Collaborative Research: Dissolved Organic Matter Degradation in Filtering Shelf Sands

了解离散碳池的大小和周转时间对于准确计算和模拟全球海洋碳动态至关重要。海洋溶解有机碳库(DOM)是地球上最大的可交换碳库之一，其产生或沉没的条件可以强烈影响海洋和大气二氧化碳之间的平衡，或改变海洋沉积物中碳的储存。大陆架充当大量DOM的汇，这些DOM通过河流和陆地径流进入海洋。尽管陆源DOM的很大一部分是难熔的，但它不会在陆架和海洋中积累，这一过程尚未得到很好的了解，但对全球碳循环至关重要。在这项研究中，佛罗里达州立大学和北卡罗来纳大学教堂山分校的PI假设，富含DOM的沿海水被底流和波浪泵送到可渗透陆架沉积物的表层，迫使DOM通过具有较大反应表面积和不同生物地球化学反应区域的生物催化转化器。他们之前由美国国家科学基金会资助的调查显示，沉积物和水柱之间的酶水解率平均增加了200倍。拟议研究的具体目标是：1)定量测定过滤的墨西哥湾沙子和上覆水中DOM的降解；2)评估孔隙流速、温度、氧气浓度和光照对DOM分解率的影响；3)FT-ICR-MS表征沉积物通道引起的DOM组成变化；4)量化具有代谢活性的原核生物的丰度，并建立DOM代谢和微生物群落系统发育组成之间的直接联系；5)将结果整合到一个经验模型中，该模型将DOM降解率与孔隙水速度、温度、氧气和光照定量地联系起来。更广泛的影响包括开发一个项目网站、公开讲座、向公众媒体发布新闻以及向位于研究地点的海洋科学联盟海洋实验室的访问者分发信息材料。将通过本科生积极参与实地和实验室研究来加强人力资源开发，四名研究生将根据这项研究的各个方面撰写论文。该项目将通过来自德国、荷兰和巴拿马的研究人员的积极参与来提高国际知名度和合作。

Knowledge of the sizes and turnover times of discrete pools of carbon is essential for accurate accounting and modeling of global ocean carbon dynamics. Production or sink terms of the oceanic pool of dissolved organic carbon (DOM), one of the largest exchangeable carbon reservoirs on earth, can strongly impact the balance between oceanic and atmospheric CO2 or change the storage of carbon in marine deposits. The continental shelf acts as sink for large quantities of DOM that reach the sea through rivers and runoff from land. Although a large fraction of the terrigenous DOM is refractory, it does not accumulate in the shelf and oceans, a process that is not well understood but is critical for the global cycles of carbon. In this research, PIs from Florida State University and University of North Carolina at Chapel Hill hypothesize that DOM laden coastal water is pumped through the surface layers of permeable shelf sediments by bottom currents and waves, forcing DOM through a biocatalytical converter with large reactive surface area and different biogeochemical reaction zones. Their prior NSF funded investigations showed an average 200-fold increase in enzymatic hydrolysis rates between sediments and water column. The specific objectives of the proposed research are 1) quantification of DOM degradation in filtering Gulf of Mexico sands and overlying water 2) assessment of the influences of pore flow velocity, temperature, oxygen concentration and light on DOM decomposition rates, 3) FT-ICR-MS characterization of DOM compositional changes caused by sediment passage and 4) quantification of the abundance of metabolically active prokaryotes and establishment of a direct linkage between DOM metabolism and the phylogenetic composition of microbial communities, 5) integration of the results into an empirical model that quantitatively relates DOM degradation rates to pore water velocity, temperature, oxygen and light. The broader impacts include development of a project web site, public lectures, news releases to the public media and information materials distributed to visitors of the FSU marine lab located at the study site. Human resource development will be enhanced through active participation of undergraduate students in field and laboratory research, and four graduate students will develop their theses based on aspects of this research. The project will enhance international visibility and collaboration through active participation of researchers from Germany, the Netherlands, and Panama.