Journal of Marine Sciences >

2023 , Vol. 41 >Issue 4: 1 - 11

DOI: https://doi.org/10.3969/j.issn.1001-909X.2023.04.001

The seasonal blooming characteristics of phytoplankton and POC export flux in the waters around South Georgia Island: Based on BGC-Argo and satellite remote sensing observations

  • ZHAO Yueran , 1 ,
  • FAN Gaojing 2 ,
  • WU Jiaqi 1, 3 ,
  • SUN Weiping 1 ,
  • PAN Jianming 1 ,
  • HAN Zhengbing , 1, *
Expand
  • 1. Key Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, MNR, Hangzhou 310012, China
  • 2. Polar Research Institute of China, Shanghai 201209, China
  • 3. Ocean College, Zhejiang University, Zhoushan 316000, China

Received date: 2023-03-01

  Revised date: 2023-05-05

  Online published: 2024-01-30

Fold

Abstract

The waters surrounding South Georgia Island are one of the highest primary productivity regions in the Southern Ocean with enormous carbon sequestration potential. However, the strength of the biological pump efficiency in this area is still uncertain due to the lack of continuous upper ocean observation data.In this study, the hydrological and biogeochemical parameters obtained from the Biogeochemical Argo (BGC-Argo) floats deployed in the South Georgia Island vicinity during the period of 2017-2020 were utilized to investigate the impacts of physical processes on biogeochemical processes and to estimate the carbon export flux in the Antarctic summer. Results indicated that both upstream (northeast of the Antarctic Peninsula) and downstream (Georgia Basin) regions of South Georgia Island exhibited strong seasonal characteristics in Chl-a, with the latter area having a 4-month sustained period of phytoplankton bloom, suggesting a stable and continuous supply of iron. Using the temporal variability of the seasonal particulate organic carbon (POC) export, the summer POC export fluxes of the upstream and downstream regions were estimated to be 7.12±3.90 mmol·m-2·d-1 and 45.29±5.40 mmol·m-2·d-1, respectively, indicating that the difference might be due to enhanced downward export of organic carbon after the deepening of the mixed layer. The study found that the region maintained a high biological pump efficiency, contrary to the previous conclusion that the Georgia Basin had “high productivity low export efficiency”, which might have been caused by the limited “real-time” representation of the entire seasonal characteristics during ship-based surveys. BGC-Argo provides high spatiotemporal resolution of multi-parameter observation data, and this study demonstrates that it can more accurately quantify and evaluate marine biogeochemical processes and carbon sequestration potential.

Key words： Southern Ocean; South Georgia Island; BGC-Argo; POC export production; Chl-a

Cite this article

ZHAO Yueran , FAN Gaojing , WU Jiaqi , SUN Weiping , PAN Jianming , HAN Zhengbing . The seasonal blooming characteristics of phytoplankton and POC export flux in the waters around South Georgia Island: Based on BGC-Argo and satellite remote sensing observations[J]. Journal of Marine Sciences, 2023 , 41(4) : 1 -11 . DOI: 10.3969/j.issn.1001-909X.2023.04.001

0 引言

南大洋是全球最大的高营养盐低叶绿素(high-nutrient low-chlorophyll,HNLC)海区,由于其具有丰富且过剩的营养盐,被认为是全球海洋中最具潜力的碳汇区,对全球碳循环有着举足轻重的作用[1]。自“铁假说”提出以来[2],已有许多“铁加富”试验表明在南大洋HNLC海域人工施加铁肥可引起浮游植物初级生产力升高[3⇓-5],铁被认为是影响南大洋浮游植物初级生产力最为关键的限制因子。与HNLC区域形成鲜明对比,南大洋还存在着许多天然铁施肥区域,主要是由天然铁源的输入而刺激浮游植物发生季节性旺发[6⇓-8],如西南极半岛[9]、南乔治亚岛[10-11]、凯尔盖朗群岛[12-13]和克罗泽群岛[14-15]等,这些高初级生产力海域为企鹅、海豹等高营养级生物提供了关键的栖息聚集地,对维持南极生态系统的稳定至关重要。
南乔治亚岛附近海域是南大洋最大的浮游植物旺发海域之一,具有丰富的生态系统、群落组成以及巨大的碳汇潜力[16],高生产力区域主要集中在南乔治亚岛西北侧的乔治亚海盆区域。许多研究推测这种区域性特征可能主要受控于水文过程[17⇓⇓⇓-21,11]。然而,该区域浮游植物初级生产力的年际变动较大[16],且存在高生产力低输出效率(high productivity low export efficiency,HPLE)的特征[22],这些现象仍需要许多生物地球化学观测资料来作进一步研究[23⇓-25,18]。
生物地球化学剖面浮标(biogeochemical Argo float, BGC-Argo)是一种新型的原位观测装置,可提供较高时空分辨率、多参数的观测数据资料,近年来被广泛应用于海洋原位观测研究[26],以弥补船基观测和卫星遥感观测的不足。本文基于南乔治亚岛附近海域BGC-Argo的原位观测资料,结合卫星遥感观测数据,探究南乔治亚岛附近海域浮游植物的旺发过程对上层海洋碳输出通量的贡献与影响。

