Diatom species and biogenic particle fluxes in the Australian sector of the southern Antarctic Zone

Diatom and biogenic particle fluxes were investigated over a one-year period (2001-02) at the southern Antarctic Zone in the Australian Sector of the Southern Ocean. Two vertically moored sediment traps were deployed at 60 degrees 44.43'S 139 degrees 53.97' E at 2000 and 3800 m below sea-level. In these data sets we present the results on the temporal and vertical variability of total diatom flux, species composition and biogenic particle fluxes during a year. A detailed description of the field experiment, sample processing and counting methods can be found in Rigual-Hernandez et al. (2015).

Total fluxes of particulates at both traps were highly seasonal, with maxima registered during the austral summer (up to 1151 mg m-2 d-1 at 2000 m and 1157 mg m-2 d-1 at 3700 m) and almost negligible fluxes during winter (up to 42 mg m-2 d-1 at 2000 m and below detection limits at 3700 m). Particulate fluxes were slightly higher at 2000 m than at 3700 m (deployment average = 261 and 216 mg m-2 d-1, respectively). Biogenic silica (SiO2) was the dominant bulk component, regardless of the sampling period or depth (deployment average = 76% at 2000 and 78% at 3700 m). Highest relative contribution of opal was registered from the end of summer through early-autumn at both depths. Secondary contributors were carbonate (CaCO3) (7% at 2000 m and 9% at 3700 m) and particulate organic carbon (POC) (1.4% at 2000 m and 1.2% at 3700 m). The relative concentration of carbonate and POC was at its highest in austral spring and summer.

Diatom frustules from 61 taxa were identified over the entire experiment. The dominant species of the diatom assemblage was Fragilariopsis kerguelensis with a mean flux between 53 x 106 and 60 x 106 valves m-2 day-1 at 2000 m (annualized mean and deployment average, respectively). Secondary contributors to the diatom assemblage at 2000 and 3700 m were Thalassiosira lentiginosa, Thalassiosira gracilis var. gracilis, Fragilariopsis separanda, Fragilariopsis pseudonana, Fragilariopsis rhombica, Fragilariopsis curta and Azpeitia tabularis.

Data available: two excel files containing sampling dates and depths, raw counts, relative abundance and fluxes (valves m-2 d-1) of the diatom species, and biogenic particle fluxes found at 2000 m and 3700 m depth. Each file contains four spreadsheets: raw diatom valve counts, relative abundance of diatom species and valve flux of diatom species and biogenic particle composition and fluxes. Detailed information of the column headings is provided below.

Cup - Cup (=sample) number
Depth - vertical location of the sediment trap in meters below the surface
Mid-point date - Mid date of the sampling interval
Length (days) - number of days the cup was open

Girdle bands instead of valves were counted for Dactyliosolen antarcticus Castracane. Therefore, D. antarcticus girdles counts were not included in relative abundance calculations

本数据集针对南大洋澳大利亚扇区南极带南部海域，于2001-2002年开展了为期一年的硅藻（diatom）与生源颗粒物通量（biogenic particle fluxes）调查。研究于南纬60°44.43′、东经139°53.97′海域布设两套垂直锚泊式沉积物捕集器（sediment trap），布设水深分别为海平面下2000米与3800米。本数据集呈现了一年内总硅藻通量、物种组成及生源颗粒物通量的时间与垂向变化特征。野外实验、样品处理与计数方法的详细说明可参见Rigual-Hernandez等人（2015）的研究成果。

两套捕集器的颗粒物总通量均呈现显著季节性特征：南半球夏季通量达到峰值，2000米水深处最高达1151 mg·m⁻²·d⁻¹，3700米水深处最高达1157 mg·m⁻²·d⁻¹；冬季通量则几乎可忽略，2000米水深处仅为42 mg·m⁻²·d⁻¹，3700米水深处通量低于检测限。2000米水深的颗粒物通量略高于3700米水深，两次部署的平均通量分别为261 mg·m⁻²·d⁻¹与216 mg·m⁻²·d⁻¹。生源二氧化硅（SiO₂）是颗粒物的主要组成成分，不受采样时段与水深影响，2000米与3700米水深的平均占比分别为76%与78%。在两个水深处，蛋白石的相对占比均在夏末至初秋达到最高。次要组成成分为碳酸盐（CaCO₃，2000米与3700米水深的平均占比分别为7%与9%）与颗粒有机碳（POC，2000米与3700米水深的平均占比分别为1.4%与1.2%）。碳酸盐与POC的相对浓度在南半球春季与夏季达到峰值。

本次调查共鉴定出61个硅藻分类群的硅质壳瓣。硅藻群落的优势种为凯氏脆杆藻（Fragilariopsis kerguelensis），2000米水深处的年均通量与单次部署平均通量分别为53×10⁶个壳瓣·m⁻²·d⁻¹与60×10⁶个壳瓣·m⁻²·d⁻¹。2000米与3700米水深处的硅藻次优势类群包括：厚壁海链藻（Thalassiosira lentiginosa）、纤细海链藻纤细变种（Thalassiosira gracilis var. gracilis）、分离脆杆藻（Fragilariopsis separanda）、假美丽脆杆藻（Fragilariopsis pseudonana）、菱形脆杆藻（Fragilariopsis rhombica）、短脆杆藻（Fragilariopsis curta）以及Azpeitia tabularis。

可用数据集包含两份Excel文件，分别记录了2000米与3700米水深处的采样日期与布设水深、原始计数数据、相对丰度、硅藻物种的通量（单位：壳瓣·m⁻²·d⁻¹）以及生源颗粒物通量。每份文件包含四个工作表：硅藻壳瓣原始计数、硅藻物种相对丰度、硅藻物种壳瓣通量，以及生源颗粒物组成与通量。表头的详细说明如下：
Cup：采样杯（即样品）编号
Depth：沉积物捕集器的垂向布设水深（单位：米，相对于海平面）
Mid-point date：采样间隔的中间日期
Length (days)：采样杯的开启时长（单位：天）

注：南极直链藻（Dactyliosolen antarcticus Castracane）的计数采用环带而非壳瓣，因此该物种的环带计数未纳入相对丰度计算。