Comparative study of processes controlling carbon export in Southern Ocean environments characterised by a different hydrodynamical and ecological functioning

Preliminary Metadata record for data expected from ASAC Project 1343
See the link below for public details on this project.
Comparative study of the processes controlling carbon export in Southern Ocean environments characterised by a different hydrodynamical and ecological functioning.

Work on this project was carried out on Voyage 3 of the Aurora Australis (CLIVAR) of the 2001 and 2002 season.

Work at sea target sampling sites were the 8 'particle stations' along the CLIVAR SR3 repeat transect: the SAZ at 47 degrees and 49 degrees S; the SAF at 51 degrees S; the PFZ at 54 degrees S; the IPFZ at 57 degrees S; the SPZ at 59 degrees and 61 degrees S; the SACCF at 63 degrees S and the SSIZ at 64 degrees S. Some of these (64 degrees, 61 degrees and 51 degrees S) were sampled again on the way back to assess temporal evolution. All proxy studies (new production; Ba; delta30Si; 234Th-deficit) were done at each particle station but not necessarily on the same CTD casts.

New production assessment Surface water (at 5, 25, 50 and 70m) was sampled with the CTD rosette at all particle stations. Different aliquots of 1L seawater were spiked with 15N-nitrate, 15N-ammonium or 15N-urea. All samples were spiked with 13C-bicarbonate; the latter in order to assess net primary production rates. Incubations (12 H) were done in a thermo stated algal cabinet, using appropriate neutral density screens for samples from depths below 5m. The samples were submitted to a constant light flux of 0.7x10power16 quanta/cm2/sec. Furthermore, samples from 5m depth were amended with increasing doses of ammonium (+0.1 micro M; +0.25 micro M; +0.5 micro M and +1 micro M) having natural 15N/14N abundance to assess susceptibility of N-uptake (ammonium, nitrate, urea) to ammonium. Similar experiments were run for three iron amended and control cultures in collaboration with Pete Sedwick, Dave Hutchins and Phil Boyd. Analysis of ammonium related to the incubation work was done on board by colorimetry. As a side product we obtained ammonium profiles at all particle stations and also six shallow CTD's in the southern part of the transect (greater than 61 degrees S).

Suspended particle sampling for trace element analysis and isotopic composition of Si For biogenic-Ba was also carried out. Typically 14 depths were sampled between the surface and 1000m. On board filtration was performed on Nuclepore membranes. These were dried (60 degrees C) and stored for analysis in the shore-based lab. Occasionally, we also sampled large particles - size fractions (greater than 70 micro m and 20 less than 70 micro m) - from the upper 150m for Ba, using the bow pump system of Tom Trull. Ba and Sr incubations on large settling particles sampled with the Snatcher were also performed at 5 particle stations. For delta30Si, all 24 depths of the deep CTD casts at the particle stations 1 to 8 were sampled. Filtered seawater and suspended matter filtered on Nuclepore membranes (dried at 60 degrees C) were saved for later analysis in the home based laboratory.

234Th work - we refer to the report by Ken Buesseler for the major part of this work. In addition we performed some work using the 'Snatcher' Large Volume sampler and sedimentation column. Total 234Th deficit and 234Th activity on particles and solution was assessed at T0 and T4 H after return of the sampling device on board, in an attempt to construct the 234Th mass balance and eventually get at the settling speed (and flux) of 234Th carrying particles. These analyses went together with flow cytometry analyses (collaboration with Clive Crossley) to check for sedimentation by (fluorescent) particles and also with POC and biogenic silica in order to determine the elemental ratios of suspended and sinking particles. Flow cytometer results did not indicate there was significant sedimentation of life cells going on at this time of the year.

Dissolved Ba Seawater samples were taken at all depths sampled by deep CTD's during the southward transect. Samples were acidified and kept for later analysis of dissolved barium by isotope dilution ICP-MS. Comparison of the dissolved Ba distribution along the transect with the one reconstructed through a multiple end-member mixing model will help understanding of the relative contribution of in-situ processes (uptake, dissolution) versus conservative mixing, thus improving our understanding of the oceanic Ba biogeochemistry.

Analysis
New production. Isotope ratio analysis of the 15N and 13C spiked natural plankton samples will be conducted in the home lab., using emission spectrometry and mass spectrometry. Mass balance calculations will allow assessing relative importance of new production as well as the fraction of new production that is in the particulate form and represents the potential for export.