1 材料与方法

1.1 研究海域

南乔治亚岛(37°W,55°S)位于南大洋大西洋扇区的斯科舍海东北边界[16],在极地锋(polar front,PF)和南极绕极流南锋(southern Antarctic circumpolar current front,SACCF)之间,岛屿大陆架离岸向外延伸50~150 km,并对周围海流流向产生一定影响。南极绕极流(Antarctic circumpolar current,ACC)从南乔治亚岛大陆架的西南方向到达南乔治亚岛的南部,然后分别向西和向东北分叉成两个分支,向西的分支继续向西流动,而向东北的分支则绕过南乔治亚岛的北部,转向乔治亚海盆,沿着乔治亚海盆陡峭的轮廓线反向流动,最后恢复其向东的路线[27-28]。南乔治亚岛周围水团分布受SACCF以及岛屿径流的共同影响[21,19],岛屿西南部海域水团具有威德尔海(Weddell Sea,WS)和ACC混合水团的性质[29],岛屿东北部海域水团与南极区水(Antarctic zone water,AZW)有相似的物理特性,岛屿西北部海域水团是主要来自岛屿径流的南乔治亚大陆架水(South Georgia shelf water,SGSW)[20]。

1.2 数据来源

1.2.1 BGC-Argo浮标数据

在南大洋碳和气候观测与建模(the Southern Ocean carbon and climate observations and modeling,SOCCOM)项目中筛选出研究海区邻近的BGC-Argo浮标(编号:12545)。该浮标搭载的传感器可获取温度、盐度、叶绿素(Chl-a)、硝酸盐和颗粒有机碳(particulate organic carbon,POC)等数据,其中POC数据由光学反向散射率计算得到[30]。本研究选用高分辨率数据文件,时间范围为2017年10月至2020年2月,共82个剖面数据,深度范围选取200 m以浅,温盐深数据分辨率为2 m,生化参数分辨率分别为5 m(100 m以浅)和10 m(100~200 m),垂直剖面的采样时间间隔为10天。数据质量控制全部由SOCCOM完成(https://soccom.princeton.edu/)。
该浮标于2017年底进入研究海区,沿南设得兰群岛向东移动,至2018年5月绕经该群岛东部陆架边缘后北上,然后沿北部陆架向西运动,并于2019年1月正式进入乔治亚海盆,在海盆盘旋约6个月后离开海盆继续向东部运动。浮标的漂流轨迹几乎完全沿着南极绕极流的运动方向(图1)。为便于后续讨论,本文定义南极夏季为11月至次年3月,南极冬季为4月至10月。
图1 研究海域及BGC-Argo的移动轨迹

(图中等值线表示水深,单位:m;蓝色点表示浮标剖面站点;黑粗线和红粗线分别为南极绕极流南锋(SACCF)和极锋(PF);色标采用对数处理,颜色反映1997年至2017年南半球12月至次年2月气候态Chl-a分布,数据来自欧洲航天局GlobColour项目的多元数据融合产品,空间分辨率为25 km×25 km,时间分辨率为1个月。)

Fig.1 Study area and the movement trajectory of BGC-Argo floats

(Contour lines represent water depth, unit: m. Blue dots represent the profiling float stations. The thick black line and red line indicate the southern Antarctic circumpolar current front (SACCF) and polar front (PF), respectively. Color bar uses log transformation, and the color represents the climatological distribution of Chl-a from December to February in the southern hemisphere from 1997 to 2017. The data are from the multi-sensor merged product of the European Space Agency’s GlobColour project with a spatial resolution of 25 km × 25 km and a temporal resolution of 1 month.)

1.2.2 卫星遥感数据

与BGC-Argo匹配的卫星遥感叶绿素数据来源于欧洲航天局(European Space Agency,ESA)GlobColour项目提供的多源数据融合产品(https://hermes.acri.fr/),由水色传感器SeaWiFs、MERIS、MODIS和VIIRS融合处理得到,空间分辨率为25 km×25 km,时间分辨率为8天,时间范围为2017年11月—2020年2月。

1.3 数据处理

1.3.1 硝酸盐季节性消耗与POC输出通量

根据BUESSELER[31]的定义,本研究选取100 m深度作为上层POC向下输出的界面,并利用硝酸盐的亏损法来估算碳输出通量[32]。本研究将硝酸盐标准化至盐度35[33],以减少物理过程对硝酸盐变化的影响。浮游植物光合作用所消耗的营养盐被认为是上层100 m硝酸盐的季节性消耗值,即硝酸盐的冬季储量与水体中剩余硝酸盐的浓度之差:
UN=cN(100)×100- ∫ 0 100cN(z)dz
式中:UN代表硝酸盐的季节性消耗值,z表示深度,cN(z)表示深度为z处的硝酸盐浓度,cN(100)代表100 m深度处冬季硝酸盐的浓度。
表1 基于BGC-Argo的夏季平均混合层深度、POC储量、NCP和POC输出通量

