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

沉积矿床的成岩过程在生物地球化学活性元素的旋回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面沉积物中的物质运输和反应分布。本研究将在底栖生物的符号和生态特征的背景下，对这些生物成因对生物地球化学循环的影响的具体方面进行检验、概念化和量化。生物结构的取食、挖洞和灌溉创造了复杂的、随时间变化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的绝对和相对速率、微生物丰度和活性，以及硝化-反硝化或碳酸盐溶解-沉淀等反应之间的耦合。这种生物多样性实际上是不可能用传统方法精确测量或量化的。在这个项目中，纽约州立大学石溪分校的研究人员将继续对底栖生物群落及其与沉积物化学的双向关系进行观察、实验和技术开发研究。一组平面荧光传感器（平面光电器件）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）在单幅图像中测量pH， pCO2和O2，部分在上一个资助期间开发，并将进一步优化。将开发一种复合传感器，允许同时测量O2， H+和CO2。这些荧光传感器将用于直接研究实验室微观环境中功能不同的动物产生的三维溶质分布，以及使用改进的平面光电器件使用的沉积物剖面相机在原位的自然群落中。将在多个密度下检查单个功能类型和混合功能类型的影响。将量化生物成因结构周围的再矿化率，并测试有关结垢反应关系的假设。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。为模拟灌溉洞穴效应而设计的扩散反应细胞将与光学传感器一起使用，以检测瞬态和准稳态反应平衡以及微生物活性作为扩散传输尺度的函数，并与类似尺度的自然结构进行比较。将对黏液分泌物进行扩散池测量，以进一步限制半透性、DOC成分的分离和代谢模式。此外，还将进行有关天然间质粘液和管壁分解率的实验。孔隙空间半渗透性和各向异性输运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相互作用的预测，基于机械的理解，它们对社会重要性的生物地球化学循环的影响，以及污染物的命运。用于生物地球化学应用的平面荧光传感器的进一步发展和优化将大大改善早期成岩作用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态和重要性，并吸引非专业人士。平面光电传感器图像和原位荧光传感器REMOTS系统将作为教育和研究工具纳入海洋科学研究中心REU暑期课程，这是一门面向野外的本科课程，也将通过公共论坛（如新的Sigma Xi科学咖啡馆项目）提高人们对底栖生物过程的普遍认识。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。研究结果将在国家和国际会议上以及国际科学期刊上发表。

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.