Insights into biogeochemical transformations and fluxes from high-frequency ocean time-series data.

这项研究将检查碳、氮、氧和碘的海洋循环。氧和碳将在拉布拉多海进行研究，在那里，冬季的深层混合创造了氧气、人为二氧化碳和有机碳向海洋内部快速、气候敏感转移的潜力。氮和碘的循环将在新斯科舍省的贝德福德盆地进行研究，这是一个70米深的沿海峡湾，毗邻哈利法克斯。这项研究将基于化学、物理和生物参数的时间序列，这些参数来自：a)拉布拉多海深水地层区域的一个自主的多学科观测站，该观测站是向深海输送氧气和人为二氧化碳的关键区域；b)来自季节分层贝德福德盆地的多学科每周时间序列，该盆地的氮循环受到人类的影响，氮和碘都经历了重大的季节转变。在拉布拉多海（2021年夏季）部署SeaCycler剖面绞车和传感器包，将提供生物光学特性、溶解气体（CO2和O2）、硝酸盐、磷酸盐、温度、盐度和湍流的高分辨率剖面（0-150米，每天1-4次，一年一次），以及浮游动物生物量的估计。SeaCycler将在附近的系泊处与固定深度的pH值、碱度、二氧化碳分压测量同时进行，该系泊处还将配备（由其他研究人员）浮游植物采样器，使物种演代与化学/物理数据相关。HQP将使用新数据以及早期部署的数据来检查：1)通过冬季混合出口到深海的净群落产量的比例（与通过生物碳泵沉降相比）；2)解释春季开花时间的因素；3)季节分层后的有机碳输出效率，基于绿化带上下的养分、碳和氧预算。考虑到有限的交换和可管理的规模，贝德福德盆地具有大型自然中游环境的特点，因此时间序列可以详细检查物种变化以及氮和碘通量的潜在过程。时间序列将为HQP项目提供背景，这些项目将涉及重复的短期实验操作，以测试和完善对化学和微生物介导的转化（例如硝化；碘酸还原）的理解和参数化。在这两个地点，时间序列为HQP的多学科团队提供了一个环境，以开展互补项目。这项研究将提供：(a)利用全面的现场数据，检验自1950年代以来争论不休的关于春季浮游植物大量繁殖的各种假设；(b)了解通过深海混合向深海输送有机碳和氧对气候变化的敏感性；(c)了解对沿海海洋中氮和碘的形态和通量的控制。

The research will examine ocean cycling of carbon, nitrogen, oxygen and iodine. Oxygen and carbon will be studied in the Labrador Sea, where wintertime deep mixing creates potential for rapid, climate-sensitive transfer of oxygen, anthropogenic CO2 and organic carbon to the ocean interior. The cycling of nitrogen and iodine will be studied in Bedford Basin, Nova Scotia, a 70m deep coastal fjord, adjacent to Halifax. The research will be based on time-series of chemical, physical and biological parameters from: a) an autonomous, multidisciplinary observatory in the deepwater formation region of the Labrador Sea which is a key region for delivery of O2 and anthropogenic CO2 to the deep ocean; b) a multidisciplinary, weekly time-series from the seasonally-stratified Bedford Basin, whose nitrogen cycle is impacted by humankind and in which both nitrogen and iodine undergo major seasonal transformation. Deployment of the SeaCycler profiling winch and sensor package in the Labrador Sea (summer 2021), will provide high-resolution profiles (0-150m; 1-4 times per day for a year) of bio-optical properties, dissolved gases (CO2 and O2), nitrate, phosphate, temperature, salinity and turbulence, as well as estimates of zooplankton biomass. The SeaCycler will be operated in parallel with fixed-depth measurement of pH, alkalinity, pCO2 at a nearby mooring which will also be equipped (by other investigators) with a phytoplankton sampler allowing species succession to be related to chemical/physical data. HQP will use the new data as well as data from an earlier deployment to examine: 1) the fraction of net community production exported to the deep ocean by winter mixing (compared to settling via the biological carbon pump); 2) factors that explain the timing of the spring bloom; 3) the organic carbon export efficiency after seasonal stratification, based on nutrient, carbon and oxygen budgets above and below the euphotic zone. Given constrained exchanges and manageable size, Bedford Basin has characteristics of a large natural mesocosm so that time-series allow detailed examination of processes underlying speciation changes as well as fluxes of nitrogen and iodine. The time-series will provide context for the HQP projects which will involve repeated, short-term experimental manipulations to test and refine understanding and parameterization of chemical and microbially-mediated transformations (e.g. nitrification; iodate reduction). In both locations, the time-series provide an environment for multidisciplinary teams of HQP to work on complementary projects. The research will deliver: (a) tests, with comprehensive in-situ data, of diverse hypotheses for initiation of spring phytoplankton blooms, debated since the 1950's; (b) understanding of the sensitivity to climate change of organic carbon and oxygen delivery to the deep ocean via deep-mixing; (c) understanding of controls of nitrogen and iodine speciation and fluxes in the coastal ocean.