Tab.1 Summer mean values of MLD, POC storage, NCP, and POC export flux based on BGC-Argo

年份 位置 混合层深度/m POC储量/(mmol·m-2) NCP/(mmol·m-2) POC输出通量/(mmol·m-2·d-1)
2017/2018 南极半岛东北部海域 38.49±18.93 610.32±124.83 3 976.14±124.53 7.12±3.90
2018/2019 乔治亚海盆 62.40±24.55 691.62±158.92 4 591.86±316.12 45.29±5.40
南乔治亚岛所处的南大西洋浮游植物中C/N的摩尔比取7.5[34-35],据此可计算100 m以上浮游植物的净群落生产力(net community productivity,NCP):
NCP=7.5×UN
因为溶解有机碳(dissolved organic carbon,DOC)在该海域对POC输出通量贡献较低(1%~10%)[22],本研究未考虑DOC向下输出对NCP的影响。
因此,夏季POC输出量可由夏季净NCP与POC储量之差估算得到,输出通量则由POC输出量的时间变率估算得到:
k= ∑ T i × E i - n × T ¯ × E ¯ ∑ T i 2 - n × T ¯ 2
式中:k表示输出通量,n为剖面数,i代表某个剖面,Ti为某个剖面日期(以儒略日计),Ei为某个剖面POC输出量, T -和 E -分别表示整个夏季的儒略日和POC输出量平均值。

1.3.2 卫星遥感数据与BGC-Argo数据匹配

基于BGC-Argo各站点所对应日期,筛选出时间尺度上最接近的卫星遥感Chl-a数据,再对BGA-Argo站点实际距离最近像素点进行匹配。

1.3.3 混合层深度计算

混合层深度(mixed layer depth,MLD)基于BGC-Argo中的剖面观测数据,通过取距离海表10 m处的密度变化阈值0.03 kg/m3计算得到[36]。

2 结果

2.1 生化参数的时空分布

南乔治亚岛附近上层海水温度总体呈现夏高冬低的分布趋势(图2a)。2018年5月至10月期间,浮标位于南乔治亚岛南部,海表温度低于0 ℃;2018年12月,浮标进入南乔治亚岛东南部海域,海水温度开始升高,约为4 ℃左右;随着季节演替,海水温度在2019年9月最终降低至1 ℃左右。上层海水密度和盐度随季节的分布变化趋势则与温度相反(图2b,2c)。整体上,在南极夏季,南乔治亚岛附近海域的海水层化现象显著。
图2 BGC-Argo浮标获取的各生化参数剖面变化

(图中白色虚线表示混合层深度。)

Fig.2 Profiles of biogeochemical parameters of BGC-Argo floats

(The white dashed line represents the depth of the mixed layer.)

南乔治亚岛附近海域上层Chl-a质量浓度和POC浓度呈现出显著的季节性差异,即夏季高冬季低,其高值和骤变区域与地理位置有密切联系。2017年12月浮标位于南乔治亚岛与南设得兰群岛之间的南极半岛东北部海域,此时Chl-a质量浓度开始升高,到2018年2月达到全年最大值,于3月之后迅速衰减。2018年12月浮标进入南乔治亚岛东南海域,此时Chl-a质量浓度开始升高,2019年1月浮标进入乔治亚海盆,随后Chl-a质量浓度在2月达到最大值。当浮标位于乔治亚海盆内时,Chl-a质量浓度一直维持着相对较高的水平,直到2019年3月混合层深至75 m,Chl-a呈现出向下扩散的趋势,尽管Chl-a质量浓度有所降低,整个混合层的Chl-a储量却似乎有所增加(图2d)。
南乔治亚岛附近海域上层POC浓度的时空变化及分布趋势与Chl-a几乎完全相同,略有所不同的是,2018/2019年夏季POC的浓度低于2017/2018年同期(图2e)。上层硝酸盐的时空分布特征与Chl-a和POC相反,呈夏季低冬季高的特征。与南极半岛东北部海域相比,在乔治亚海盆观测到的夏季硝酸盐浓度整体更低,且低值持续时间更长(图2f)。

2.2 卫星遥感与BGC-Argo观测的Chl-a差异

如图3所示,卫星遥感与BGC-Argo观测的Chl-a变化趋势基本一致,BGC-Argo观测的Chl-a基本无缺失值,但卫星遥感获取的Chl-a则存在大量的缺失,且主要集中在冬季。2017/2018年夏季,浮标未进入南乔治亚岛海域,混合层深度较浅,卫星遥感获取的表层Chl-a均高于BGC-Argo的观测结果。而在2018/2019年夏季,浮标开始进入南乔治亚岛海域,混合层比2017/2018年夏季时南极半岛东北部海域的略深,当卫星遥感和BGC-Argo观测的Chl-a均达到峰值时,BGC-Argo观测的表层Chl-a高于卫星遥感观测结果(图3)。比较BGC-Argo观测到的表层叶绿素(Chl-a5 m)和次表层叶绿素(Chl-a50 m)发现,当夏季混合层较浅时,表层Chl-a要明显高于次表层;而在冬季,混合层加深,表层和次表层的Chl-a水平相当,甚至部分站点次表层Chl-a要高于表层(图4)。
图3 卫星遥感和BGC-Argo获取的表层Chl-a质量浓度时间序列对比

