Collaborative Research: Interactions Among Deposit-Feeding, Organic Matter Diagenesis andAnimal Nutrition

沉积物取食对碳埋藏的全球影响是深远的。尽管它们只消耗一小部分沉积有机质（OM），但它们通过增加氧气渗透到沉积物中、重新分配颗粒和刺激整个混合层的成岩活动，影响OM成岩的速度和程度。沉积有机资源同时决定底栖动物的活动，并由底栖动物的活动决定。了解沉积物喂养和有机质成岩作用如何相互作用，对于建立海洋沉积物碳循环的生物/化学耦合模型至关重要。在这项研究中，Skidaway海洋学研究所和德克萨斯大学奥斯汀分校的研究人员将通过研究实验微观环境中传送带喂养的多毛纲动物（Haploscoloplos robustus）的觅食行为，研究OM成岩作用与沉积物食料生态之间的联系和反馈。沉积物OM浓度对个体摄食率、斑块密度和速率-密度相互作用的影响将从最佳觅食的角度进行研究。记录个体功能响应、沉积物混合、微生物介导的有机转化和营养同化之间的动态平衡是本研究的主要重点。为了研究生物-微生物-沉积物耦合体系，提出了一种新的基于同位素的13C示踪实验。细菌对沉积碳和标记的OM添加物的共同代谢将导致细菌合成的OM具有不同于（12C）沉积碳和添加的（13C） OM的分子13C同位素特征。将添加的标签纳入细菌氨基酸和脂肪酸池以及随后沉积的饲料生物量的测量将用于追踪碳的命运，作为粗壮菌摄食率和种群密度的函数。有机质成岩作用、微生物生产和蠕虫觅食行为和生长之间的反馈将通过独立操纵有机供应、种群密度和沉积物混合率来量化。就更广泛的影响而言，该研究项目将包括几个机构间的合作，并将涉及培训一名研究生（在德克萨斯大学）和两名来自SkIO/萨凡纳州立大学CIRE实习项目的本科生。

The global effects of deposit feeding on carbon burial are profound. Even though they consume only a small fraction of sedimentary organic matter (OM), deposit feeders influence the rate and extent of OM diagenesis by increasing oxygen penetration into sediments, redistributing particles, and stimulating diagenetic activity throughout the mixed layer. Sedimentary organic resources simultaneously determine, and are determined by, the activities of the benthic infauna. Understanding how deposit feeding and OM diagenesis interact is critical to developing realistically coupled biological/chemical models of carbon cycling in marine sediments. In this study, investigators at the Skidaway Institute of Oceanography and the University of Texas at Austin will study linkages and feedbacks between OM diagenesis and deposit-feeder ecology by examining the foraging behavior of a conveyor-belt feeding orbiniid polychaetes (Haploscoloplos robustus) in experimental microcosms. Effects of sedimentary OM concentrations on individual feeding rates, patch density, and rate x density interactions will be examined from an optimal foraging perspective. Documenting the dynamic balance among individual functional responses, sediment mixing, microbially-mediated organic transformations, and nutrient assimilation is a major focus of the proposed study. To study the coupled organism-microbe-sediment system, a novel isotopomer-based 13C tracer experiment is proposed. Bacterial co-metabolism of sedimentary carbon and labeled OM additions will lead to the formation of bacterially-synthesized OM having molecular 13C isotopic signatures that are distinct from both the (12C) sedimentary carbon and the added (13C) OM. Measurement of the incorporation of added label into a bacterial amino acid and fatty acid pools and subsequently deposit feeder biomass will be used to trace the fate of carbon as a function of H. robustus feeding rate and population density. Feedbacks among OM diagenesis, microbial production, and worm foraging behavior and growth will be quantified by independently manipulating organic supply, population density, and sediment mixing rate. In terms of broader impacts, this research project will feature several inter-institutional collaborations and will involve the training one graduate student (at UT) and two undergraduate students from the SkIO/Savannah State CIRE internship program.