Organic Carbon Oxidation and Iron Remobilization by West Antarctic Shelf Sediments

总声明：南极半岛以西的大陆架地区最近经历了戏剧性的变化和生态系统的变化，生活在海底沉积物中或以海底沉积物为食的生物群落正受到来自北方的物种入侵的影响。以前对这些沉积物的研究表明，这个群落消耗的区域生产力可能比之前估计的要多得多，这表明沉积物是这个生态系统中丰富而重要的组成部分，可能是一个发生戏剧性变化的成熟因素。此外，在更丰富的沉积物条件下，铁被动员并释放回水柱。由于这一生态系统的生产力被认为受到铁的可获得性的限制，从这些沉积物中增加铁的释放速度可能会刺激生产力，并促进整个生态系统的更大变化。在这项研究中，将对陆架地区的各种地点进行采样，以准确地评估沉积物在消耗生态系统生产力方面的作用，并估计目前沉积物中铁的释放水平。该项目将提供一套沉积物结果的基线，以便更全面地了解南极西部大陆架生态系统，以便与水柱测量结果进行比较，并评估这一重要生态系统的基本工作原理。这一点特别重要，因为高纬度系统可能容易受到气候波动的影响。研究生和本科生都将接受培训。将在科学会议、其他大学和外展活动中发表演讲。一个项目网站将向公众介绍关键成果，并解释这一新信息如何增进对南极生态系统的了解。项目技术简介：为了确定沉积物在西南极陆架生态系统中的作用，该项目将确定帕尔默长期生态系统研究(LTER)研究区域内不同地点的沉积物有机质氧化速率。为了估计沉积物中铁和锰的释放速率，将对这些地点进行采样，以获得这些金属在孔隙水和重要矿物相中的浓度的详细垂直分布。由于沉积物采样将在LTER现场进行，因此沉积物数据可以与LTER丰富的生产力数据集相关联。具体而言，该项目：a)将确定南极半岛以西陆架沉积物的耗氧速率、有机碳氧化速率、养分释放速率和铁迁移速率；b)将调查沉积物中成岩反应的垂直分布；c)将评估这些沉积速率的区域重要性。沉积物岩心将被用来确定沉积物-水中的溶解氧、总二氧化碳、营养物质的通量，以及这些溶解化合物以及孔隙水中的铁和锰的垂直分布。还将确定总体沉积物的孔隙度、有机碳和氮含量、碳酸盐含量、生物硅含量以及多种固相铁、锰和硫物种的性质。这些测量将可以确定总有机碳的氧化和反硝化速率，以及每个站点的有氧和无氧呼吸的比例。沉积物成岩模拟将有机质氧化过程与金属活化过程联系起来。孔隙水和固相铁、锰分布将被用来模拟这些沉积物中的铁成岩作用，并估计从沉积物到上覆水的铁通量。最后，将沉积物过程的总体区域平均和分布与季节平均的叶绿素生物量和生产力的分布进行比较。

General Statement: The continental shelf region west of the Antarctic Peninsula has recently undergone dramatic changes and ecosystem shifts, and the community of organisms that live in, or feed off, the sea floor sediments is being impacted by species invasions from the north. Previous studies of these sediments indicate that this community may consume much more of the regional productivity than previously estimated, suggesting that sediments are a rich and important component of this ecosystem and one that may be ripe for dramatic change. Furthermore, under richer sediment conditions, iron is mobilized and released back to the water column. Since productivity in this ecosystem is thought to be limited by the availability of iron, increased rates of iron release from these sediments could stimulate productivity and promote greater overall ecosystem change. In this research, a variety of sites across the shelf region will be sampled to accurately evaluate the role of sediments in consuming ecosystem productivity and to estimate the current level of iron release from the sediments. This project will provide a baseline set of sediment results that will present a more complete picture of the west Antarctic shelf ecosystem, will allow for comparison with water column measurements and for evaluation of the fundamental workings of this important ecosystem. This is particularly important since high latitude systems may be vulnerable to the effects of climate fluctuations. Both graduate and undergraduate students will be trained. Presentations will be made at scientific meetings, at other universities, and at outreach events. A project web site will present key results to the public and explain how this new information improves understanding of Antarctic ecosystems. Technical Description of Project: In order to determine the role of sediments within the west Antarctic shelf ecosystem, this project will determine the rates of sediment organic matter oxidation at a variety of sites across the Palmer Long Term Ecosystem Research (LTER) study region. To estimate the rates of release of iron and manganese from the sediments, these same sites will be sampled for detailed vertical distributions of the concentrations of these metals both in the porewaters and in important mineral phases. Since sediment sampling will be done at LTER sites, the sediment data can be correlated with the rich productivity data set from the LTER. In detail, the project: a) will determine the rates of oxygen consumption, organic carbon oxidation, nutrient release, and iron mobilization by shelf sediments west of the Antarctic Peninsula; b) will investigate the vertical distribution of diagenetic reactions within the sediments; and c) will assess the regional importance of these sediment rates. Sediment cores will be used to determine sediment-water fluxes of dissolved oxygen, total carbon dioxide, nutrients, and the vertical distributions of these dissolved compounds, as well as iron and manganese in the pore waters. Bulk sediment properties of porosity, organic carbon and nitrogen content, carbonate content, biogenic silica content, and multiple species of solid-phase iron, manganese, and sulfur species will also be determined. These measurements will allow determination of total organic carbon oxidation and denitrification rates, and the proportion of aerobic versus anaerobic respiration at each site. Sediment diagenetic modeling will link the processes of organic matter oxidation to metal mobilization. Pore water and solid phase iron and manganese distributions will be used to model iron diagenesis in these sediments and to estimate the iron flux from the sediments to the overlying waters. Finally, the overall regional average and distribution of the sediment processes will be compared with the distributions of seasonally averaged chlorophyll biomass and productivity.