【作者】 张艳萍；

【导师】 杨桂朋；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2010， 博士

【摘要】 碳水化合物是海洋中溶解有机碳的主要组成部分,是海洋有机体主要的能量、存储和结构物质,在海洋碳循环和食物链循环中起着非常重要的作用。因此开展典型近海海洋环境中溶解碳水化合物的生物地球化学研究,对明确有机物的性质、来源及其迁移转化过程具有重要意义。本文以中国近海有代表性的南海、东海、黄海和受人类活动影响较大的胶州湾为研究目标,对这些海域中溶解态单糖(MCHO)和多糖(PCHO)的浓度分布、时空变化、影响因素以及对溶解有机碳(DOC)的贡献情况进行了较为系统的研究,同时对胶州湾及其邻近海域微表层中MCHO和PCHO的浓度分布及富集情况进行了考察。主要研究结果如下：1.在实验室中建立了海水中溶解MCHO和PCHO的测定方法,其检测限为2.2μM C,精密度为1.7%-8.3%,与国外同类方法相当。2.于2009年3-4月对南海东北部及其邻近海域MCHO和PCHO的分布进行了研究,结果表明南海东北部表层海水中MCHO和PCHO的浓度分别在2.5-21.9μM C和3.4-27.9μM C之间,平均浓度分别为7.0和9.5μM C,远低于世界其他近岸海域的浓度,接近于大西洋和太平洋等开阔大洋的浓度,这显然与南海海域比较低的浮游植物生物量和生产力有关。调查海域表层海水中MCHO和PCHO浓度的高值区主要集中在珠江口附近、吕宋岛西北部和东北部附近海域。PCHO与MCHO浓度的比值在0.7-2.5之间,平均值为1.4,说明PCHO是溶解碳水化合物的主要组成部分。MCHO和PCHO浓度在150 m以浅的水体中有一个高值出现,不同深度的大洋水中(500 m、1000 m或2000 m),受复杂生物化学环境的影响,MCHO和PCHO浓度也会出现高值。周日变化的研究表明,PCHO浓度在下午15：00达到最大,在夜晚最低；MCHO浓度的高值时间滞后于PCHO浓度的高值时间,印证了“部分单糖是由多糖水解而来的”这个结论。3.于2007年11月和2009年5月分别对东海、南黄海不同深度海水中溶解MCHO和PCHO进行了调查。秋季东海、南黄海表层海水中MCHO和PCHO的浓度分别在3.1-11.7μM C和4.0-17.6μM C之间,平均值分别为6.2和6.7μM C；春季MCHO和PCHO浓度变化范围较大,分别在2.6-34.1μM C和3.7-75.1μMC之间,平均值分别为11.5和21.6μM C,明显高于秋季的调查结果。秋季表层海水中MCHO和PCHO分别平均占DOC的5.1%和5.5%,春季MCHO和PCHO分别平均占DOC的6.8%和13.1%,说明MCHO和PCHO是东海、南黄海表层海水中DOC的重要组成部分。受到长江冲淡水和黑潮水的影响,表层海水中MCHO和PCHO浓度的水平分布表现出由近岸向外海递减的分布趋势,但两个季节又呈现各自一定的特点。03断面黄海冷水团中的海水具有较低的MCHO、PCHO和浮游植物生物量。05断面东南部随着高盐、寡营养盐的黑潮水对东海的入侵,C0510和C0512站位100 m以深水体中出现MCHO、PCHO和浮游植物浓度的低值区。4.利用2007年1-10月的三个航次对北黄海MCHO和PCHO的时空分布及季节变化特征进行了系统研究。北黄海表层海水中MCHO和PCHO的浓度分别在4.5-19.3μM C和0.8-27.0μM C之间,年平均浓度分别为10.8和10.1μM C。秋季海水中溶解态MCHO和PCHO分别平均占DOC的4.1%和4.8%,是北黄海表层海水中DOC的重要组成部分。北黄海表层海水中MCHO浓度冬季最高,春季次之,秋季最低；PCHO浓度春季最高,冬季次之,秋季最低。不同季节MCHO和PCHO的水平分布特征基本相同,即呈现从辽东半岛、山东半岛近岸向外海海域逐渐降低的趋势。秋季北黄海MCHO和PCHO的垂直分布表现出类似的特征,即表层浓度略高,随着深度的增大略有减小,但变化不大。这主要是北黄海水深较浅,30 m以上水体垂直分布较为均匀,下层冷水区域内有机物沉降分解等过程对碳水化合物浓度有一定的补充作用所致。5.利用2007年8月-2008年4月的四个航次对胶州湾表层海水中MCHO和PCHO的时空分布及季节变化特征进行了研究,结果表明全年胶州湾表层海水中MCHO和PCHO的浓度分别在1.7-65.9μM C和0.3-210.2μM C之间,年平均浓度分别为13.2和21.0μM C。溶解态MCHO和PCHO全年分别平均占DOC的4.5%和7.4%,是胶州湾表层海水中DOC的重要组成部分。不同季节MCHO和PCHO的浓度变化范围较大,水平分布也略有差异,但其高值区大都集中在胶州湾东部和西部近岸海域,呈现出由近岸向湾中部递减的趋势,这主要是受到青岛市及周边地区工农业生产的迅速发展、大量工农业生产废水和居民生活污水的排入、湾内西部和东北部水域水产养殖业的发展以及胶州湾南北往复式的潮流体系的影响。胶州湾表层海水中MCHO和PCHO浓度呈现出明显的季节变化,冬季最高,秋夏季次之,春季最低,冬季MCHO和PCHO平均浓度值分别是春季平均值的2.6和4.4倍。胶州湾表层海水中PCHO/MCHO和PCHO/DOC也呈现出明显的季节变化,分别在冬季和夏季出现两个高峰,与浮游植物生物量的双峰型季节变化趋势一致。MCHO能够直接被异养细菌吸收利用,迅速参与新陈代谢过程,具有较强生物活性,所以MCHO/DOC的月平均变化范围较小,季节变化不明显。线性回归结果表明,夏、春季航次中,表层海水中总溶解碳水化合物浓度和盐度具有显著的线性负相关性,进一步说明了河流输入对胶州湾内碳水化合物浓度分布的重要影响。6.于2008年7月和11月分别对胶州湾及其邻近海域微表层与表层海水中MCHO和PCHO的浓度分布及富集情况进行了研究。夏季胶州湾微表层海水中MCHO和PCHO浓度分别为22.5(4.7-54.7)和24.3(8.3-48.6)μM C,秋季胶州湾及其邻近海域微表层海水中的浓度分别为15.3(7.5-42.5)和20.8(11.3-36.6)μM C。因此,微表层海水中MCHO和PCHO浓度呈现出一定的季节变化,夏季高于秋季,这可能是受到夏季胶州湾及其邻近海域浒苔大规模爆发的影响。夏季MCHO和PCHO在微表层的平均富集因子分别为1.3和1.4,秋季平均富集因子分别为1.9和1.6,表明MCHO和PCHO在微表层中都得到一定程度的富集,而且夏季的富集程度低于秋季,这与碳水化合物本身的物理化学性质、水体性质以及海区海况等环境条件密切相关。线性回归分析表明,微表层中MCHO、PCHO和DOC与它们在表层中的浓度显著相关,说明微表层与表层水体间具有频繁、强烈的交换作用。表层海水中总溶解碳水化合物和盐度具有显著的线性负相关性,充分说明了河流输入和水团混合过程对胶州湾及其邻近海域内碳水化合物浓度的重要影响。更多还原

