Gross Primary Production data collected from the K-Axis voyage of the Aurora Australis, 2016

Gross Primary Production
Six depths were sampled per CTD station ranging from near-surface to 125 m. Sample depths were based on downward fluorescence profiles and two of six samples always included both near-surface (approximately 5-10 m) and the depth of the chlorophyll maximum where applicable.
Photosynthetic rates were determined using radioactive NaH14CO3. Incubations were conducted according to the method of Westwood et al. (2011). Cells were incubated for 1 hour at 21 light intensities ranging from 0 to 1200 µmol m-2 s-1 (CT Blue filter centred on 435 nm). Carbon uptake rates were corrected for in situ chlorophyll a (chl a) concentrations (µg L-1) measured using high performance liquid chromatography (HPLC, Wright et al. 2010), and for total dissolved inorganic carbon availability, analysed according to Dickson et al. (2007). Photosynthesis-irradiance (P-I) relationships were then plotted in R and the equation of Platt et al. (1980) used to fit curves to data using robust least squares non-linear regression. Photosynthetic parameters determined included light-saturated photosynthetic rate [Pmax, mg C (mg chl a)-1 h-1], initial slope of the light-limited section of the P-I curve [α, mg C (mg chl a)-1 h-1 (µmol m-2 s-1)-1], light intensity at which carbon-uptake became maximal (calculated as Pmax/ α = Ek, µmol m-2 s-1), intercept of the P-I curve with the carbon uptake axis [c, mg C (mg chl a)-1 h-1] , and the rate of photoinhibition where applicable [β, mg C (mg chl a)-1 h-1 (µmol m-2 s-1)-1].
Gross primary production rates were modelled using R. Depth interval profiles (1 m) of chl a from the surface to 200 m were constructed through the conversion of up-cast fluorometry data measured at each CTD station. For conversions, pooled fluorometry burst data from all sites and depths was linearly regressed against in situ chl a determined using HPLC. Gross daily depth-integrated water-column production was then calculated using chl a depth profiles, photosynthetic parameters (Pmax, α , β, see above), incoming climatological PAR, vertical light attenuation (Kd), and mixed layer depth. Climatological PAR was based on spatially averaged (49 pixels, approx. 2 degrees) 8 day composite Aqua MODIS data (level 3, 2004-2017) obtained for Julian day 34. Summed incoming light intensities throughout the day equated to mean total PAR provided by Aqua MODIS. Kd for each station was calculated through robust linear regression of natural logarithm-transformed PAR data with depth. In cases where CTD stations were conducted at night, Kd was calculated from a linear relationship established between pooled chlorophyll a concentrations and Kd’s determined at CTD stations conducted during the day (Kd = -0.0421 chl a * -0.0476). Mixed layer depths were calculated as the depth where density (sigma) changed by 0.05 from a 10 m reference point. Gross primary production was calculated at 0.1 time steps throughout the day (10 points per hour) and summed.

总初级生产力（Gross Primary Production）
每个温盐深（CTD）测站设置6个采样深度，覆盖范围从近表层至125米。采样深度依据下行荧光剖面确定，且6个样品中始终有2个分别对应近表层（约5~10米）以及适宜条件下的叶绿素最大值深度。

光合速率采用放射性标记碳酸氢钠（NaH¹⁴CO₃）测定。培养实验参照Westwood等人（2011）的方法开展：将样品置于21个光照强度梯度（0~1200 µmol·m⁻²·s⁻¹，使用中心波长435 nm的CT Blue滤光片）下培养1小时。碳摄取速率需针对原位叶绿素a（chl a）浓度（单位：µg·L⁻¹，采用高效液相色谱法（High Performance Liquid Chromatography, HPLC）测定，Wright et al. 2010）以及总溶解无机碳可用性（参照Dickson et al. 2007的方法分析）进行校正。随后在R语言环境中绘制光合-辐照度（P-I）关系曲线，并采用Platt等人（1980）提出的方程，通过稳健最小二乘非线性回归对数据进行曲线拟合。所获取的光合参数包括：光饱和光合速率[Pmax，单位：mg C·(mg chl a)⁻¹·h⁻¹]、P-I曲线光限制阶段的初始斜率[α，单位：mg C·(mg chl a)⁻¹·h⁻¹·(µmol·m⁻²·s⁻¹)⁻¹]、碳摄取速率达到最大值时的光照强度（计算公式为Pmax/α = Ek，单位：µmol·m⁻²·s⁻¹）、P-I曲线与碳摄取轴的截距[c，单位：mg C·(mg chl a)⁻¹·h⁻¹]，以及适宜条件下的光抑制速率[β，单位：mg C·(mg chl a)⁻¹·h⁻¹·(µmol·m⁻²·s⁻¹)⁻¹]。

总初级生产力速率通过R语言建模计算。基于各CTD测站获取的上行荧光剖面数据，转换得到表层至200米范围内、分辨率为1米的叶绿素a深度剖面。转换过程中，将所有站位及深度的荧光脉冲数据合并，与采用HPLC测定的原位叶绿素a浓度进行线性回归分析。随后结合叶绿素a深度剖面、光合参数（Pmax、α、β，详见前文）、气候学平均入射光合有效辐射（Photosynthetically Active Radiation, PAR）、垂直光衰减系数（Kd）以及混合层深度，计算得到每日水深积分总初级生产力。气候学平均PAR数据取自2004-2017年的Aqua MODIS 8天合成三级产品（Level 3），空间范围为49个像素（约2°），对应儒略日34。当日总入射光照强度之和等同于Aqua MODIS提供的平均总PAR值。各测站的Kd值通过对经自然对数转换的PAR数据与深度进行稳健线性回归计算得到。若CTD测站在夜间开展，则基于合并的叶绿素a浓度与日间CTD测站获取的Kd值建立的线性关系（公式：Kd = -0.0421×chl a × -0.0476）计算Kd值。混合层深度以10米参考点处的密度（σ）变化0.05对应的深度为准。总初级生产力以每日0.1小时为时间步长（每小时10个计算点）进行逐点计算后求和。