The Effects of Animal-Sediment Interactions on Geochemical Processes Near the Sediment-Water Interface

沉积矿床中的成岩作用在生物地球化学反应元素的循环和埋藏中起着核心作用。海洋底栖动物的活动极大地影响了早期成岩作用，改变了大部分海底表层沉积物中的物质运输和反应分布。本研究将审查、概念化和量化这些生物成因对生物地球化学循环的影响的具体方面，并将在底栖生物的共生和自生特征的背景下这样做。对生物结构的取食、挖洞和灌溉创造了复杂的、依赖于时间的缺氧和缺氧微环境网络。这些微环境的尺度和宏观几何模式决定了再矿化途径、微生物丰度和活性的绝对和相对速率，以及硝化-反硝化或碳酸盐溶解-沉淀等反应之间的耦合。在这个项目中，纽约州立大学石溪分校的研究人员将继续他们对底栖生物群落及其与沉积物化学的双向关系的观察、实验和技术发展研究。一套平面荧光传感器(平面光电二极管)设计用于在100-300平方厘米的区域内以高分辨率(约30-50微米)测量单幅图像中的pH、二氧化碳和O2，在上一次资助期间开发了部分设备，并将进一步进行优化。将开发一种复合传感器，允许同时测量O2、H+和CO2。这些荧光传感器将被用来直接研究实验室微型宇宙中功能不同的动物群产生的三维溶质分布，以及使用改装成与平面光电管一起使用的沉积物剖面相机在现场调查自然群落中的三维溶质分布。功能类型的单独和混合的影响将在多个密度下进行检验。将量化生物结构周围的再矿化率，并测试有关比例-反应关系的假设。生物结构周围微生物活动的直接测量将由光学传感模式指导。为模拟灌溉洞穴的影响而设计的扩散反应池将与光学传感器一起使用，以检查瞬时和伪稳定反应平衡以及微生物活动作为扩散传输规模的函数，以便与类似规模的自然结构进行比较。将对粘液分泌物进行扩散池测量，以进一步限制半渗透特性、DOC成分的分级和代谢模式。此外，还将对天然间质粘液和管道衬里的分解速度进行其他实验。孔隙空间的半渗透性和各向异性运移的含义将被纳入概念和数学模型。更广泛的影响：目前的研究将促进对底栖生物群落和沉积物化学之间的相互作用、它们对具有社会重要性的生物地球化学循环的影响以及污染物的去向的预测性、机械性的理解。生物地球化学应用平面荧光传感器的进一步开发和优化将大大改善早期成岩作用的概念和定量模型的基础，有助于实验设计，并扩大用于管理目的的生物地球化学过程的实际现场监测的能力。实时荧光传感器图像提供了一种有效的手段来传达底栖生物地球化学过程的动力学和重要性，并与非专业人员接触。平面光电传感器图像和现场荧光传感器REMOTS系统将作为教育和研究工具被纳入海洋科学研究中心REU暑期计划，这是一个面向现场的本科课程，也将被用作通过新的Sigma Xi科学咖啡馆计划等公共论坛提高对海底过程的一般认识的一种方式。研究生和本科生教育和技术培训将继续与实验室和实地研究密切结合。成果将在国家和国际会议上以及国际科学期刊上公布。

OCE-0526410Diagenetic processes in sedimentary deposits play a central role in the cycling and burial of biogeochemically reactive elements. The activities of marine bottom-dwelling animals dramatically impact early diagenesis, altering material transport and reaction distributions in surface sediments over much of the seafloor. The present research will examine, conceptualize, and quantify specific aspects of these biogenic effects on biogeochemical cycles, and will so within the context of synand autecological characteristics of benthos. Feeding, burrowing, and the irrigation of biogenic structures create complex, time-dependent networks of oxic and anoxic microenvironments. The scaling and macro-geometrical patterns of these microenvironments determines absolute and relative rates of remineralization pathways, microbial abundances and activities, and the coupling between reactions such as nitrification - denitrification or carbonate dissolution - precipitation. Such biogenic heterogeneity is virtually impossible to accurately measure or quantify by traditional methods.IN this project, researchers at the State University of New York at Stony Brook will continue their observational, experimental, and technological development studies of benthic communities and their two-way relationship with sediment chemistry. A set of planar fluorosensors (planar optodes) designed to measure pH, pCO2, and O2 at high resolution (ca. 30 - 50 um) in single images over areas of 100 - 300 cm2 were developed in part during the previous funding period and will be further optimized. A composite sensor will be developed to allow simultaneous measurement of O2, H+, and CO2. These fluorosensors will be used to directly investigate three-dimensional solute distributions produced by functionally different infauna in laboratory microcosms, and in natural communities in situ using a sediment profiling camera modified for use with planar optodes. The effects of both individual and mixtures of functional types will be examined at multiple densities. Remineralization rates around biogenic structures will be quantified and hypotheses regarding scaling - reaction relationships tested. Direct measures of microbial activity around biogenic structures will be guided by the optically sensed patterns. Diffusion-reaction cells designed to simulate the effect of irrigated burrows will be used together with optical sensors to examine transient and pseudo-steady reaction balances and microbial activity as a function of diffusive transport scale for comparison with natural structures of similar scale. Diffusion cell measurements on mucus secretions will be performed to further constrain semipermeable properties, the fractionation of DOC constituents, and metabolic patterns. Additional experiments on decomposition rates of natural interstitial mucus and tube linings will also be carried out. The implications of semi-permeabilty of pore space and anisotropic transport will be incorporated into conceptual and mathematical models. Broader Impacts: The present research will advance predictive, mechanistic-based understanding of interactions between benthic communities and sediment chemistry, their effect on biogeochemical cycles of societal importance, and the fate of pollutants. The further development and optimization of planar fluorosensors for biogeochemical applications will substantially improve the basis for conceptual and quantitative models of early diagenesis, aid experimental design, and extend capacity for practical in situ monitoring of biogeochemical processes for management purposes. Real time fluorosensor images provide an effective means to communicate the dynamics and importance of benthic biogeochemical processes, and to engage non-specialists. Planar optode sensor images and the in situ fluorosensor REMOTS system will be incorporated as educational and research tools in the Marine Sciences Research Center REU summer program, a field-oriented undergraduate course, and will also be used as a way to raise general awareness about benthic processes through public forums such as the new Sigma Xi science cafe program. Graduate and undergraduate education and technical training will continue to be intimately integrated with laboratory and field research. Results will be presented at national and international meetings, and in international scientific journals.