【Abstract】 Carbohydrates are the largest identified fraction of dissolved organic carbon in the ocean, and they serve as energy, storage, and structural components in marine organisms, which play important roles in the marine carbon cycle and marine food web cycle. Therefore studies on the biogeochemistry of dissolved carbohydrates in representative coastal waters will be helpful for realizing the characteristics, sources and degradation pathways of the organic matter.In the present dissertation, distributions, influencing factors of dissolved monosaccharides (MCHO) and polysaccharides (PCHO), and their contributions to dissolved organic carbon (DOC) in the coastal waters of China, i.e. the South China Sea, the East China Sea, the Yellow Sea and the Jiaozhou Bay, were systematically studied for the first time. Furthermore, the distributions and enrichment factors of MCHO and PCHO in the surface microlayer water of the Jiaozhou Bay and its adjacent area were detailedly investigated. The main conclusions are drawn as follows:1. The spectrophotometric method has been developed in our lab for the determination of dissolved MCHO and PCHO in seawater based on the references. The detection limit is 2.2μM C and the precision varies from 1.7% to 8.3%.2. The concentrations of MCHO and PCHO were determined in the northeastern South China Sea from March to April 2009. In the surface water, average concentrations of MCHO and PCHO were 7.0 and 9.5μM C, respectively. We found that these values in the study area were much lower than the values obtained from the other coastal and estuarine locations. On the other hand, our data were consistent with those of the Atlantic and Pacific Ocean water, which was attributed to the low phytoplankton biomass and primary production in this area. Higher concentrations of MCHO and PCHO occurred in the Zhujiang delta region, the northwest and northeast regions of the Luzon Island. The ratios of PCHO to MCHO ranged from 0.7 to 2.5 with an average of 1.4, suggesting that the polymeric compounds were much more abundant in total dissolved carbohydrates. Higher concentrations of MCHO and PCHO were observed in the water less than a depth of 150 m for vertical profiles. Higher values were also found in the deeper water (500 m,1000 m, or 2000 m depth). The concentrations of PCHO showed a diurnal variation at an anchor station with the highest value at 15:00 and lowest value at night. The maximum concentration of MCHO appeared at 18:00, which was later than that of PCHO. This observation further supported the hypothesis that MCHO was derived, in part, from the hydrolysis of PCHO.3. The horizontal and vertical distributions of MCHO and PCHO were examined in the East China Sea and the South Yellow Sea in November 2007 and May 2009, respectively. The concentrations of MCHO and PCHO in the surface water ranged from 3.1 to 11.7μM C and from 4.0 to 17.6μM C in autumn, respectively, with average values of 6.2 and 6.7μM C. In contrast, the average values