亞洲沙塵暴對臺灣東北方―黑潮海域生態系有機碳循環之影響

Effect of the Asian dust storms on organic carbon cycle in the Kuroshio Water, northeastern Taiwan

陳富群(Fu-Chun Chen)

指導教授 ： 陳仲吉

國立臺灣師範大學/理學院/生命科學研究所/碩士(2009年)

摘要

為探討亞洲沙塵暴 (Asian dust storm)如何影響黑潮海域有機碳循環的生成與變動，本研究在2006年三月沙塵暴可能侵襲期間，於臺灣東北方黑潮海域定點測站 (123° 10’ °E ; 25° 5’ °N)進行採樣研究。為便於分析比較，在此利用大氣懸浮微粒鋁元素 (Al)濃度做為判定沙塵暴事件之標準，並將其時程定義如下：「沙塵暴前」為沙塵暴侵襲之前三天的時期；「沙塵暴中」為Al濃度 > 3000 ng m-3時；「沙塵暴後」為沙塵暴侵襲之後三天的時期。研究結果顯示，「沙塵暴中」時期水體中的硝酸鹽 (0.16 ± 0.04 μM)、葉綠素甲濃度 (Chl-a；0.50 ± 0.16 mg Chl m-3)、初級生產力 (PP；9.95 ± 4.73 mg C m-3 d-1)、異營性細菌生物量 (BB；5.61 ± 0.56 mg C m-3)、及異營性細菌生產力 (BP；1.01 ± 0.12 mg C m-3 d-1)均較「沙塵暴前」有明顯提升的現象，其中異營性細菌生物量更在「沙塵暴後」時期達至相對高值 (5.93 mg C m-3)。進一步分析顯示黑潮海域植浮群聚可能受到沙塵暴帶來的微量金屬元素的刺激而促進其生長，此推測可由大氣所沉降的溶解性鐵元素濃度 (Fe-soluble)分別與PP (r = 0.94, p < 0.05)及浮游植物置換率 (Pμ) (r = 0.90, p < 0.05)之間有著顯著正相關得到佐證。此外，分析結果也顯示研究期間溶解態有機碳 (DOC)對Chl-a及BB積分平均值之間有一顯著關係式存在：IDOCavg = 1762.4 × IChl-aavg - 487.3 × IBBavg + 3302 (r2 = 0.94, p < 0.01)；此關係式建議在浮游植物大量生長的同時，水體中溶解態有機碳的濃度會隨浮游植物量的變化而改變，而此大量供應的基質(例如：溶解態有機碳)則會受到異營性細菌的利用。而初級生產力 (PP)與群聚呼吸率 (CR)之比值 (P/R ratio)為0.45 ± 0.40，據此研判研究期間，本海域是屬於異營性生態系，但值得注意的是「沙塵暴中」時期表層水體 (25 m以淺)的P/R ratio約為2左右，顯示此時水體中自營作用旺盛，浮游植物行光合作用所生合成的有機碳量足夠提供整體浮游生物群聚消耗，並可能有多餘的有機碳輸出。

關鍵字

亞洲沙塵暴 ； 黑潮 ； 有機碳循環 ； 無機營養鹽 ； 初級生產力

並列摘要

The purpose of this study is to investigate how the Asian dust storm (AD) affects organic carbon cycling in the Kuroshio Water. Samples were collected from a station (123° 10’ °E ; 25° 5’ °N) located in the Kuroshio, northeastern of Taiwan during the AD season in March, 2006. To compare, the AD event is defined as aerosol [Al] >3000 ng m-3, and the pre-AD and the after-AD periods refer to 3 days prior to and after the AD event, respectively. Results showed that the biogeochemical parameters, including nitrate (NO3- ; 0.16 ± 0.04 μM), chlorophyll a (Chl-a; 0.50 ± 0.16 mg Chl m-3), primary production (PP；9.95 ± 4.73 mg C m-3 d-1), biomass (BB; 5.61 ± 0.56 mg C m-3) and production (BP; 1.01 ± 0.12 mg C m-3 d-1) of heterotrophic bacteria increased significantly in the AD period compared to the pre-AD period. Even more, the BB reached maximum (5.93 mg C m-3) in the after-AD period. Further analyses suggest that growth of phytoplankton has been stimulated by iron elements from aerosol deposited during the AD period. This assumption can be supported by the significant relationships observed between PP and water-soluble iron concentration (r = 0.94, p < 0.05) and between phytoplankton turnover rate (Pμ) and Fe-soluble (r = 0.90, p < 0.05). In addition, a significant relationship was evident among the average values of dissolved organic carbon (DOC), Chl-a, and BB, and it can be expressed as following, IDOCavg = 1762.4 × IChl-aavg - 487.3 × IBBavg + 3302 (r2 = 0.94, p < 0.01). This result suggests that DOC concentration increased with growth of phytoplankton. In turn, the abundant DOC served as substrate for heterotrophic bacteria. As the P/R ratio, the mean ± SD value was 0.45 ± 0.40, and it suggests that the Kuroshio Water ecosystem was heterotrophic. Notably, the P/R ratio was larger than 2 in the surface water (< 25 m) during the AD period. It indicates that organic carbon produced by robust growth of phytoplankton in the surface water was more than sufficient for the consumption of plankton communities, and it can be expected that there was residual organic carbon exported into other systems.

並列關鍵字

Asian dust storm ； Kuroshio Current ； organic carbon cycling ； inorganic nutrients ； primary production

參考文獻

賴昭成 (2004) 亞熱帶沿岸海域細菌呼吸率與群聚呼吸率之季節變化研究。國立臺灣大學海洋研究所碩士論文

白書禎 郭近瑜 鍾仕偉 蘇宗德 (1998) 疊氮修正希巴辣光度測氧法及其在環境監測上的應用。Journal of the Chinese Chemical Society, 56(3)：173-185.

苗佑軍 (2007) 南灣珊瑚礁海域浮游生物群聚呼吸率及有機碳循環之研究。國立臺灣師範大學生命科學所碩士論文

柯銘澤 (2001) 臺灣周圍的流場。國立臺灣大學海洋研究所碩士論文

Duce R. A., Liss P. S., Merrill J. T., Atlas E. L., Buat-Menard P., Hicks B. B., Miller J. M., Prospero J. M., Arimoto R., Church T. M., Ellis W., Galloway J. N., Hansen L., Jickells T. D., Knap A. H., Reinhardt K. H., Schneider B., Soudine A., Tokos J. J., Tsunogai S., Wollast R., Zhou M. (1991) The atmospheric input of trace species to the world ocean. Global Biogeochemical Cycles, 5：193-259.