Sediment trap fecal pellets enumerations collected aboard CCE LTER process cruises in the California Current system, 2007, 2008 and 2016.

The collection and enumeration of sinking fecal pellets on CCE LTER Process cruises has been led by Mike Stukel since 2007. Sinking particles are collected in VERTEX-style particle interceptor traps (PIT) with an 8:1 aspect ratio, 70-mm diameter, and a baffle on top comprised of 13 smaller beveled tubes with a similar 8:1 aspect ratio. Tubes are deployed with a formalin-brine for a duration of 2-5 days. After recovery, samples are gently split on a Folsom splitter and typically 3/8 to 1/2 of two separate tubes are utilized for fecal pellet enumeration. After the cruise, samples for fecal pellet enumeration are placed in a settling chamber to allow fecal pellets to settle out. Overlying water is then strained through a 60-um filter to collect any pellets that may have remained in the water. Pellets were then placed on a gridded Petri dish and analyzed using a Zeiss Discovery stereomicroscope. Pellets were separated from other particles and photographed with a dedicated camera. Image processing was then conducted using either Image J or Image Pro to extract area and maximum feret length for each fecal pellet. Pellets were classified by shape and shape-appropriate equations were used to determine the volume of each fecal pellet. Volume was converted to mass using the equations in Stukel et al. (2013). ‘Sample’ refers to which of two samples the fecal pellet was contained within. ‘PelletID’ is the identifier for each fecal pellet in a sample. ‘Conversion Factor’ accounts for the proportion of a sample that was sorted for fecal pellets, as well as the deployment duration and cross-sectional area of the sediment trap. To determine the mass flux of fecal pellets of a certain type: 1) Sum the pellet mass for all fecal pellets of that type in a given sample and 2) multiply by the Conversion factor for that sample. ‘Shape’ is an identifier for the shape of a fecal pellet: 1) ovoid, 2) cylindrical, 3) spherical, 4) tabular, 5) amorphous, 6) ellipsoidal, 7) degraded fecal material. For more details please see Stukel et al. (2013) or Morrow et al. (submitted). Knauer, G. A., J. H. Martin and K. W. Bruland (1979). "Fluxes of particulate carbon, nitrogen, and phosphorus in the upper water column of the Northeast Pacific." Deep-Sea Research 26(1): 97-108. Morrow, R. M., M. D. Ohman, R. Goericke, T. B. Kelly, M. R. Landry, B. M. Stephens and M. R. Stukel (submitted). "Primary Productivity, Mesozooplankton Grazing, and the Biological Pump in the California Current Ecosystem: Variability and Response to El Niño." Deep-Sea Research I. Stukel, M. R., M. D. Ohman, C. R. Benitez-Nelson and M. R. Landry (2013). "Contributions of mesozooplankton to vertical carbon export in a coastal upwelling system." Marine Ecology Progress Series 491: 47-65.

自2007年起，迈克·斯图克尔（Mike Stukel）主导了加州海流长期生态研究（CCE LTER）航次中沉降粪球的收集与计数工作。沉降颗粒采用VERTEX型颗粒拦截捕集器（particle interceptor traps, PIT）收集，该捕集器长径比为8:1，直径70毫米，顶部挡板由13根带斜切口的小型管材组成，同样采用8:1的长径比。捕集器采用福尔马林-盐水溶液进行固定，部署时长为2至5天。回收样品后，使用福尔斯姆分样器（Folsom splitter）对样品进行轻柔分样，通常选取两根独立捕集管中3/8至1/2的子样用于粪球计数。航次结束后，用于粪球计数的样品被置于沉降室中，使粪球自然沉降；随后将上层水体通过60微米滤膜（60-μm filter）过滤，以收集残留在水体中的粪球。将收集到的粪球转移至带网格的培养皿中，使用蔡司Discovery体视显微镜进行分析，将粪球与其他颗粒分离后，使用专用相机进行拍照。后续通过Image J或Image Pro软件进行图像处理，提取每颗粪球的面积及最大费雷特长度（maximum feret length）。根据形状对粪球进行分类，并采用适配形状的计算公式确定每颗粪球的体积；通过斯图克尔等人2013年提出的公式，将体积转换为质量。
术语说明如下："Sample（样品）"指粪球所属的两份子样之一；"PelletID（粪球标识）"为单一样品中每颗粪球的唯一标识符；"Conversion Factor（转换系数）"用于校正用于粪球计数的子样占比、捕集器部署时长以及沉积物捕集器的横截面积。
特定类型粪球的质量通量计算步骤为：1）汇总给定子样中该类型所有粪球的总质量；2）乘以该子样对应的转换系数。"Shape（形状类别）"为粪球的形状标识，共分为7类：1）卵形；2）圆柱形；3）球形；4）片状；5）无定形；6）椭球形；7）降解粪粒。
更多细节可参考斯图克尔等人2013年的研究，或莫罗等人已投稿的论文。
参考文献：
1. Knauer, G. A., J. H. Martin 与 K. W. Bruland (1979). 《东北太平洋上层水体中颗粒态碳、氮和磷的通量》，《深海研究》(Deep-Sea Research) 26(1): 97-108。
2. Morrow, R. M., M. D. Ohman, R. Goericke, T. B. Kelly, M. R. Landry, B. M. Stephens 与 M. R. Stukel (已投稿). 《加州海流生态系统的初级生产力、中型浮游动物摄食与生物泵：变异及其对厄尔尼诺的响应》，《深海研究I辑》(Deep-Sea Research I)。
3. Stukel, M. R., M. D. Ohman, C. R. Benitez-Nelson 与 M. R. Landry (2013). 《沿岸上升流系统中中型浮游动物对垂直碳输出的贡献》，《海洋生态学进展系列》(Marine Ecology Progress Series) 491: 47-65。