Ba and trace elements. Suspended matter samples will be acid digested (HNO3, HCl, HF) and analysed per ICP-MS and ICP-AES for contents of Ba, Ca, Sr, Al, Fe, Mn, Th, U, REE, Ti. The vertical concentration profiles will inform on the latitudinal and temporal variability of the biogeochemical control processes between SAZ, PFZ, ACC and SSIZ subsystems. For the sites with sediment trap deployments, particulate trace element distributions in the water column will be compared with trace element composition of fast settling particles intercepted by the traps.

Ba-uptake / barite formation. Isotope ratio analysis (135Ba/138Ba; 86Sr/87Sr) of suspended matter incubated after spiking with 135Ba and 86Sr will be analysed by ICP-MS to investigate on the barite formation process. Abundance and type of barite crystals will be studied by SEM-EMP (mapping + photographs). delta30Si, In the home based lab. particle samples will be extracted using base (NaOH). Silicates in filtered seawater will be precipitated and analysed using a multi collector ICP-sectorial Mass Spectrometer (MC-ICP-MS) once this new method is set up.

234Th. Total, particulate and dissolved 234Th measurements were performed on board using low beta counters. Background (after 6 months decay) and chemical yields will be measured at Ken Buesseler's lab (WHOI, USA), using beta counters and ICP-MS respectively.

The worksheets contained in the excel spreadsheet are:
Phyo biomass
New production and cell counts
Particulate barium
Dissolved barium
d29Si isotope signature of dissolved silicic acid

The fields in this dataset are:

Carbon
Seawater
CLIVAR
temperature
pressure
salinity
depth
barium
latitude
longitude
oxygen
silicate
phophate
nitrate
flagellates
diatoms
picoplankton
plankton
urea
ammonia
coccolithophores

# 本数据集为ASAC项目1343的预期数据初步元数据记录
请点击下方链接查看该项目的公开详情。

本项目旨在对比研究不同水动力与生态功能特征的南大洋环境中，调控碳输出的核心过程。

本项目的实地工作依托2001-2002航次的“南极光号”（Aurora Australis）第3航次（CLIVAR）开展。

本次海上调查的目标采样站位为CLIVAR SR3重复断面上的8个“粒子站位”：南纬47°、49°的亚南极带（SAZ）；南纬51°的亚南极锋（SAF）；南纬54°的极锋带（PFZ）；南纬57°的次极锋带（IPFZ）；南纬59°、61°的南极带（SPZ）；南纬63°的南南极绕极流锋（SACCF）以及南纬64°的南海冰带（SSIZ）。其中南纬64°、61°和51°的站位在返航途中被再次采样，以评估过程的时间演化特征。所有替代指标研究（新生产力、钡（Ba）、δ³⁰Si、²³⁴Th亏损）均在每个粒子站位开展，但未必在同一温盐深剖面仪（CTD）采样中完成。

## 新生产力评估
所有粒子站位均通过温盐深采水器（CTD Rosette）采集5m、25m、50m及70m深度的表层水样。每份1升的海水样品被分别添加¹⁵N标记的硝酸盐、铵盐或尿素；所有样品均添加¹³C标记的碳酸氢盐，以评估净初级生产力速率。培养实验（时长12小时）在控温藻类培养箱中进行，对于5m以下深度的样品，需使用合适的中性密度滤光片调节光照，样品接收的恒定光通量为0.7×10¹⁶ 量子/平方厘米/秒。

此外，针对5m深度的水样，添加不同梯度的天然¹⁵N/¹⁴N丰度的铵盐（浓度梯度为+0.1μM、+0.25μM、+0.5μM及+1μM），以评估氮摄取（铵盐、硝酸盐、尿素）对铵盐的响应敏感性。本研究与Pete Sedwick、Dave Hutchins及Phil Boyd合作，针对3组铁添加培养组与对照组开展了类似实验。与培养实验相关的铵盐分析在船上通过比色法完成。作为附加成果，我们获取了所有粒子站位的铵盐垂直剖面，以及断面南部（南纬61°以南海域）的6个浅层温盐深剖面数据。

## 悬浮颗粒物采样与分析
本研究还采集了悬浮颗粒物样品，用于微量元素分析、硅同位素组成测定，以及生物源钡（biogenic-Ba）的相关研究。通常在表层至1000m水深范围内采集14个深度的样品，船上采样阶段采用Nuclepore膜进行过滤，过滤后的膜置于60℃下烘干，随后保存至岸基实验室以待分析。

偶尔，我们还借助Tom Trull的船首泵系统，从表层150m水深中采集大粒径颗粒物样品——分为>70μm及20<70μm两个粒径组分——以分析钡元素含量。本研究还在5个粒子站位开展了针对“Snatcher”采样器采集的大型沉降颗粒物的钡（Ba）与锶（Sr）培养实验。针对δ³⁰Si分析，我们采集了1至8号粒子站位的深层温盐深剖面的全部24个深度的样品。过滤后的海水以及通过Nuclepore膜过滤得到的悬浮颗粒物（60℃烘干）均被保存，以待岸基实验室开展后续分析。

