【作者】 栾青杉；

【导师】 陈雪忠； 孙军；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋生态学， 2010， 博士

【摘要】 颗石藻是海洋浮游植物功能群中一类重要的钙化生物类群,同时也是海洋中生源无机碳的主要来源,其通过光合作用(有机碳泵)和钙化作用(碳酸盐反向泵)两个过程,将海水中的溶解无机碳(DIC)转化为颗粒有机碳(POC)和颗粒无机碳(PIC)。本研究基于2009年冬季(2月11日至21日)在南海北部进行的断面调查,以及2009年夏季(7月18日至8月31日)在南海、黄东海进行的大面调查。研究内容主要包括:海水叶绿素a含量;浮游植物丰度和碳生物量;颗石藻丰度、碳生物量和颗石粒方解石(CaCO3)含量;颗粒碳库(Phyto-C、POC、PIC);钙化速率(pPIC)和固碳速率(pPOC);温度、盐度、营养盐等参数。海水叶绿素a含量使用荧光法进行测定;浮游植物丰度和碳生物量采用Uterm?hl倒置显微镜和细胞体积转化法;颗石藻丰度和碳生物量采用偏光显微镜方法;颗石粒方解石含量采用扫描电子显微镜颗石粒体积转化法;POC测定使用CHN分析仪进行;PIC测定采用电感耦合等离子体发射光谱(ICP-OES)进行;钙化速率和固碳速率采用14C微扩散法进行;温盐采用CTD实时监测;营养盐使用自动分析仪进行。对叶绿素a含量、浮游植物群落、颗石藻群落、颗石粒CaCO3、颗石藻和方解石通量进行研究后发现:2009年夏季调查期间,叶绿素a高值主要出现在海水上混合层(SML)以下,南海叶绿素a含量为0.401±0.322 mg m-3,东海0.696±0.669 m g m-3,黄海0.751±0. 525 m g m-3。南海总浮游植物丰度平均1.39×104 cells/L,高值为硅藻的柔弱伪菱形藻(Pseudo-nitzschia delicatissima)控制,东海平均7.72×103 cells/L,高值为硅藻的角毛藻(Chaetoceros spp.)控制,黄海平均8.41×103 cells/L,高值为甲藻的具齿原甲藻(Prorocentrum dentatum)控制。颗石藻优势种主要为赫氏艾密里藻(Emiliania huxleyi)和大洋桥石藻(Gephyrocapsa oceanica)。南海总颗石藻丰度为4.24±5.61×103 cells L-1(2009年冬季为40.9±37.0×103 cells L-1,是夏季的近十倍),黄东海为8.41±7.95×103 cells L-1。南海颗石粒CaCO3含量平均51.9±50.5 mg m-2,黄东海为77.2±81.4 mg m-2。南海总颗石藻现存量为286.0±273.2×106 cells m-2,黄东海为506.4±527.4×106 cells m-2。南海总颗石藻通量为9.7±9.0×106 cells m-2 d-1,黄东海为20.7±15.7×106 cells m-2 d-1。南海总方解石通量为1.80±1.70 mg m-2 d-1,黄东海为3.08±2.33 mg m-2 d-1。对颗粒碳库、钙化速率和固碳速率进行研究后发现:2009年夏季调查期间,南海浮游植物碳(Phyto-C)为24.8±30.2 mmol m-2,黄东海为83.4±112.0 mmol m-2。南海POC为382.6±139.6 mmol m-2,黄东海为431.4±136.2 mmol m-2。南海PIC为31.9±21.6 mmol m-2,黄东海为53.5±54.3 mmol m-2。南海pPIC平均6.48±3.19μmol C m-3 d-(15.43±1.77 mg C m-2 d-1),黄东海平均9.95±5.53μmol C m-3 d-1(6.17±2.75 mg C m-2 d-1)。南海pPOC平均0.402±1.457 mmol C m-3 d-1(291.7±397.1 mg C m-2 d-1),黄东海平均0.736±0.890 mmol C m-3 d-1(468.7±375.6 mg C m-2 d-1)。对基于C吸收的生长率、C库的周转、钙化对海洋C固定的贡献、雨率(pPIC:pPOC)动态进行研究后发现:2009年夏季调查期间,南海μ-PIC为0.018±0.008 d-1,黄东海为0.016±0.013 d-1。南海μ-POC为0.054±0.043 d-1,黄东海为0.093±0.074 d-1。南海μ-PhytoC为0.83±0.52 d-1,黄东海为0.63±0.51 d-1。南海τ-PIC为67.9±32.6 days,黄东海为131.1±129.9 days。南海τ-POC为31.9±26.0 days,黄东海为21.6±22.9 days。南海τ-PhytoC为1.37±1.20 days,黄东海为4.85±9.86 days。南海颗石藻钙化占到总碳固定的3.5±2.8%,黄东海占到1.9±1.5%。南海颗石藻有机碳对总有机碳固定的贡献为5.4±4.5%,黄东海为2.9±2.3%。南海雨率变化在0.002 ~ 0.412之间,平均0.067±0.078,黄东海变化在0.003 ~ 0.102之间,平均0.034±0.031。综合以上研究,夏季台湾岛东北部黑潮影响区、菲律宾吕宋海峡黑潮上游分支入侵区、东南亚时间序列站(SEATS)以及珠江口与陆架的邻接区,是今生颗石藻群落的主要分布区域。尽管E. huxleyi在总颗石藻丰度、现存量、颗石球通量上占有绝对优势,但是因其细胞体积和颗石粒体积相对较小,因此其在有机碳含量、方解石现存量、方解石通量上的贡献相对较低。相反,细孔钙盘藻(Calcidiscus leptoporus)、纤细伞球藻(Umbellosphaera tenuis)等颗石粒钙化程度高、CaCO3含量大的物种对碳的贡献也同样不可忽视。尽管黄东海的颗石藻钙化速率比起南海来有所增加,但是在黄东海,硅甲藻等光合自养生物的初级生产要比南海高很多,因此导致了南海的雨率要显著高于黄东海。同样,尽管钙化速率在垂向上的变化范围不是很大,但是固碳速率随水深增加却急速下降,因此导致了雨率随水深增加而显著升高,高值多出现在近真光层底部的水体中。比较了海洋上层生产与深层输出后发现,上层水体有机碳生产在向深层输出的过程中,再矿化(氧化作用)还是十分显著的,最后只有约0.7%的有机碳生产能够抵达海底。但是方解石的情况却有很大的不同,由于颗石藻(方解石)是最难溶的,即使到达接近海底的深度(~ 3700 m),也只有~ 42.2%的方解石溶解,约50%的颗石藻CaCO3生产埋藏进入海底表层沉积物,从而完成大气CO2向海洋内部深层的扣押过程。从深层碳输出与表层碳生产之间量上的差异来看,方解石保持在一个数量级水平上,但是有机碳却变化在1-2个数量级上。但是如果单是从碳(C)的角度来看,抵达海底的有机碳与无机碳基本持平,无机碳埋藏占到~ 54%的总C埋藏。更多还原

【Abstract】 Coccolithophores a re i mportant calcifiers i n marine phytoplankton functional groups study and meanwhile the main sources of biogenic inorganic carbon. They play critical roles in the oceanic biogeochemical carbon cycles through their organic carbon p ump (i.e. pho tosynthesis) a nd carbonate counter p ump (i.e. c alcification) processes which transform dissolved i norganic c arbon ( DIC) i nto respectively particulate organic and inorganic matter (POC and PIC).Two cruies were carried in the coastal China Seas during winter