Southern Ocean Diatom Taphonomy and Paleoproductivity: A Laboratory Study of Silica Degradation and Export

学术价值：沉积物岩心中硅藻丰度通常被用作古初级生产力的代表。这一记录因保存情况多变而变得复杂，大部分损失发生在水体中，原因是溶解和浮游动物的摄食。本研究将通过一系列对照实验来调查解释性偏差，以创建基于与硅藻溶解和断裂相关的形态变化的原始生产力代理。PI将使用来自培养物的新鲜硅藻。具体目标包括：（1）将硅藻形态的变化与溶解的二氧化硅和其他物理和化学参数的可用性联系起来;（2）记录受控条件下的溶解过程;（3）评估随着溶解增加的硅藻形态和表面粗糙度的变化;（4）记录放牧和粪球形成对硅藻破碎和溶解的物理影响;（5）分析硅藻溶解对硅和碳输出的影响。实现这些目标的方法是：在实验室中，在不同的物理和化学条件下培养南大洋硅藻物种;对培养的硅藻进行受控的系列溶解实验;在扫描电子显微镜下对硅藻壳进行成像，分析溶解过程，并用原子力显微镜对表面结构进行微观分析;为磷虾和其他活的浮游甲壳动物提供培养物，以分析放牧和颗粒化对硅藻形态的具体影响;并将实验结果与天然浮游生物、沉积物捕集器材料以及所选的全新世、更新世和上新世沉积物岩心材料进行比较。更广泛的影响：这项工作将有助于理解硅藻丰度作为古生产力指标的用途。拟议的实验是多学科的性质。重要的是，这个项目是由一位博士设计的，而且提案大部分是由他写的。候选人这里提出的研究将导致同行评议的出版物，并为未来的研究提供一个非常有前途的科学生涯的过程中的基础。该项目还将支持NIU的一名本科研究生。PI积极参与科学外展活动，包括课堂参观、博物馆活动以及与进化和气候变化相关的网络研讨会，并积极参与国家科学基金会资助的与ANDRILL和WISSARD计划相关的外展活动。他将继续为这个项目做出努力。

Intellectual Merit: Diatom abundance in sediment cores is typically used as a proxy for paleo primary productivity. This record is complicated by variable preservation, with most loss occurring in the water column via dissolution and zooplankton grazing. This study will investigate preservational biases via a series of controlled experiments to create proxies of original productivity based on morphological changes associated with diatom dissolution and fracture. The PIs will utilize fresh diatoms from culture. Specific objectives include: (1) Linking changes in diatom morphology to availability of dissolved silica and other physical and chemical parameters; (2) Documenting the dissolution process under controlled conditions; (3) Assessment of changes in morphology and diatom surface roughness with increased dissolution; (4) Documenting the physical effects of grazing and fecal pellet formation on diatom fragmentation and dissolution; and (5) Analyzing the impact of diatom dissolution on silica and carbon export. These objectives will be achieved by growing Southern Ocean diatom species in the laboratory under differing physical and chemical conditions; controlled serial dissolution experiments on cultured diatoms; analysis of the dissolution process by imaging frustules under scanning electron microscopy (SEM) and with micro-analysis of surface texture by atomic force microscopy (AFM); making the cultures available to krill and other live zooplankton crustaceans in order to analyze the specific effects of grazing and pelletization on diatom morphology; and comparing experimental results with natural plankton, sediment trap material, and selected Holocene, Pleistocene and Pliocene sediment core material. Broader impacts: This work will contribute to understanding of the use of diatom abundance as an indicator of paleoproductivity. The proposed experiments are multi-disciplinary in nature. Importantly, the project was designed, and the proposal largely written, by a Ph.D. candidate. The research proposed here will lead to peer-reviewed publications and provide a base for future studies over the course of an extremely promising scientific career. The project will also support an undergraduate research student at NIU. The PI is heavily involved in science outreach, including classroom visits, museum events and webinars related to evolution and climate change, and is active with NSF-funded outreach activities linked to the ANDRILL and WISSARD programs. He will continue these efforts with this project.