长江口-浙闽沿岸沉积色素的分布特征及其指示意义

Distribution Characteristics of Sedimentary Pigments in the Changjiang Estuary and Zhe-Min Coast and Its Implications

利用高效液相色谱法分析了长江口-浙闽沿岸表层沉积物中的色素组成和含量,探讨了海洋初级生产力、浮游植物功能类群和浮游植物色素保存效率的空间分布特征及其影响因素.结果表明,沉积物中的色素类型主要为沉积绿素(chloropigments,Chlorins)[包括叶绿素a(chlorophyll-a,Chl-a)及其降解产物(pheopigments,Pheo-a),如脱镁叶绿素a(pheophytin-a,PHtin-a)、脱镁叶绿酸a(pheophorbide-a,PHide-a)、焦脱镁叶绿素a(p Pheophytin-a,p PHtin-a)、甾醇绿素酯(sterol chlorin esters,SCEs)和胡萝卜醇绿素酯(carotenol chlorin esters,CCEs)].Chlorins高值区呈南北两大斑块状分布,可能主要是受到长江冲淡水及浙闽沿岸泥质区上升流输运的营养盐的影响.研究区域内类胡萝卜素整体上无明显趋势性变化,在长江口以及浙闽沿岸各呈现一个高值区.基于沉积物中特征类胡萝卜素比例估算得到的浮游植物功能类群中硅藻、甲藻、定鞭藻、青绿藻、隐藻和蓝藻的相对贡献分别为48.8%±17.4%、10.7%±11.5%、8.1%±7.2%、18.6%±8.2%、9.4%±6.4%和4.3%±3.2%.对营养盐水平、水体盐度等外界环境的偏好导致硅藻和甲藻比例离岸降低,青绿藻、隐藻和蓝藻比例离岸增加.Chl-a/Pheo-a比值的分布表明,较高的沉积速率以及季节性的底层水体缺氧事件导致了近岸海域(长江口最大浑浊带外缘、杭州湾湾口以及浙闽沿岸上升流区)具有较高的沉积色素保存效率,这些沉积色素保存效率较高的区域可能是进行海洋生态环境历史重建的理想区域,而杭州湾水体通过舟山群岛与外部海水进行水体交换时造成的较差沉积环境可能是导致杭州湾外海具有较低沉积色素含量和较低保存效率的主要原因.

Compositions and contents of sedimentary pigments were examined using high performance liquid chromatography in order to discuss the spatial distributions of phytoplankton primary production,phytoplankton functional type and the preservation efficiency of phytoplankton pigments and their influencing factors. The results showed that: chloropigments [Chlorins,including chlorophyll-a( Chla) and pheopigments( Pheo-a),such as pheophytin-a( PHtin-a),pheophorbide-a( PHide-a),p Pheophytin-a( p PHtin-a),sterol chlorin esters( SCEs) and carotenol chlorin esters( CCEs) ] were the major type of sedimentary pigments. The nutrients inputs from Changjiang Diluted Water and upwelling in the Zhe-Min coastal mud area were the major cause for the patchy distribution with high sedimentary chloropigment contents. Carotenoid contents showed no trending changes and exhibited high values in the Changjiang Estuary and Zhe-Min Coasts. Based on the relative proportions of each diagnostic carotenoid to the total diagnostic carotenoids in the sediments,the relative contributions of diatoms,dinoflagellates,prymnesiophytes,prasinophytes,cryptophytes and cyanobacterias in the phytoplankton fuctional types were 48. 8% ± 17. 4%,10. 7% ± 11. 5%,8. 1% ± 7. 2%,18. 6% ± 8. 2%,9. 4% ± 6. 4% and4. 3% ± 3. 2%,respectively. The preference for external environmental conditions( e. g. nutrient level and water salinity) was the main cause for the decreasing trends of diatoms and dinoflagellates proportions and the increasing trends of prasinophytes,cryptophytes and cyanobacterias seawards. Based on the spatial distribution of Chl-a / Pheo-a ratios, the higher preservation efficiencies of sedimentary pigments in the coastal regions( e. g. outer edge of maximum turbidity zone in the Changjiang Estuary,mouth of the Hangzhou Bay and upwelling region in the Zhe-Min Coast) were mainly due to the higher sedimentation rate and seasonal occurrences of hypoxia in bottom water,and these regions with higher sedimentary pigment preservation efficiencies were probably ideal areas for themarine eco-environmental evolutions. The bad sedimentary environment caused by the water exchange inside and outside of Hangzhou Bay was the dominant reason for the low sedimentary pigment contents and preservation efficiencies in this region.