and summer 2009. T he first crusie covered then oerthern part o fS outh China S ea (SCS) including f our transects s tudy f rom 11th to 21st Feburary. The second c ruise surveyed t he SCS, East China S ea ( ECS) a nd Y ellow Sea ( YS) with r outine investigation a nd time-series studies. Parameters that measured were the s eawater chlorophyll-a concentration, phy toplankton a bundance a nd carbon bi omass, coccolithophore abundance and biomass, standing c rop of coccolith calcium carbonate, paniculate carbon materials (Phyto-C, POC and PIC), production rates of PIC and POC, temperature, salinity and nutrients etc.For chlorophyll-a determination, the f luorescent method was used. Phytoplankton taxonomic composition and cell abundance were performed by using inverted 1 ight mi croscope and the ca rbon biomass w as ca lculated f rom the c ell biovolume and the carbon-volume relationships. Coccolithophore counts and carbon biomass convertion w ere c arried by using a m icroscope w ith p olarization optics. Coccolith calicite content was estimated by measuring the coccolith volume using the Scanning Electronic Microscope and then converted t o the calcium carbonate ma ss according to t he c alcite d ensity in the c occolith. F or particulate o rganic carbon (POC) a nd particulate i norganic c arbon ( PIC), A CHN a naly ser a nd a n I nductively Coupled Plasma O pticalE mission Spectrometer ( ICP-OES) were a pplied. Calcification and photosynthesis rates w ere m easured following t he s tandard Micro-Diffusion Technique (MDT). Temperature and salinity were monitored by the Conductivity-Temperature-Depth (CTD) e quipment. Nutrients were determined in situ by using the automatic analyser.During the s ummer c ruise, hi gh c hlorophyll-a appeared primarily u nder t he Surface Mixed Layer ( SML) of the upper seawater. Averaging chlorophyll-a in the SCS was 0.401±0.322 mg m-3, and in the ECS and YS were 0.696±0.669 mg m-3 and 0.751±0.525 mg m"3 respectively. Total phytoplankton abundance in SCS was 1.39x 104 cells/L, with the diatom Pseudo-nitzschia delicatissima being the dominated species. In ECS and YS were 7.72×103 cells/L and 8.41×103 cells/Lr espectively, and the domiant species were diatom Chaetoceros spp. a nd dinoflagellate Prorocentrum dentatum. C occolithophore r epresentative species were Emiliania huxleyi and Gephyrocapsa oceanica. Total coccolithophore abundance in SCS was 4.24±5.61×103 cells L-1 (with the abundance 40.9±37.0xl03 cellsL"1 in winter nearly t en-times 1 arger t han that o f the s ummer), and i n E CS&YS w as 8.41±7.95x 103 cells L-1. Standing crop of calcium carbonate derived from the coccolith in the SCS was 51.9±50.5 mg m-2, and in ECS&YS was 77.2±81.4 mg m-2. Standing crop of coccolithophoresin SCS was 286.0±273.2×106 cells m-2, and in ECS&YS was 506. 4±527. 4×106 cells m -2. Total c occolithophore flux i n SCS w as 9.7±9.0xl06 cellsm-2 d-1, and in ECS&YS was 20.7±15.7×106 cellsm-2 d-1. Calcite flux in SCS was 1.80±1.70 mg m-2 d-1, and in ECS&YS was 3.08±2.33 mg m-2 d-1.During the summer cruise, phytoplankton carbon (Phyto-C) in the SCS was 24.8±30.2 mmol m-2, and in the ECS&YS was 83.4±112.0 mmol m-2. Seawater POC content in SCS was 382.6±139.6 mmol m-2, and in the ECS&YS was 431.4±136.2 mmol m"2. PIC concentration in SCS was 31.9±21.6 mmol m-2, and in ECS&YS was 53.5±54.3 mmol m-2. Averaging pPIC in SCS was 6.48±3.19μmol C m-3 d-1 (5.43±1.77mgCm-2d-1), and in the ECS&YS was 9.95±5.53μmol C m-3 d-1 (6.17±2.75 mg C m-2 d-1). AveragingpPOC in SCS was 0.402±1.457 mmol C m-3 d-1 (291.7±397.1 mg C m-2 d-1), and in the ECS&YS was 0.736±0.890 mmol C m-3 d-1 (468.7±375.6 mg C m-2 d-1).During the summer cruise, //-PIC in the SCS was 0.018±0.008 d-1, and in the ECS&YS was 0.016±0.013 d-1.