| 摘要: |
| 从研究胶州湾沉积物中生源硅入手,利用对比分析对其限制的原因进行了探讨。研究表明,相对于邻近的黄海和渤海沉积物,胶州湾沉积物中的生源硅含量较高,在湾内外的三个站表层沉积物中生源硅的含量分别为1.58%、1.44%、1.48%,在整个柱状样中的平均含量分别为1.54%、1.48%和1.39%,属于高生源硅含量区。沉积物中BSi∶TN远远大于1,BSi∶TP也远远大于16,与水体中Si∶TN<1,BSi∶16P<1相反,同时沉积物中的OC∶BSi值远远小于Redfield比值(106∶16),表明沉积物中有机质的分解速率远大于BSi的分解速率,生源硅分解的较慢。研究还发现,生源硅和有机碳的含量有明显的正相关关系,二者共同作用的结果是造成相当大的一部分BSi被埋藏,不能参与再循环,从而水体中的硅被永久地“清除”,造成水体硅的缺乏,这可能是造成胶州湾浮游植物生长硅限制的根本原因。湾外BSi较湾内低的主要原因是湾外的沉积物因其有机质含量低,且沉积物的颗粒粗而造成BSi的溶解速率比湾内的高。根据沉积物中生源硅的沉积通量和初级生产力的对比可推知,由硅藻形成的生源硅在沉降过程中平均只有15. %被分解重新进入水体,其余的84.5%可被埋葬而形成沉积物。而胶州湾沉积物中的硅通过沉积物-海水界面返回到水体中的速率也小于生源硅的沉积速率,这进一步证明了海水中的硅不断向沉积物迁移,导致水体中硅含量持续的低水平,进而使Si成为浮游植物生长限制因子的主要原因。 |
| 关键词: 生源硅 限制因子 胶州湾沉积物 |
| DOI： |
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| 基金项目:中国科学院创新工程重要方向性项目,KZCX3-SW-214号;青岛市科技将才专项计划,04-3-JJ-03号;中国科学院“百人计划”项目,科人2003-202号;中国科学院创新重大项目,KZCX1-SW-01-08号 |
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| HIGH CONTENTS OF BIOGENIC SILICATE IN JIAOZHOU BAY SEDIMENTS——EVIDENCE OF SI-LIMITATION TO PHYTOPLANKTON PRIMARY PRODUCTION |
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LI Xue-Gang1, SONG Jin-Ming1, YUAN Hua-Mao1,2, LI Feng-Ye1, SUN Song1
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1.Key Lab of Marine Ecology & Environmental Sciences,Institute of Oceanology,Chinese Academy of Sciences,Qingdao,266071;2.Graduate School,Chinese Academy of Sciences,Beijing,100039
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| Abstract: |
| Silicate is an essential chemical requirement for certain biota such as diatoms, radiolarian, silicoflagellates and siliceous sponges. Its abundance in seawater strongly influences the growth of diatoms. It has been widely recognized that low silicate content in seawater is a main limiting factor to phytoplankton primary production in Jiaozhou Bay. However the reason of Si-limitation remains poorly understood. In the present study we believed that the biogenic silicate content in sediment was the reason based on the analysis of field samples. The measurements have showed that the biogenic silicate content in surface sediments of the bay varied at 1.58%, 1.44% and 1.48% in the inner bay, bay mouth, and the outer bay, respectively; and the content in surface sediment was higher than it in sub-surface layer, which indicated the accumulation rate in recent years is higher than early years. The average value of the whole column samples was 1.54% in inner bay, 1.48% in bay mouth and 1.39% in outer bay. These values are obviously much higher than those in the Yellow Sea and the Bohai Sea. Thus the sediment of the Jiaozhou Bay is characterized by a high content of biogenic silicate.
The ratios between Si and C, N, P may reflect the accumulation of silicate in sediment. The ratio of Si:N:P in diatom is 16:16:1. If all of Si, N and P in sediment came from diatom that the ratio of Si:N:P in sediment would be close to 16:16:1. If the ratio is higher than 16:16:1, silicate accumulation in sediment is indicated. The BSi:TN ratios and the BSi:16P ratios in sediment were>1 but were<1 in seawater. On the other hand, the values of OC:BSi ratios in sediment were lower than these of Redfield ratio (106:16). All these data above indicated silicate has accumulated in sediment as the decomposition rate of OC is much higher than that for BSi decomposition rate in similar conditions. Close and positive correlation between OC and BSi contents was also found, which proved that biogenic silicate came form diatom. Since the BSi decomposition rate is slow, the majority of the biogenic silicate was buried and thus did not participate in silicate recycling. This fact may become the key reason for limiting phytoplankton growth in the Jiaozhou Bay. Comparing the flux of biogenic silicate from sediments with primary production rate, it can be concluded that only 15.5% of biogenic silicate was hydrolyzed when they sank down from surface to bottom in seawater, thus approx. 84.5% of biogenic silicate could reached the bottom. In other words, the majority of silicate cannot be decomposed before they deposited at bottom as the bay has such shallow depth. On the other hand, the silicate release rate from the sediment to seawater was considerably lower than that of sedimentation of biogenic silicate. Thus, in Jiaozhou Bay the silicate flux from seawater to the sediment controls the flux in opposite direction. This may be the main reason of constant silicate content low, making silicate as a limiting factor to phytoplankton primary production in the Jiaozhou Bay. In a word, the silicate accumulation in sediment is the key reason of silicate limiting to phytoplankton growth in the Jiaozhou Bay. |
| Key words: Biogenic silicate, Limiting factor, Jiaozhou Bay |