Fig.3 Comparison of time series of Chl-a mass concentration observed by remote sensing and BGC-Argo

图4 BGC-Argo观测到5 m和50 m处Chl-a质量浓度差异的浮动柱状图

(柱形顶部和底部分别表示Chl-a5 m和Chl-a50 m,绿色柱形表示Chl-a5 m大于Chl-a50 m,橙色反之,柱长表示二者的差异。)

Fig.4 Floating bar chart of the difference in Chl-a mass concentration between 5 m and 50 m observed by BGC-Argo

(The top and bottom of the bars represent Chl-a5 m or Chl-a50 m respectively. Green bars indicate that Chl-a5 m is higher than Chl-a50 m, while orange bars indicate the opposite, and the length of the bars represents the difference.)

2.3 NCP与POC输出通量

2017/2018年夏季,浮标位于南极半岛东北部海域,混合层平均深度为38.49±18.93 m,上层100 m的POC储量和NCP都较高,平均值分别为610.32±124.83 mmol·m-2和3 976.14±124.53 mmol·m-2(表1)。NCP一直保持高值至5月骤降,而POC储量从夏季初期达到峰值后迅速下降,后逐渐升高,至3月达到最大值,再缓慢下降(图5)。
图5 南乔治亚岛附近海域上层100 m的NCP与POC储量时间序列变化

Fig.5 Time series of NCP and POC storage in the upper 100 m of the waters surrounding South Georgia Island

2018/2019年夏季,浮标开始进入乔治亚海盆,混合层平均深度加深,达到62.40±24.55 m。与上一年度相似,POC储量和NCP随季节变化开始逐渐升高,NCP在2019年1月下旬达到第一个峰值,而POC储量则在2018年12月后出现多个峰值,二者的季节性均值分别为691.62±158.92 mmol·m-2和4 591.86±316.12 mmol·m-2。
与NCP和POC储量明显不同,2018/2019年浮标位于乔治亚海盆时测得的季节性POC输出量明显高于上一年,并在5月份达到峰值。通过对POC输出量时间变率的估算,2018/2019年夏季的POC输出通量达到45.29±5.40 mmol·m-2·d-1(r=0.92,p<0.05),而2017/2018年夏季仅为7.12±3.90 mmol·m-2·d-1(r=0.45,p<0.05)(图6)。尽管两个海域的Chl-a、POC储量和NCP的季节性均值相差不多,但乔治亚海盆较高的POC输出通量反映出该海域更强的碳泵效率,可能有诸多因素驱动上层POC快速且稳定地向下输出。
图6 南乔治亚岛附近海域POC输出量时间序列变化

(阴影部分表示2017/2018年和2018/2019年夏季;趋势线分别为两个夏季POC输出量相对时间的变化趋势。)

Fig.6 Time series of POC export in the waters near South Georgia Island

(The shaded area represents the summer seasons of 2017/2018 and 2018/2019; the trend line shows the temporal variation of POC export)

3 讨论

3.1 卫星遥感与BGC-Argo观测的Chl-a差异分析

由于南大洋高纬度海域易受太阳高度角和云层覆盖等影响,导致大部分卫星遥感观测数据缺失,但前人研究表明,在Chl-a质量浓度较低的南大洋开阔海域,走航与卫星遥感观测所分别获取的Chl-a质量浓度数据之间具有很好的相关性[37-38]。为探究卫星遥感观测的Chl-a和BGC-Argo观测结果之间的差异,将两种手段获取的表层Chl-a结果进行对比,剔除空白值后的卫星遥感观测值与BGC-Argo观测值的相关性显著(r=0.72,p<0.05)。当混合层深度较浅时(如在南极半岛东北部海域),卫星遥感观测到的Chl-a要略高于BGC-Argo观测到的数据;而当混合层深度较深时(如乔治亚海盆),二者基本一致或卫星遥感观测的Chl-a略低(图3)。斯科舍海[39]和南乔治亚岛附近海域[40]的走航调查中均发现相似的结果,卫星遥感观测结果略微低估了高生产力时的Chl-a,而略微高估了低生产力时的Chl-a。
导致“低估”的原因很可能是在于观测手段的时空尺度差异。卫星遥感仅能探测海洋上层几十米的Chl-a,并且易受云层等影响,而BGC-Argo却能获取整个水柱中高分辨率的Chl-a水平,这种差异是导致观测结果不一致的主要原因。尽管KORB 等[40]发现南乔治亚岛附近表层海水Chl-a质量浓度与混合层Chl-a平均质量浓度有良好的相关性,由于乔治亚海盆处混合层深度通常为50~150 m,基于BGC-Argo的数据能更为准确地反映该海域Chl-a的时空分布特征,进一步反映该地区的初级生产力水平。

