海洋初级生产过程是海洋碳循环的重要组成部分,影响生物地球化学循环和全球气候变化。浮游植物作为海洋初级生产的主要贡献者,按粒径大小可分为小型(micro粒级,>20μm)、微型(nano粒级,2~20μm)和微微型(pico粒级,<2μm)。不同粒...海洋初级生产过程是海洋碳循环的重要组成部分,影响生物地球化学循环和全球气候变化。浮游植物作为海洋初级生产的主要贡献者,按粒径大小可分为小型(micro粒级,>20μm)、微型(nano粒级,2~20μm)和微微型(pico粒级,<2μm)。不同粒级浮游植物初级生产力(size-fractionated primary production,PP_(size))对总初级生产力贡献不同,在海洋物质能量流动及碳循环中扮演着不同角色。本文基于2019年南海西部夏季航次12个站位的生物光学剖面数据,研究了南海西部分粒级浮游植物叶绿素a浓度和初级生产力的空间分布及它们对总叶绿素a浓度和总初级生产力的贡献百分比。利用各粒级670nm波段的浮游植物吸收系数[size-fractionated phytoplankton absorption coefficient at 670nm,a_(ph-size)(670)]与光合有效辐射(photosynthetically active radiation,PAR)的乘积[a_(ph-size)(670)×PAR]建立了南海分粒级初级生产力算法,对于小型、微型和微微型浮游植物数据集,log[a_(ph-size)(670)×PAR]与log(PP_(size))之间的决定系数R^(2)分别为0.64、0.76和0.67。交叉验证的结果表明,该算法具有良好的泛化性能。其性能显著优于仅利用浮游植物吸收系数估算分粒级初级生产力的算法,表明PAR是影响分粒级初级生产力变化的重要因素之一。采用基于叶绿素a浓度的算法估算各粒级初级生产力时,针对小型和微微型浮游植物数据集,该算法的性能与本文构建的算法近似;但针对微型浮游植物数据集时,基于叶绿素a浓度的算法性能显著较低,这可能归因于微型浮游植物吸收系数与叶绿素a浓度间的弱相关性。展开更多
To investigate the dynamics of phytoplankton size structure in the Pearl River estuary, concentrations of size-fractionated chlorophyll a (Chl a) were determined during four cruises carried out in 2008 and 2010. The d...To investigate the dynamics of phytoplankton size structure in the Pearl River estuary, concentrations of size-fractionated chlorophyll a (Chl a) were determined during four cruises carried out in 2008 and 2010. The distribution of Chl a in this geographical location showed a high degree of temporal variation. Chl a concentrations were highest in autumn, approximately three times higher than those in summer and winter. Microphytoplankton was the dominant contributor, accounting for 66.9% of the Chl a concentration in autumn 2008. In summer and spring 2008, nano-sized cells dominated the phytoplankton population throughout the study region. During the winter cruise, two different areas of water were found, characterized by (1) low salinity and high nutrient content and (2) high salinity and low nutrient content; nano- and picophytoplankton co-dominated the first area, while microphytoplankton dominated the second. It is arguable that grazing could have played a role in determining phytoplankton community size structure in winter. Nutrient concentrations were assumed not to limit phytoplankton growth during the investigation period. Size-differential capacity in competing for the resources available under different hydrodynamic conditions seemed to be the major factor in determining seasonal variation in the structure of the phytoplankton communities. High N:P ratios in the Pearl River estuary had major implications for nutrient pollution control. Our results indicated that studies of phytoplankton size structure provide greater insight into phytoplankton dynamics and are necessary to better manage water quality in the Pearl River estuary.展开更多
文摘海洋初级生产过程是海洋碳循环的重要组成部分,影响生物地球化学循环和全球气候变化。浮游植物作为海洋初级生产的主要贡献者,按粒径大小可分为小型(micro粒级,>20μm)、微型(nano粒级,2~20μm)和微微型(pico粒级,<2μm)。不同粒级浮游植物初级生产力(size-fractionated primary production,PP_(size))对总初级生产力贡献不同,在海洋物质能量流动及碳循环中扮演着不同角色。本文基于2019年南海西部夏季航次12个站位的生物光学剖面数据,研究了南海西部分粒级浮游植物叶绿素a浓度和初级生产力的空间分布及它们对总叶绿素a浓度和总初级生产力的贡献百分比。利用各粒级670nm波段的浮游植物吸收系数[size-fractionated phytoplankton absorption coefficient at 670nm,a_(ph-size)(670)]与光合有效辐射(photosynthetically active radiation,PAR)的乘积[a_(ph-size)(670)×PAR]建立了南海分粒级初级生产力算法,对于小型、微型和微微型浮游植物数据集,log[a_(ph-size)(670)×PAR]与log(PP_(size))之间的决定系数R^(2)分别为0.64、0.76和0.67。交叉验证的结果表明,该算法具有良好的泛化性能。其性能显著优于仅利用浮游植物吸收系数估算分粒级初级生产力的算法,表明PAR是影响分粒级初级生产力变化的重要因素之一。采用基于叶绿素a浓度的算法估算各粒级初级生产力时,针对小型和微微型浮游植物数据集,该算法的性能与本文构建的算法近似;但针对微型浮游植物数据集时,基于叶绿素a浓度的算法性能显著较低,这可能归因于微型浮游植物吸收系数与叶绿素a浓度间的弱相关性。
基金supported by the National Basic Research Program of China (2010CB428702)Public Science and Technology Research Funds Projects of Ocean(201005015)National Science & Technology Pillar Program of China(2012BAC07B05)
文摘To investigate the dynamics of phytoplankton size structure in the Pearl River estuary, concentrations of size-fractionated chlorophyll a (Chl a) were determined during four cruises carried out in 2008 and 2010. The distribution of Chl a in this geographical location showed a high degree of temporal variation. Chl a concentrations were highest in autumn, approximately three times higher than those in summer and winter. Microphytoplankton was the dominant contributor, accounting for 66.9% of the Chl a concentration in autumn 2008. In summer and spring 2008, nano-sized cells dominated the phytoplankton population throughout the study region. During the winter cruise, two different areas of water were found, characterized by (1) low salinity and high nutrient content and (2) high salinity and low nutrient content; nano- and picophytoplankton co-dominated the first area, while microphytoplankton dominated the second. It is arguable that grazing could have played a role in determining phytoplankton community size structure in winter. Nutrient concentrations were assumed not to limit phytoplankton growth during the investigation period. Size-differential capacity in competing for the resources available under different hydrodynamic conditions seemed to be the major factor in determining seasonal variation in the structure of the phytoplankton communities. High N:P ratios in the Pearl River estuary had major implications for nutrient pollution control. Our results indicated that studies of phytoplankton size structure provide greater insight into phytoplankton dynamics and are necessary to better manage water quality in the Pearl River estuary.