## ²³⁴Th相关研究
关于²³⁴Th相关工作，本研究的大部分内容参考了Ken Buesseler的相关报告。此外，我们还借助“Snatcher”大体积采样器与沉降柱开展了部分实验。在采样装置回收至船上后的T0及T4小时节点，我们分别测定了颗粒物与溶液中的总²³⁴Th亏损量及²³⁴Th活度，以期构建²³⁴Th的质量平衡模型，最终获取携带²³⁴Th的颗粒物的沉降速率（及沉降通量）。

这些分析与流式细胞术分析（与Clive Crossley合作）同步开展，用于检测（荧光标记）颗粒物的沉降情况；同时还与颗粒有机碳（POC）及生物源硅分析结合，以确定悬浮颗粒物与沉降颗粒物的元素比值。流式细胞仪的结果显示，在本航次开展时段，活体细胞并未发生显著沉降。

## 溶解态钡分析
南向断面调查期间，我们采集了深层温盐深剖面覆盖的所有深度的海水样品。样品经酸化处理后保存，以待后续通过同位素稀释电感耦合等离子体质谱法（ID-ICP-MS）测定溶解态钡含量。将断面沿线的溶解态钡分布与通过多端元混合模型重建的分布进行对比，有助于明确原位过程（摄取、溶解）与保守混合过程的相对贡献占比，从而深化对海洋钡生物地球化学循环的认识。

## 后续分析计划
### 新生产力分析
针对添加¹⁵N与¹³C标记物的天然浮游生物样品，本研究将在岸基实验室通过发射光谱法与质谱法开展同位素比值分析。通过质量平衡计算，可评估新生产力的相对重要性，以及以颗粒态形式存在、具备输出潜力的新生产力占比。

### 钡与微量元素分析
悬浮颗粒物样品将经硝酸（HNO₃）、盐酸（HCl）及氢氟酸（HF）消解后，通过电感耦合等离子体质谱法（ICP-MS）与电感耦合等离子体原子发射光谱法（ICP-AES）测定钡（Ba）、钙（Ca）、锶（Sr）、铝（Al）、铁（Fe）、锰（Mn）、钍（Th）、铀（U）、稀土元素（REE）及钛（Ti）的含量。垂直浓度剖面将用于揭示亚南极带（SAZ）、极锋带（PFZ）、南极绕极流（ACC）及南海冰带（SSIZ）各子系统间生物地球化学调控过程的纬度与时间变异特征。对于部署了沉积物捕集器的站位，我们将对比水柱中颗粒物的微量元素分布与捕集器截留的快速沉降颗粒物的微量元素组成。

### 钡摄取/重晶石形成过程分析
针对添加¹³⁵Ba与⁸⁶Sr标记物的悬浮颗粒物培养样品，我们将通过ICP-MS开展同位素比值分析（¹³⁵Ba/¹³⁸Ba；⁸⁶Sr/⁸⁷Sr），以探究重晶石的形成过程。重晶石晶体的丰度与形貌将通过扫描电子显微镜-电子探针显微分析（SEM-EMP，包含mapping与成像）进行研究。

针对δ³⁰Si分析：待新方法建立后，我们将在岸基实验室通过强碱（NaOH）萃取颗粒物样品，将过滤海水中的硅酸盐沉淀后，通过多接收杯电感耦合等离子体质谱仪（MC-ICP-MS）开展分析。

### ²³⁴Th分析
总²³⁴Th、颗粒态²³⁴Th及溶解态²³⁴Th的测定均在船上通过低本底β计数器完成。本底值（经6个月衰变后）与化学产率将分别在美国伍兹霍尔海洋研究所（WHOI）Ken Buesseler的实验室中，通过β计数器与ICP-MS进行测定。

## 数据集附属表格
Excel表格中包含的工作表如下：
1. 浮游植物生物量
2. 新生产力与细胞计数
3. 颗粒态钡
4. 溶解态钡
5. 溶解态硅酸的δ²⁹Si同位素特征

## 数据集字段
本数据集包含的字段如下：
碳、海水、CLIVAR（气候变率与可预报性计划）、温度、压力、盐度、深度、钡、纬度、经度、溶解氧、硅酸盐、磷酸盐、硝酸盐、鞭毛藻、硅藻、超微型浮游生物、浮游生物、尿素、氨（铵）、颗石藻