Abstract Sinking particulate flux out of the upper ocean is a key observation of the ocean’s biological carbon cycle. Particle flux in the upper mesopelagic is often determined using sediment traps but there is no absolute standard for the measurement. Prior to this study, differing neutrally-buoyant sediment trap designs have not been deployed simultaneously, which precludes meaningful comparisons between flux data collected using these designs. The aim of the study was to compare a suite of modern methods for measuring sinking carbon flux out of the surface ocean. This study compared samples from two neutrally buoyant drifting sediment trap designs, and a surface tethered drifting sediment trap, which collected sinking particles alongside other methods for sampling particle properties, including in situ pumps and 234Th radionuclide measurements. Samples were collected at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) site in the Northeast Atlantic Ocean (49°N, 16.5°W). Neutrally-buoyant conical traps appeared to collect lower absolute fluxes than neutrally-buoyant, or surface-tethered cylindrical traps, but compositional ratios of sinking particles indicated collection of similar material when comparing the conical and cylindrical traps. In situ pump POC:234Th ratios generally agreed with trap ratios but conical trap samples were somewhat depleted in 234Th, which along with sinking particle size distribution data determined from gel traps, may imply under-sampling of small particles. Cylindrical trap POC fluxes were of similar magnitude to 234Th-derived POC fluxes while conical POC fluxes were lower. Further comparisons are needed to distinguish if differences in particle flux magnitude are due to conical versus cylindrical trap designs. Parallel analytical determinations, conducted by different laboratories, of replicate samples for elemental fluxes and gel trap particle size distributions were comparable. This study highlights that the magnitude of particle fluxes and size spectra may be more sensitive than the chemical composition of particle fluxes to the instrumentation used. Only two deployments were possible during this study so caution should be taken when applying these findings to other regions and export regimes. We recommend that multiple methodologies to measure carbon export should be employed in field studies, to better account for each method’s merits and uncertainties. These discrepancies need further study to allow carbon export fluxes to be compared with confidence across laboratory, region and time and to achieve an improved global understanding of processes driving and controlling carbon export.

中文翻译：

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所有的沉积物捕集器都是一样的吗？PAP-SO 站点碳输出方法的比对研究

摘要 从上层海洋下沉的颗粒通量是对海洋生物碳循环的一个重要观测。上层中层的粒子通量通常使用沉积物捕集器来确定，但没有绝对的测量标准。在这项研究之前，不同的中性浮力沉积物捕集器设计尚未同时部署，这排除了使用这些设计收集的通量数据之间的有意义的比较。该研究的目的是比较一套用于测量海洋表面下沉碳通量的现代方法。本研究比较了来自两种中性浮力漂流沉积物阱设计和表面系留漂流沉积物阱的样本，后者收集下沉颗粒以及其他采样颗粒特性的方法，包括原位泵和 234Th 放射性核素测量。在东北大西洋（北纬 49 度，西经 16.5 度）的豪猪深海平原持续观测站 (PAP-SO) 站点收集样品。中性浮力锥形陷阱似乎比中性浮力或表面系留圆柱形陷阱收集的绝对通量更低，但在比较锥形和圆柱形陷阱时，下沉颗粒的组成比表明收集了类似的材料。原位泵 POC:234Th 比率通常与陷阱比率一致，但锥形陷阱样本在 234Th 中有些耗尽，这与从凝胶陷阱确定的下沉粒度分布数据一起，可能意味着小颗粒采样不足。圆柱形陷阱 POC 通量与 234Th 衍生的 POC 通量具有相似的幅度，而锥形 POC 通量较低。需要进一步比较以区分粒子通量大小的差异是否是由于锥形和圆柱形陷阱设计造成的。由不同实验室对重复样品的元素通量和凝胶阱粒度分布进行的平行分析测定具有可比性。这项研究强调，粒子通量的大小和尺寸谱可能比粒子通量的化学成分对所使用的仪器更敏感。在这项研究中只能进行两次部署，因此在将这些发现应用于其他地区和出口制度时应谨慎。我们建议在实地研究中应采用多种方法来衡量碳输出，以更好地说明每种方法的优点和不确定性。