Abstract
This research was conducted to understand whether phosphorus limits the phytoplankton production in the South China Sea (SCS). In the nutrient enrichment experiments nitrate and phosphate were supplemented to surface sea water and the enhancement of chlorophyll a concentration during incubation was observed. Seasonal field survey was conducted to measure ambient abundance of phosphorus including phosphate (SRP) and dissolve organic phosphorus (DOP), as well as alkaline phosphatase activity (APA) in the nautral sea water in the contiential shelf and basin of the SCS.
Except at the contiential shelf in summer and the mouth of Zhu Jiang River in fall, the nutrient concentration of surface water was low in the SCS. The average¡£NO3+NO2¡¤was 20 nM (fall) - 360 nM (winter ). The average SRP concentration was 16 nM (fall) - 87 nM (winter). The average DOP concentration was 0.08 £gM (summer)- 0.25 £gM (winter). The ¡£NO3+NO2¡¤/ SRP ratio was smaller than the Redfield N/P ratio of 16. The average chlorophyll a concentration (Chl a) was 0.13 £gg l-1 (summer) - 0.48 £gg l-1 (winter). The average concentration of the particlulate organic carbon (POC) was 4.58 £gM (spring) - 8.11 £gM (winter). The average APA was 16 n mol l-1 h-1 (fall) - 87 n mol l-1h-1 (winter). The average of APA/Chl a was 33.94 n mol £gg -1 h-1 (winter) - 97.22 n mol £gg -1 h-1 (spring).
The results of the enrichment experiment show that the phosphorus deficiency was observed on the contiential shelf in the summer of 2001 and at the mouth of Zhu Jiang in the fall of 2002. The common characteristics of the phosphorus deficient regions were low salinity (29.90- 30.87 psu ), high¡£NO3+NO2¡¤(1.31 - 3.01 £gM) , and a ¡£NO3+NO2¡¤/ SRP ratio higher than 16. Chl a increased significantly (p<0.05) by the enrichments of phosphorus. In spring and winter when all regions were N-limited, N enrichment significantly (p<0.05) increased Chl a. In fall, all the contiential shelf region except the mouth of Zhu Jiang River, the slope and basin regions were NP co-limited. The Bashi Strait in summer was also NP co-limited.
P-limitation that was seen in the contiential shelf SCS and at Zhu Jiang River mouth, was probably caused by the influence of river discharge. N/P, SRP or APA were not effective parameters to assess whether marine phytoplankton growth was limited phosphorus, nitrogen or both. In the SCS, the P-limited water masses were, in general, low in salinity, high in¡£NO3+NO2¡¤,Chl a,¡£NO3+NO2¡¤ / Chl a, APA and a N/P ratio higher than 16. The water masses that were N-limited was high in salinity, and low in¡£NO3+NO2¡¤, Chl a,¡£NO3+NO2¡¤/ Chl a and APA, as well as a N/P ratio smaller than 16. The water masses that were nitrogen and phosphorus co-limited were different from the N-limited ones in that they were low in SRP, SRP/Chl a, and DOP. The SRP and DOP concentration in the NP co-limited region were 11 - 28 nM and 0.09 - 0.23
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0909104-151640 |
| Date | 09 September 2004 |
| Creators | Hwang, Gloria |
| Contributors | Yuh-ling Lee Chen, Tse-Min Lee, Jia-Jang Hung, Houng-Yung Chen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0909104-151640 |
| Rights | not_available, Copyright information available at source archive |
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