3.2 乔治亚海盆区夏季浮游植物的旺发机制

前人针对乔治亚海盆区浮游植物季节性旺发现象已开展了大量的调查与研究[16⇓⇓⇓⇓-21,11,25],本文通过卫星遥感和BGC-Argo两种观测手段均发现乔治亚海盆在夏季出现大量水华,说明该海域存在生物可利用铁的维持或补给机制[41]。有研究表明,南乔治亚岛以北的浮游植物水华现象,主要是源于岛屿附近大陆架的沉积铁的补充。大陆架表层水体中溶解态铁的浓度范围为1.5~6 nmol·L-1,并由向北的羽状流水平输送至海盆区域[42-43]。乔治亚海盆表层水体中溶解态铁的浓度范围为0.5~2 nmol·L-1,基本不存在铁限制的影响,此外,岛屿下游特有的表面环流模式也与浮游植物爆发的分布特征相近[19]。
最近的研究发现2017年11月—12月期间乔治亚海盆区的溶解态铁浓度低于0.2 nmol·L-1,已处于铁限制的状态,而颗粒态铁和有机碳在水柱中存在着解耦现象,浮游植物持续水华所需的铁可能主要来自于水柱中颗粒态铁的再循环[25]。混合层深度较深可能有助于真光层底部溶解态铁重新补给到上层,这可能是乔治亚海盆出现多个Chl-a峰值的原因。南大洋的Chl-a出现双峰或多峰的现象并非乔治亚海盆独有,在南大洋的其他海域也有许多报道,如澳大利亚南部亚南极带区域的双峰现象[44]和凯尔盖朗群岛附近海域的双峰现象[45]。本研究中乔治亚海盆的Chl-a呈现出多个峰值,主要集中在12月、1月和2月,甚至在3月和4月还出现了峰值(图3),这种情况则可能是由铁的供应方式转变造成。此外,硅藻的大量繁殖造成硅酸盐的耗尽,也可能是造成这种多峰现象的原因[16]之一。

3.3 乔治亚海盆区的高POC输出通量

通过比较上、下游的夏季POC储量和NCP,发现二者均未表现出显著差异(单因素ANOVA检验,p>0.05),而混合层深度则差异显著(单因素ANOVA检验,p=0.006)。近年来,已有许多研究发现季节性混合层碳泵对海洋生物泵贡献巨大[46-47],也有研究发现乔治亚海盆区的反气旋涡与该处的高生产力有关系[48]。由于乔治亚海盆区夏季混合层平均深度明显深于南极半岛东北部海域(表1),且POC输出量的增长趋势随着时间变化相对稳定(r=0.92,图6),反映了乔治亚海盆上层POC具有持续向下层输出的机制,可能与混合层碳泵有着密切关系。海盆区水柱中颗粒态铁比有机碳具有更快的再循环效率[25],进一步表明了上层水体的混合有利于铁的循环补充和碳的向下输出。MOIGNE 等[22]通过234Th∶238U不平衡法估算了乔治亚海盆2013年1月下旬100 m水深处的输出碳通量约为22 mmol·m-2·d-1[22],略低于本文估算的结果,但该研究通过对比南乔治亚岛上、下游的输出通量和输出效率,认为乔治亚海盆具有HPLE的特征,表层高细菌活性和低粪便输出是该区域发生HPLE的主要原因,这种解释似乎又与其他人的研究结果相悖[49-50]。
乔治亚海盆高生产力主要来自于小型浮游植物(硅藻等)的贡献[48],硅藻休眠孢子被认为是上层POC向深海的高沉降通量的主要因素[24],与南大洋克罗泽群岛天然铁施肥区域的研究结果[51]相一致。最近的沉积物捕获器观测结果也显示,该海域11月和12月的水柱中碳通量主要来自于浮游动物粪便的贡献,而在1月则主要来自于硅藻休眠孢子的沉降[50]。通过沉积物捕获器的观测对比了南乔治亚岛上游(威德尔海北部)和下游(乔治亚海盆)深海的有机碳通量,也发现了乔治亚海盆区的碳通量(40.6 mmol·m-2·a-1,水深2 000 m)要高于威德尔海北部(26.4 mmol·m-2·a-1,水深1 500 m)[24]。BELCHER 等[52]在乔治亚海盆区通过沉积物捕获器获知2018年12月400 m和2 000 m水深的POC输出通量分别为3.81 mmol·m-2·d-1和3.62 mmol·m-2·d-1,据此可估算出Martin衰减系数b为0.82,低于全球均值0.86[53],表明POC向下输送具有更高的效率。这些研究均显示乔治亚海盆的生物泵运转效率较高。
GIERING 等[54]基于沉降微粒的POC含量和沉降速率,估算了2017年春末夏初时南乔治亚岛周围海域的POC输出通量为0.2~135.2 mmol·m-2·d-1,其变化范围高达4个量级,表明有机碳通量的观测存在一定偶然性。本文结果反映了整个夏季的POC输出通量受短时间尺度的物理-生物-化学过程影响较小,可以更准确地反映区域性和季节性POC输出通量。南大洋存在HPLE现象似乎是有一定的时间局限性,不足以反映整个生物泵的真实状况,尤其是在季节性更强的极地海域。因此,覆盖时间尺度更长的BGC-Argo数据,可以更为准确地评估海洋生物固碳的能力。

