Collaborative Proposal: Using Radiocarbon Measurements of Benthic Megafauna as a Tool for Assessing Bentho-Pelagic Coupling in the Marine Organic Carbon Cycle

合作提案：利用底栖巨型动物的放射性碳测量作为评估海洋有机碳循环中底栖-中上层耦合的工具

• 批准号: 0223495
• 负责人: Craig Smith
• 金额: $ 3.19万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2005-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0223495&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Using; Radiocarbon; Measurements

This project examines the seasonal variation in the nature of the organic carbon deposited on continental margins. The flux of organic carbon reaching the seabed can be quantified by using particle traps or by modeling seabed burial and regeneration rates, but the quality (i.e., its lability) has been difficult to assess on continental margins because of co-deposition with old refractory carbon from marine and terrestrial systems. Bomb Carbon-14 (C14) is a useful tracer of recently produced marine organic matter, but this signal is masked in continental margin particle?trap samples and surface sediments by the older and refractory carbon that is re-suspended and reworked from shallower marine deposits. Surface deposit feeders in continental margin systems have been shown to sequester the labile fraction of the total organic flux reaching the seabed as a result of their selective ingestive and digestive processes. Therefore, the body tissues and the gut sediments of these benthic fauna can provide a record of the labile material reaching the continental margin seafloor. Initial C14 data indicate that the body tissues of surface depositing feeders are enriched in this radioisotope by 100 to 300 per mil relative to the surface sediments in which they live and feed. Based on mass?balance C14 calculations, the labile component may comprise only a few tenths of a percent of the total organic matter in the surface seabed, yet the surface deposit feeders exhibit C14 signatures in their body tissues (+20 to +80 per mil) dominated by the local bomb?produced signal . Thorium (Th) data from continental margins suggest that as much as 50% of the recently deposited organic matter on the continental margin sea floor may pass through the guts of deposit feeders prior to microbial degradation or burial. Therefore, C14 measurements on benthic fauna can provide a unique tool for assessing the lability of organic matter reaching the seafloor and for tracking the fate of this material in the benthic food web. Many existing diagenetic models treat organic matter regeneration by microbes and deposit feeders as a batch process with a single carbon degradation constant for the bulk organic matter. The C14 data clearly show that ingestion of organic matter and digestion of this material are very selective processes. The C14 analyses from the California Borderland and the Antarctic continental margin have shown the utility of this approach for documenting variations in the organic carbon lability of surface sediments.Drs. DeMaster and Smith will expand the initial studies to enable assessment of seasonal variations in the quality of organic carbon deposited on the seabed. Particle?trap samples, benthic?faunal tissues, gut samples and surface sediments have been collected during 6 cruises to the California Borderland and 5 cruises to the Antarctic continental margin covering the major seasonal variations in organic carbon supply. Funds are requested for making 150 C14 analyses (and complementary C13, N15, and C/N measurements) on these samples so that a time series quantifying the nature and flux of organic matter reaching the seabed can be determined. They will assess not only seasonal variations in the nature of particle selection and digestive selection processes for organic matter, but also the changes in these processes as a result of feeding strategy (epibenthic surface deposit feeders, vs. subsurface deposit feeders vs. head?down subsurface deposit feeders) on the seafloor.

该项目研究了沉积在大陆边缘的有机碳性质的季节性变化。可以通过使用颗粒陷阱或建模海床埋葬和再生速率来量化有机碳的通量，但是由于与海洋和地面系统的旧难治性碳共同沉积，因此难以评估大陆边缘的质量（即其不稳定）。炸弹碳-14（C14）是最近生产的海洋有机物的有用示踪剂，但是该信号被大陆边缘颗粒中掩盖了捕获样品和表面沉积物，并由较浅的海洋沉积物重新悬浮并重新工作。大陆边缘系统中的表面沉积物馈线已显示出由于其选择性摄入和消化过程而导致的总有机通量的不稳定分数。因此，这些底栖动物动物的身体组织和肠道沉积物可以提供到达大陆边缘海底的不稳定材料的记录。最初的C14数据表明，相对于它们的寿命和饲料的表面沉积物，表面沉积喂食器的身体组织富含100至300。基于质量水平的C14计算，不稳定的组件可能仅占表面海床中有机物总的十分之一，但是地表沉积物馈线在其身体组织中表现出C14签名（每MIL +20至+80 MIL），由局部炸弹产生的信号。大陆边缘的th（Th）数据表明，在微生物降解或埋葬之前，大陆边缘海底最近沉积的有机物中多达50％可能会穿过沉积物饲养者的肠道。因此，对底栖动物区系的C14测量值可以提供一种独特的工具，以评估有机物到达海底的有机物的不稳定，并在底栖食品网中跟踪该材料的命运。许多现有的成岩模型将微生物的有机物再生和沉积喂食器视为批量降解常数的批处理过程。 C14数据清楚地表明，摄入有机物和该材料的消化是非常有选择的过程。来自加利福尼亚州边境和南极大陆边缘的C14分析表明，这种方法可以记录表面沉积物的有机碳衰变的变化。 Demaster和Smith将扩大初始研究，以评估沉积在海床上的有机碳质量的季节性变化。颗粒陷阱样品，底栖动物组织，肠道样品和表面沉积物在6次巡航到加利福尼亚州边境地区已收集，并向南极大陆边缘进行了5次巡航，涵盖了有机碳供应的主要季节性变化。要求对这些样品进行150个C14分析（以及互补的C13，N15和C/N测量值）进行资金，以便可以确定量化有机物的性质和通量到达海底的时间序列。他们不仅会评估有机物颗粒选择的性质和消化选择过程的季节性变化，还将评估由于喂养策略（表面表面储备金，与地下表面存款馈线的饲养策略）的结果，这些过程的变化是海藻的。