam in both winter and summer periods and higher values was observed off Luzon in winter and off Palawan and southwest off Taiwan in summer. General pattern of particle flux in the South China Sea is that higher fluxes occur in monsoon periods and winter monsoon induced much more particle flux than that in summer monsoon, especially in northern part of the South China Sea. Low CaCO₃/Opal in particulate matter was observed in winter monsoon periods and silicate limitation existed in winter upper layer waters suggest that monsoon related dust input from Chinese continent may play a trigger for phytoplankton bloom and downward particle fluxes in the South China Sea in winter. Sediment signals such as organic carbon, opal, organic carbon isotope and organic phosphorous in surface sediments response well to the upper layer condition in the southern South China Sea and off Vietnam, but there bad relationships between upper and bottom in northeast up-willing area of the South China Sea. The reason might be advent transport of particles such nepheloid or turbidity in the northern slope of the South China Sea.