4 结论

本文利用南极南乔治亚岛附近海域的BGC-Argo所获取的数据资料对该海域浮游植物旺发特征进行了分析,并估算了POC输出通量,得到以下结论:1)南乔治亚岛上游(南极半岛东北部)和下游(乔治亚海盆)海域Chl-a均呈现出很强的季节性特征,可能是由于岛屿陆架沉积物铁源的持续供应和补给;2)在南极半岛东北部和乔治亚海盆的POC储量和NCP差异不大的条件下,两个海域的夏季POC输出通量分别为7.12±3.90 mmol·m-2·d-1和45.29±5.40 mmol·m-2·d-1,乔治亚海盆区域更高的季节输出通量可能是由于混合层加深而造成的;3)结合同期的沉积物捕获器观测结果,估算乔治亚海盆的Martin衰减系数b为0.82,表明该区域具有更高的生物泵效率,与前人认为研究海域存在HPLE现象的结论有所不同,表明覆盖了整个浮游植物生长季节的BGC-Argo可更准确地量化与评估海洋生物地球化学过程和固碳能力。

衷心感谢两位匿名审稿专家和期刊编辑对本文提出的宝贵意见。本文所使用的BGC-Argo数据是由南大洋碳和气候观测与建模(SOCCOM)项目收集并免费提供的,该项目由美国国家科学基金会极地计划(NSF PLR-1425989和OPP-1936222)资助,并得到NASA、国际Argo计划和NOAA的支持。其中,Argo计划是全球海洋观测系统的一部分(http://www.argo.ucsd.edu,http://argo.jcommops.org)。

References

Publishing order | Descend order by publishing year | Descend order by cited within
[1]
GRUBER N, LANDSCHÜTZER P, LOVENDUSKI N S. The variable Southern Ocean carbon sink[J]. Annual Review of Marine Science, 2019, 11: 159-186.

DOI PMID

[2]
MARTIN J H. Glacial-interglacial CO2 change: The iron hypothesis[J]. Paleoceanography, 1990, 5(1): 1-13.

DOI

[3]
YOON J E, YOO K C, MACDONALD A M, et al. Reviews and syntheses: Ocean iron fertilization experiments-past, present, and future looking to a future Korean Iron Fertilization Experiment in the Southern Ocean (KIFES) project[J]. Biogeosciences, 2018, 15(19): 5847-5889.

DOI

[4]
BOYD P W, JICKELLS T, LAW C S, et al. Mesoscale iron enrichment experiments 1993-2005: Synthesis and future directions[J]. Science, 2007, 315(5812): 612-617.

PMID

[5]
MARTIN P, LOEFF M R, CASSAR N, et al. Iron fertili-zation enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX[J]. Global Biogeochemical Cycles, 2013, 27(3): 871-881.

DOI

[6]
PERISSINOTTO R, LAUBSCHER R K, MCQUAID C D. Marine productivity enhancement around Bouvet and the South Sandwich Islands (Southern Ocean)[J]. Marine Ecology Progress Series, 1992, 88(1): 41-53.

DOI

[7]
PERISSINOTTO R, LUTJEHARMS J, VAN BALLEGOOYEN R. Biological-physical interactions and pelagic productivity at the Prince Edward Islands, Southern Ocean[J]. Journal of Marine Systems, 2000, 24(3): 327-341.

DOI

[8]
CAVAGNA A J, FRIPIAT F, ELSKENS M, et al. Biological productivity regime and associated N cycling in the vicinity of Kerguelen Island area, Southern Ocean[J]. Biogeosciences Discussions, 2014, 11(12): 18073-18104.

[9]
ARRIGO K R, VAN DIJKEN G L, ALDERKAMP A C, et al. Early spring phytoplankton dynamics in the western Antarctic peninsula[J]. Journal of Geophysical Research: Oceans, 2017, 122(12): 9350-9369.

DOI

[10]
KORB R E, WHITEHOUSE M. Contrasting primary production regimes around South Georgia, Southern Ocean: Large blooms versus high nutrient, low chlorophyll waters[J]. Deep Sea Research Part I: Oceanographic Research Papers, 2004, 51(5): 721-738.

DOI

[11]
MATANO R P, COMBES V, YOUNG E F, et al. Modeling the impact of ocean circulation on chlorophyll blooms around South Georgia, Southern Ocean[J]. Journal of Geophysical Research: Oceans, 2020, 125(9): e2020JC016391.

[12]
MONGIN M, MOLINA E, TRULL T W. Seasonality and scale of the Kerguelen Plateau phytoplankton bloom: A remote sensing and modeling analysis of the influence of natural iron fertilization in the Southern Ocean[J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2008, 55(5/6/7): 880-892.

DOI

[13]
MARALDI C, MONGIN M, COLEMAN R, et al. The influence of lateral mixing on a phytoplankton bloom: Distribution in the Kerguelen Plateau region[J]. Deep Sea Research Part I: Oceanographic Research Papers, 2009, 56(6): 963-973.

