Table_1_Relationship Between Carbon- and Oxygen-Based Primary Productivity in the Arctic Ocean, Svalbard Archipelago.docx

Phytoplankton contribute half of the primary production (PP) in the biosphere and are the major source of energy for the Arctic Ocean ecosystem. While PP measurements are therefore fundamental to our understanding of marine biogeochemical cycling, the extent to which current methods provide a definitive estimate of this process remains uncertain given differences in their underlying approaches, and assumptions. This is especially the case in the Arctic Ocean, a region of the planet undergoing rapid evolution as a result of climate change, yet where PP measurements are sparse. In this study, we compared three common methods for estimating PP in the European Arctic Ocean: (1) production of 18O-labeled oxygen (GPP-18O), (2) changes in dissolved oxygen (GPP-DO), and (3) incorporation rates of 14C-labeled carbon into particulate organic carbon (14C-POC) and into total organic carbon (14C-TOC, the sum of dissolved and particulate organic carbon). Results show that PP rates derived using oxygen methods showed good agreement across season and were strongly positively correlated. While also strongly correlated, higher scatter associated with seasonal changes was observed between 14C-POC and 14C-TOC. The 14C-TOC-derived rates were, on average, approximately 50% of the oxygen-based estimates. However, the relationship between these estimates changed seasonally. In May, during a spring bloom of Phaeocystis sp., 14C-TOC was 52% and 50% of GPP-DO, and GPP-18O, respectively, while in August, during post-bloom conditions dominated by flagellates, 14C-TOC was 125% of GPP-DO, and 14C-TOC was 175% of GPP-18O. Varying relationship between C and O rates may be the result of varying importance of respiration, where C-based rates estimate net primary production (NPP) and O-based rates estimate gross primary production (GPP). However, uncertainty remains in this comparison, given differing assumptions of the methods and the photosynthetic quotients. The median O:C ratio of 4.75 in May is within the range of that observed for other regions of the world’s ocean. However, the median O:C ratio for August is

浮游植物贡献了生物圈中一半的初级生产（PP），并构成北极海洋生态系统的能量主要来源。因此，初级生产量的测量对于理解海洋生物地球化学循环至关重要。然而，鉴于不同方法在基础方法、假设上的差异，当前方法提供的确切估计程度仍然存在不确定性。尤其是在北极海洋，这一因气候变化而迅速演变的区域，初级生产量的测量数据却相对稀少。在本研究中，我们比较了三种在欧洲北极海洋中估算初级生产量的常见方法：（1）18O标记氧气的产生（GPP-18O），（2）溶解氧的变化（GPP-DO），以及（3）14C标记碳进入颗粒有机碳（14C-POC）和总有机碳（14C-TOC，溶解和颗粒有机碳的总和）的吸收速率。结果显示，使用氧气方法得出的初级生产率在季节间表现出良好的一致性，并且呈强正相关。尽管两者之间也呈现强相关性，但14C-POC与14C-TOC之间因季节变化而产生的离散度更高。基于14C-TOC得出的速率平均而言约为基于氧气估计的50%。然而，这些估计之间的关系在季节间发生变化。五月份，在硅藻属的春季爆发期间，14C-TOC分别为GPP-DO和GPP-18O的52%和50%，而八月份，在由鞭毛虫主导的 bloom 后条件下，14C-TOC为GPP-DO的125%，14C-TOC为GPP-18O的175%。碳和氧速率之间变化不定的关系可能是呼吸作用重要性变化的反映，基于碳的速率估算净初级生产（NPP），而基于氧的速率估算总初级生产（GPP）。然而，鉴于方法的不同假设和光合商的差异，这种比较的不确定性仍然存在。五月份的中位O:C比值为4.75，与世界海洋其他地区的观测值范围相符。然而，八月份的中位O:C比值则为