Oxygen profiles in estuarine sediments exposed to acidification

We collected twelve sediment cores from two sites in Waquoit Bay (Massachusetts, USA): Metoxit Point (MP) in September 2021 and from Sage Lot Pond (SLP) in October of 2021. We collected the cores using a pull corer which maintains the vertical structure of the sediment cores and preserves the delicate sediment-water interface (Foster and Fulweiler 2019). We transported the cores back to Boston University within 7 hours of collection and placed them in an environmental chamber set to 29 (±1) °C. To better understand the impact of pH of sediment biogeochemical cycling we conducted continuous flow through incubations with treatments representing control (pH 8.0), moderate (pH 7.3) and extreme pH conditions (pH 6.3). Site water was treated with ambient air and CO2 to reach appropriate pH conditions. We conducted triplicate sediment O2 profiles within each core before and after incubations to measure the treatment effects of pH on O2 conditions within sediments. Using a standard 100-µm O2 microelectrode (100 µm diameter) mounted on a motorized micromanipulator profiler and the Sensor Trace Pro v. 3.0.6 control software (Unisense, Aarhus, Denmark) we measured O2 concentrations at 250 µm increments down to 1 cm. All calibrations and measurements were done in the lab at ambient air temperature. Email questions and comments to [e-mail] <strong>Sampling Sites:</strong> Metoxit Point = 41° 34’ 8.04” N 70° 31’ 17.76” W Sage Lot Pond = 41° 34’ 8.04” N 70° 30’ 30.20” W <strong>Profiling Information:</strong> Experiment Type = For each station we conducted two incubations. The first incubation conducted was the Extreme treatment (pH 6.3) which included 3 control cores and 3 cores acidified to a pH of 6.3. The second experiment conducted was the moderate treatment (pH 7.3). Treatment = The treatment each cores were exposed to: Control = pH 8.0 pH 6.3 = Extreme pH 7.3 = Moderate Incubation_Time = When profiles was collected either before incubation (Pre-Incubation) or after incubations (Post-Incubation). Depth_mm = sampling depth in millimeters Oxygen = oxygen concentration (µmol L-1) SE = standard error of triplicate oxygen measurements Group = detailed descritpion of oxygen profile <strong>Acknowledgements:</strong> We would like to thank the Waquoit Bay National Estuarine Research Reserve (WBNERR) for their support of our research. Sediment cores for this study were collected using WBNERR boats. We are particularly grateful for Dr. Megan Tyrrell and Tonna-Marie Rogers who were instrumental in helping us carry out fieldwork and for making sure we had all the resources necessary for a successful field day. We would also like to thank members of the Fulweiler Lab, Alia Al-Haj, Amanda Vieillard, Catherine Mahoney, Kwetzpallin Mexika, Melissa Ederington Hagy, Nia Bartolucci, Paulina Azzu, and Ryan Shipley for their help with sample prep, field work and experiments. <strong>References</strong> Foster SQ, Fulweiler RW (2019) Estuarine Sediments Exhibit Dynamic and Variable Biogeochemical Responses to Hypoxia. J Geophys Res Biogeosciences 124:737–758. https://doi.org/10.1029/2018JG004663 <strong>Funding</strong> This work was funded by MIT SeaGrant through grants to RWF and by the NOAA Margaret A. Davidson Graduate Fellowship awarded to CIM. CIM received additional support from the Mount Holyoke Alumnae Fellowship, the Warren-McLeod Graduate Fellowship from the Boston University Marine Program, and from Boston University’s Department of Earth &amp; Environment.

本研究于2021年9月从美国马萨诸塞州瓦科伊特湾（Waquoit Bay）的梅托克西特点（Metoxit Point, MP），以及2021年10月从萨奇洛特池塘（Sage Lot Pond, SLP）两个采样点，共采集了12根沉积物柱芯。采样采用活塞式沉积物采芯器（pull corer）进行，该设备可保留沉积物柱芯的垂直结构，并完整保存脆弱的沉积物-水界面（Foster与Fulweiler, 2019）。采样完成后7小时内将柱芯运回波士顿大学，并置于设定温度为29(±1)℃的环境培养箱中保存。为探究pH对沉积物生物地球化学循环的影响，本研究设置了对照（pH 8.0）、中度（pH 7.3）与极端（pH 6.3）三种pH处理组，开展连续流培养实验。利用通入常压空气与二氧化碳的方式调节原位海水的pH至目标值。分别在培养实验前后，对每根柱芯进行三次重复的沉积物氧气剖面测量，以评估pH处理对沉积物内部氧气环境的影响。实验采用安装于电动微操纵剖面仪上的标准100 µm（直径）氧气微电极，搭配Sensor Trace Pro v3.0.6控制软件（丹麦奥胡斯Unisense公司出品），以250 µm的步长向下至1 cm深度测量氧气浓度。所有校准与测量操作均在实验室室温条件下完成。如有疑问或建议，请致邮至[e-mail]。<strong>采样位点：</strong>梅托克西特点：北纬41°34′8.04″，西经70°31′17.76″；萨奇洛特池塘：北纬41°34′8.04″，西经70°30′30.20″<strong>剖面测量信息：</strong><strong>实验类型：</strong>每个采样点均开展两次培养实验。首次为极端pH处理组（pH 6.3），包含3根对照柱芯与3根酸化至pH 6.3的柱芯；第二次为中度pH处理组（pH 7.3）。<strong>处理分组：</strong>各柱芯所接受的处理如下：对照组：pH 8.0；极端pH组：pH 6.3；中度pH组：pH 7.3<strong>培养时间：</strong>剖面测量的采样时机分为培养前（预培养阶段）与培养后（后培养阶段）<strong>字段说明：</strong>Depth_mm：采样深度，单位为毫米；Oxygen：氧气浓度，单位为µmol L⁻¹；SE：三次氧气测量的标准误；Group：氧气剖面的详细描述<strong>致谢：</strong>本研究感谢瓦科伊特湾国家河口研究保护区（Waquoit Bay National Estuarine Research Reserve, WBNERR）提供的研究支持，本次沉积物柱芯采样使用了WBNERR的工作船。特别感谢梅根·蒂雷尔博士（Dr. Megan Tyrrell）与唐娜-玛丽·罗杰斯（Tonna-Marie Rogers），他们为野外采样工作提供了关键协助，并保障了野外作业所需的全部资源。同时感谢Fulweiler实验室的成员Alia Al-Haj、Amanda Vieillard、Catherine Mahoney、Kwetzpallin Mexika、Melissa Ederington Hagy、Nia Bartolucci、Paulina Azzu及Ryan Shipley，他们在样品制备、野外工作与实验开展过程中提供了大量帮助。<strong>参考文献：</strong>Foster SQ, Fulweiler RW (2019) 河口沉积物对低氧环境表现出动态且多变的生物地球化学响应. 《地球物理研究杂志：生物地球科学》，124卷：737–758. https://doi.org/10.1029/2018JG004663<strong>资助信息：</strong>本研究由麻省理工学院海洋资助项目（MIT SeaGrant）向RWF提供的资助，以及美国国家海洋和大气管理局（NOAA）玛格丽特·A·戴维森研究生奖学金（Margaret A. Davidson Graduate Fellowship）资助CIM。CIM同时获得了曼荷莲学院校友奖学金（Mount Holyoke Alumnae Fellowship）、波士顿大学海洋项目沃伦-麦克劳德研究生奖学金（Warren-McLeod Graduate Fellowship），以及波士顿大学地球与环境系的资助。