DOI

[14]
POLLARD R T, VENABLES H J, READ J F, et al. Large-scale circulation around the Crozet Plateau controls an annual phytoplankton bloom in the Crozet Basin[J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2007, 54(18/19/20): 1915-1929.

DOI

[15]
PLANQUETTE H, STATHAM P J, FONES G R, et al. Dissolved iron in the vicinity of the Crozet Islands, Southern Ocean[J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2007, 54(18/19/20): 1999-2019.

DOI

[16]
BORRIONE I, SCHLITZER R. Distribution and recurrence of phytoplankton blooms around South Georgia, Southern Ocean[J]. Biogeosciences, 2013, 10(1): 217-231.

DOI

[17]
GILPIN L C, PRIDDLE J, WHITEHOUSE M J, et al. Primary production and carbon uptake dynamics in the vicinity of South Georgia-balancing carbon fixation and removal[J]. Marine Ecology Progress Series, 2002, 242: 51-62.

DOI

[18]
SCHLOSSER C, SCHMIDT K, AQUILINA A, et al. Mechanisms of dissolved and labile particulate iron supply to shelf waters and phytoplankton blooms off South Georgia, Southern Ocean[J]. Biogeosciences, 2018, 15(16): 4973-4993.

DOI

[19]
BORRIONE I. Island effects on marine production and circulation around the island of South Georgia, Southern Ocean[D]. Germany: Universität Bremen, 2013.

[20]
BRANDON M A, MURPHY E J, TRATHAN P N, et al. Physical oceanographic conditions to the northwest of the sub-Antarctic Island of South Georgia[J]. Journal of Geophysical Research: Oceans, 2000, 105(C10): 23983-23996.

[21]
WARD P, WHITEHOUSE M, MEREDITH M, et al. The Southern Antarctic Circumpolar Current Front: Physical and biological coupling at South Georgia[J]. Deep Sea Research Part I: Oceanographic Research Papers, 2002, 49(12): 2183-2202.

DOI

[22]
MOIGNE F, HENSON S A, CAVAN E, et al. What causes the inverse relationship between primary production and export efficiency in the Southern Ocean?[J]. Geophysical Research Letters, 2016, 43(9): 4457-4466.

DOI

[23]
WHITEHOUSE M J, KORB R E, ATKINSON A, et al. Formation, transport and decay of an intense phytoplankton bloom within the high-nutrient low-chlorophyll belt of the Southern Ocean[J]. Journal of Marine Systems, 2008, 70(1/2): 150-167.

DOI

[24]
REMBAUVILLE M, MANNO C, TARLING G A, et al. Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia[J]. Deep-Sea Research Part I: Oceano-graphic Research Papers, 2016, 115: 22-35.

[25]
AINSWORTH J, POULTON A J, LOHAN M C, et al. Iron cycling during the decline of a South Georgia diatom bloom[J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2023, 208: 105269.

DOI

[26]
CHAI F, JOHNSON K S, CLAUSTRE H, et al. Monitoring ocean biogeochemistry with autonomous platforms[J]. Nature Reviews Earth & Environment, 2020, 1(6): 315-326.

[27]
ORSI A H, WHITWORTH T, NOWLIN W D. On the meridional extent and fronts of the Antarctic Circumpolar Current[J]. Deep Sea Research Part I: Oceanographic Research Papers, 1995, 42(5): 641-673.

DOI

[28]
THORPE S E, HEYWOOD K J, BRANDON M A, et al. Variability of the southern Antarctic Circumpolar Current front north of South Georgia[J]. Journal of Marine Systems, 2002, 37(1/2/3): 87-105.

DOI

[29]
WHITEHOUSE M J, PRIDDLE J, SYMON C. Seasonal and annual change in seawater temperature, salinity, nutrient and chlorophyll a distributions around South Georgia, South Atlantic[J]. Deep Sea Research Part I: Oceanographic Research Papers, 1996, 43(4): 425-443.

DOI

[30]
JOHNSON K S, PLANT J N, COLETTI L J, et al. Biogeochemical sensor performance in the SOCCOM profiling float array[J]. Journal of Geophysical Research: Oceans, 2017, 122(8): 6416-6436.

DOI

[31]
BUESSELER K O. The decoupling of production and particulate export in the surface ocean[J]. Global Biogeochemical Cycles, 1998, 12(2): 297-310.

DOI

[32]
NELSON D M, ANDERSON R F, BARBER R T, et al. Vertical budgets for organic carbon and biogenic silica in the Pacific sector of the Southern Ocean, 1996-1998[J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2002, 49(9/10): 1645-1674.

DOI

[33]
SMITH W O, SHIELDS A R, DREYER J C, et al. Interannual variability in vertical export in the Ross Sea: Magnitude, composition, and environmental correlates[J]. Deep Sea Research Part I: Oceanographic Research Papers, 2011, 58(2): 147-159.

DOI

[34]
PINCKNEY J L. A mini-review of the contribution of benthic microalgae to the ecology of the continental shelf in the South Atlantic Bight[J]. Estuaries and Coasts, 2018, 41(7): 2070-2078.