of MCHO and PCHO in spring were 11.5 and 21.6μM C, respectively, which were higher than those in autumn. On average, MCHO and PCHO accounted for 5.1% and 5.5% of DOC in autumn, respectively, while MCHO and PCHO accounted for 6.8% and 13.1% of DOC in spring. This result indicated that dissolved carbohydrates were an important constituent of DOC in the surface seawater of the East China Sea and the South Yellow Sea. The horizontal distributions of MCHO and PCHO were obviously influenced by the Yangtze River effluent and the oligotrophic Kuroshio waters, decreasing from inshore to offshore sites. At transect 03, MCHO, PCHO and phytoplankton biomass showed low values in the Yellow Sea Cold Water Mass. At the southeastern part of transect 05, the low concentrations of NCHO, PCHO and phytoplankton biomass reflected the characteristics of Kuroshio waters.4. Seasonal variations of MCHO and PCHO were investigated during three cruises in the North Yellow Sea from January to October 2007. The concentrations of MCHO and PCHO varied from 4.5 to 19.3μM C and from 0.8 to 27.0μM C in the surface water, respectively, with annual averages of 10.8 and 10.1μM C. On average, MCHO and PCHO accounted for 4.1% and 4.8% of DOC, respectively. The concentrations of MCHO showed an obvious seasonal variation with highest average value in winter and lowest value in autumn. In contrast, the maximum average concentration of PCHO was 12.8μM C in spring and the minimum value was 8.1μM C in autumn, respectively. Both MCHO and PCHO displayed a similar distribution pattern in different seasons, decreasing gradually from the shore waters of Liaodong and Shandong Peninsula to the open sea. The concentrations of MCHO and PCHO at four stations in autumn decreased gradually from the surface layer to the bottom layer. However, the difference of concentrations between the surface and bottom water was not significant. This trend was consistent with the well-mixing aquatic system between 0 and 30 m in autumn, and the supplement of dissolved carbohydrates from the bottom water by microbial hydrolysis of organic matter.5. The distributions and seasonal variations of MCHO and PCHO in the surface water of the Jiaozhou Bay were investigated during four cruises from August 2007 to April 2008. The concentrations of MCHO and PCHO ranged from 1.7 to 65.9μM C and from 0.3 to 210.2μM C for all samples, respectively, with annual averages of 13.2 and 21.0μM C. On average, MCHO and PCHO accounted for 4.5% and 7.4% of DOC, respectively. This result indicated that dissolved carbohydrates were an important constituent of DOC in the surface seawater of the Jiaozhou Bay. Although the concentrations of MCHO and PCHO varied during difference cruises, higher concentrations occurred in the east and west coast region, decreasing gradually from the coast to the central region. This pattern may be strongly influenced by the industrial and domestic waste discharges, the development of shellfish