μ-POC in the SCS was 0.054±0.043 d-1, and in the ECS&YS was 0.093±0.074 d-1.μ-PhytoC in the SCS was 0.83±0.52 d-1, and in the ECS&YS was 0.63±0.51 d-1.τ-PIC in the SCS was 67.9±32.6 days, and in the ECS&YS was 131.1±129.9 days.τ-POC in the SCS was 31.9±26.0 days, and in the ECS&YS was 21.6±22.9 days.τ-PhytoC in the SCS was 1.37±1.20 days, and in the ECS&YS was 4.85±9.86 days. The percentage of pPIC to total carbon fixtion (pPIC + pPOC)intheSCS was 3.5±2.8%, and in the ECS&YS was 1.9±1.5%. Coccolithophore c ontributiont o total phytoplankton pa rticulate o rganic carbon production i n S CS was 5.4±4. 5%, and i n the ECS&YS was 2. 9±2.3%. The rain ratios (pPIC : pPOC) in SCS varied between 0.002 and 0.412, averaging 0.067±0.078. While it spaned from 0.003 to 0.102 in the ECS&YS, averaging 0.034±0.031.From the research that mentioned above, results showed that in summer the living coccolithophores were main distributed in the Kuroshio area of the NE Taiwan Island, the Luzon Strait where the upper stream of the Kuroshio intruded into the SCS basin, the South East Asian Tim e-series Study station ( SEATS), a nd the a dj acent a rea between the Pearl River estuary and the continental shelf of northern SCS. Although E. huxleyi was predominant in many aspects including cell abundance, standing crops of coccospheres and cell flux, the relative small cell diameter and coccolith volume decided t he m arked 1 ow v alues of estimated c arbon biomass, standing s tock o f calcium ca rbonate ma ss, ca lcite flux et c. However, two h eavy-calicified c occolith species Calcidiscus leptoporus and Umbellosphaera tennis were crucial and critical for the carbon pools as well. Although there was obvious elevating trend in the calcification rates in the ECS&YS, the relative high production rates of POC in this region caused the rain ratio decreasing dramatically in contrast to the case in the SCS. The pPIC variations in the vertical profiles were little constrained. However, the sharp decline in pPOC at depth caused the marked drawdown of rain ratios along with the increasing depth and most of the higher values appeared near the bottom of the euphotic z one. When c omparing the results o f surface pr oduction w ith deep water mass f lux d escribed in the lit eratures, results sh owed that the r emineralization (oxidation) pr ocess of o rganic matter w as s ignificant. Only ~ 0.7% o f s urface organic p roduction c an reach t he s ea floor. However, the case w as d ifferent for calcite, only ~ 42.2% of surface calcite production was dissolved when exporting to depth (even ~ 3,700 m) because of its refractory nature and around a half of calcite production could finally buried in the sendiments which constituted the ocean interior sequestration oft he a tmospheric CO2. Seen from t he q uantitative discrepancies between surface carbon production and deep water carbon flux, calcite varied within one order of magnitude in contrast with the organic matter which changed in one to two orders of magnitude. But when seeing from the carbon quota allocation, there was ba lance be tween or ganic and inorganic c arbon that reached the s ea floor, with inorganic carbon accounted ~ 54% of total carbon that buried.更多还原