DOI

[35]
HILLEBRAND H, SOMMER U. The nutrient stoichiometry of benthic microalgal growth: Redfield proportions are optimal[J]. Limnology and Oceanography, 1999, 44(2): 440-446.

DOI

[36]
SALLÉE J B, SPEER K G, RINTOUL S R. Zonally asymmetric response of the Southern Ocean mixed-layer depth to the Southern Annular Mode[J]. Nature Geoscience, 2010, 3(4): 273-279.

DOI

[37]
MOORE J K, ABBOTT M R. Phytoplankton chlorophyll distributions and primary production in the Southern Ocean[J]. Journal of Geophysical Research: Oceans, 2000, 105(C12): 28709-28722.

[38]
MOORE J K, ABBOTT M R, RICHMAN J G, et al. SeaWiFS satellite ocean color data from the Southern Ocean[J]. Geophysical Research Letters, 1999, 26(10): 1465-1468.

DOI

[39]
HOLM-HANSEN O, KAHRU M, HEWES C D, et al. Temporal and spatial distribution of chlorophyll-a in surface waters of the Scotia Sea as determined by both shipboard measurements and satellite data[J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2004, 51(12/13): 1323-1331.

DOI

[40]
KORB R E, WHITEHOUSE M J, WARD P. SeaWiFS in the Southern Ocean: Spatial and temporal variability in phytoplankton biomass around South Georgia[J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2004, 51(1/2/3): 99-116.

DOI

[41]
KORB R E, WHITEHOUSE M J, ATKINSON A, et al. Magnitude and maintenance of the phytoplankton bloom at South Georgia: A naturally iron-replete environment[J]. Marine Ecology Progress Series, 2008, 368: 75-91.

DOI

[42]
BORRIONE I, AUMONT O, NIELSDÓTTIR M C, et al. Sedimentary and atmospheric sources of iron around South Georgia, Southern Ocean: A modelling perspective[J]. Biogeosciences, 2014, 11(7): 1981-2001.

DOI

[43]
HOLM-HANSEN O, HEWES C D. Deep chlorophyll-a maxima (DCMs) in Antarctic waters[J]. Polar Biology, 2004, 27(11): 699-710.

DOI

[44]
TRULL T W, BRAY S G, MANGANINI S J, et al. Moored sediment trap measurements of carbon export in the Subantarctic and Polar Frontal zones of the Southern Ocean, south of Australia[J]. Journal of Geophysical Research: Oceans, 2001, 106(C12): 31489-31509.

[45]
JOUANDET M P, BLAIN S, METZL N, et al. Interannual variability of net community production and air-sea CO2 flux in a naturally iron fertilized region of the Southern Ocean (Kerguelen Plateau)[J]. Antarctic Science, 2011, 23(6): 589-596.

DOI

[46]
BOYD P W, CLAUSTRE H, LEVY M, et al. Multi-faceted particle pumps drive carbon sequestration in the ocean[J]. Nature, 2019, 568(7752): 327-335.

DOI

[47]
XING X, WELLS M, CHEN S L, et al. Enhanced winter carbon export observed by BGC-Argo in the Northwest Pacific Ocean[J]. Geophysical Research Letters, 2020, 47: e2020GL089847.

[48]
WARD P, SHREEVE R, WHITEHOUSE M, et al. Phyto-and zooplankton community structure and production around South Georgia (Southern Ocean) during Summer 2001/02[J]. Deep Sea Research Part I: Oceanographic Research Papers, 2005, 52(3): 421-441.

DOI

[49]
BELCHER A, TARLING G A, MANNO C, et al. The potential role of Antarctic krill faecal pellets in efficient carbon export at the marginal ice zone of the South Orkney Islands in spring[J]. Polar Biology, 2017, 40(10): 2001-2013.

DOI PMID

[50]
MANNO C, STOWASSER G, FIELDING S, et al. Deep carbon export peaks are driven by different biological pathways during the extended Scotia Sea (Southern Ocean) bloom[J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2022, 205: 105183.

DOI

[51]
SALTER I, KEMP A E S, MOORE C M, et al. Diatom resting spore ecology drives enhanced carbon export from a naturally iron-fertilized bloom in the Southern Ocean[J]. Global Biogeochemical Cycles, 2012, 26(1): 1-17.

[52]
BELCHER A, HENLEY S, HENDRY K, et al. Seasonal cycles of biogeochemical fluxes in the Scotia Sea, Southern Ocean: A stable isotope approach[J]. Biogeosciences, 2023, 20(6): 3573-3591.

DOI

[53]
FRANCOIS R, HONJO S, KRISHFIELD R, et al. Factors controlling the flux of organic carbon to the bathypelagic zone of the ocean[J]. Global Biogeochemical Cycles, 2002, 16(4): 34-1-34-20.

[54]
GIERING S L C, HOSKING B, BRIGGS N, et al. The interpretation of particle size, shape, and carbon flux of marine particle images is strongly affected by the choice of particle detection algorithm[J]. Frontiers in Marine Science, 2020, 7: 564.

DOI

Options
Outlines

/

〈 〉