Collaborative Research: Assessing the relative importance of small vs large particles as sources of nutrition to abyssal communities

海洋的深海平原覆盖了大约一半的地球表面，蕴藏着巨大的生物多样性和矿产资源，在养分循环和碳固存方面发挥着重要作用。控制这些生态系统结构和功能的最重要的过程是到达深海海底的食物(主要是下沉的有机颗粒)的数量和质量。然而，我们并不完全了解为这个巨大的生态系统提供资源的过程。我们建议利用各种食物来源中氨基酸的稳定同位素特征，评估沉入深海底栖群落的小颗粒和大颗粒“海洋雪”的相对重要性，并追踪海底动物对它们的消耗。该项目比较了加利福尼亚州附近多产水域的生态系统和夏威夷北部营养不良的中太平洋地区的生态系统。该项目对表层海洋过程如何与深海海底的食物网相联系，以及食物来源的变化如何潜在地影响深海社区提供了新的见解。该项目还为密歇根大学和南加州大学的研究生、博士后研究员和本科生，特别是攻读地球科学专业的少数族裔提供了极好的培训机会。该项目将赞助一年一度的G6-12教师讲习班，向夏威夷教育工作者介绍深海情况，并向社区广泛传播知识。所有结果都被广泛通报，以告知公众对深海生态系统的关切因对深海采矿的兴趣而增加。控制深海生态系统结构和功能的最重要过程是最终到达深海海底的有机物质的数量和质量。尽管真光带出口通量与底栖生物生态之间存在密切关系，但对深海生态系统的研究发现，食物供应与底栖生物群落需求之间存在缺口。因此，需要开展更多的工作，特别是在了解深海底栖动物的营养来源方面。最近的证据表明，小颗粒可能是碳输出的重要贡献者，其相对重要性随着中层海洋深度的增加而增加，并到达深海海底。该项目旨在结合两个深海地点的颗粒通量测量和最新的氨基酸化合物特定稳定同位素分析(AA-CSIA)，评估较小和较大的“海洋雪”颗粒对深海底栖生物群落的相对重要性。这些地点的时间序列测量(Sta.我要离开加利福尼亚和斯塔。夏威夷近海的Aloha)为这项工作提供了丰富的背景。在北太平洋中部的中层大气中，可以使用AA-CSIA从经过微生物改造的较小(0.7-53微米)粒子中分离出较大的粒子(53微米)。该项目正在利用海底附近和底部系泊沉积物捕集器附近的现场过滤收集的一系列颗粒(从1.0微米悬浮颗粒到大下沉颗粒53微米)中的关键单个化合物的同位素组成，从而确定可追踪到海底动物和沉积物(由遥控潜水器和底栖雪橇收集)的特定来源的同位素特征。这项研究旨在利用化合物一级的同位素测量来了解从颗粒到大型动物的中上层-底栖动物之间的耦合，这将为小型微生物改造颗粒对深海海底食物网的重要性提供新的见解。这将更准确地将表层海洋过程与深海海底的食物网结合起来，这将对了解气候变化的影响和向营养较高水平转移能量的效率产生影响。此外，同位素测量还可以用来通过量化不同大小类别的营养位置来进一步参数化生态系统模型，从而估计与身体大小光谱、功能类型以及最终与碳通量和再矿化有关的捕食者-猎物质量比率。最后，这一结果将有助于通过校准表层和海底档案之间有机质同位素值的潜在变化来完善对过去氮动力学的深海古记录的解释。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The abyssal plains of the oceans cover roughly half of the earth's surface, host enormous reservoirs of biodiversity and mineral resources, and play important roles in nutrient recycling and carbon sequestration. The most important process controlling the structure and function of these ecosystems is the quantity and quality of food (mostly sinking organic particles) that reaches the deep-sea floor. However, we do not fully understand the processes provisioning this vast ecosystem. We propose to evaluate the relative importance of small and larger "marine snow" particles that sink to deep-sea benthic communities by using the stable isotope signature of amino acids within various food sources and trace their consumption by fauna on the seafloor. This project compares ecosystems from the productive waters off California with the nutrient poor central Pacific, north of Hawaii. This project provides novel insights into how surface ocean processes are coupled to food-webs at the deep ocean seafloor and how changes in food sources potentially impact deep-sea communities. This project also provides excellent training opportunities for graduate students, a postdoctoral researcher, and undergraduates at UH and USC, particularly underrepresented minorities who pursue majors in the geosciences. The project will sponsor an annual G6-12 teacher workshop to inform Hawaii educators about the deep sea and broadly disseminate knowledge to the community. All results are communicated broadly to inform the public as concerns regarding abyssal ecosystems are rising due to interests in deep-sea mining. The most important process controlling the structure and function of abyssal ecosystems is the quantity and quality of organic material that ultimately reaches the deep-sea floor. Despite the strong relationship between euphotic zone export flux and benthic ecology, studies of abyssal ecosystems have observed a deficit between food supply and benthic community demand. Additional work is therefore needed, particularly with regards to understanding the sources of nutrition to the deep-sea benthos. Recent evidence suggests that small particles may be significant contributors to carbon export, increasing in relative importance with depth in the mesopelagic and reaching the abyssal seafloor. This project is to evaluate the relative importance of small and larger "marine snow" particles to deep-sea benthic communities using a combination of particle flux measurements and state of the art compound specific stable isotope analysis of amino acids (AA-CSIA) at two abyssal locations that contrast in overlying productivity, seasonality, and export magnitude. Time series measurements at these locations (Sta. M off California and Sta. Aloha off Hawaii) provide a rich context for the work. In the mesopelagic central North Pacific larger particles (53 um) can be resolved from microbially reworked, smaller (0.7-53 um) particles using AA-CSIA. This project is characterizing the isotopic compositions of key individual compounds in a continuum of particle sizes ( 1.0 um suspended particles to large sinking particles 53 um) collected using in situ filtration near the seafloor and bottom-moored sediment traps, thereby defining source-specific isotopic signatures that can be traced into benthic fauna and sediments (that are collected by ROVs and epibenthic sleds). This research to understand pelagic-benthic coupling from particles to megafauna using isotopic measurements at the compound-level will yield novel insights into the importance of small microbially reworked particles to deep-sea benthic food webs. This will more precisely couple surface ocean processes to food-webs at the deep ocean seafloor with implications for understanding climate change effects and the efficiency of energy transfer to higher trophic levels. Furthermore, isotopic measurements can also be used to further parameterize ecosystem models by quantifying trophic position across size classes and thus estimate predator-prey mass ratios in relation to variation in body size spectra, functional type, and ultimately to carbon flux and remineralization. Finally, the results will help refine interpretations of deep-sea paleorecords of past nitrogen dynamics by calibrating potential changes in organic matter isotope values between the surface and seafloor archives.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.