aquaculture in the western and northeastern eutrophic coast, and the tidal current which moves back and forth in the north-south direction. The concentrations of MCHO and PCHO exhibited a marked seasonal variation, with the highest values in winter and the lowest in spring. As a mean, the concentrations of MCHO and PCHO in winter are 2.2 and 4.4 times higher than those in spring, respectively. The ratios of PCHO to MCHO exhibited two peaks in winter and summer, respectively, as well as the ratios of PCHO to DOC, which fundamentally coincided with those of phytoplankton biomass in the bay. MCHO were biologically labile molecules, which could be taken up directly and metabolized quickly by heterotrophic bacteria. Chemically they would be more stable than PCHO in seawater. Thus, it was reasonable that the ratios of MCHO to DOC varied less than those of PCHO. Negative correlations between concentrations of total dissolved carbohydrates and salinity in summer and spring suggested that riverine input around the Jiaozhou Bay had an important contribution to the concentrations of dissolved carbohydrates in surface seawater.6. The properties and enrichment factors of dissolved MCHO and PCHO were studied in the sea surface microlayer and their related bulk surface water of the Jiaozhou Bay and its adjacent area in July and November,2008, respectively. The concentrations of MCHO and PCHO in the surface microlayer varied in the ranges of 4.7-54.7 and 8.3-48.6μM C in July, respectively, compared to 7.5-42.5 and 11.3-36.6μM C in November. Average concentrations in July were 22.5 and 24.3μM C for MCHO and PCHO, respectively, while those values in November were 15.3 and 20.8μM C. The values were higher in July than in November, presumably due to the remarkably high phytoplankton biomass caused by a green-tide occurred in July 2008 in the bay and its adjacent area. MCHO and PCHO exhibited an extent of enrichment in the microlayer relative to those in the surface water. The average enrichment factors of MCHO and PCHO in the surface microlayer were 1.3 and 1.4 in July, respectively. In contrast, the average enrichment factors of MCHO and PCHO in November were 1.9 and 1.6. Thus, the microlayer enrichment of MCHO and PCHO also displayed seasonal variation, with smaller value in summer, which was attributed to the carbohydrate characteristics and the physical and chemical environment. Our data also showed that the concentrations of MCHO, PCHO, and DOC in the surface microlayer were strongly correlated with those in the surface water, indicating that there was a strong exchange effect between the microlayer and the underlying water. The concentrations of total dissolved carbohydrates in the bulk surface water were closely correlated with salinity during the cruises, suggesting that riverine input and water exchange processes had an important effect on the concentrations of dissolved carbohydrates in surface seawater of the investigated area.更多还原