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

这项研究将研究海洋中碳、氮、氧和碘的循环。氧和碳将在拉布拉多海进行研究，那里冬季的深度混合为氧气、人为二氧化碳和有机碳快速、气候敏感地转移到海洋内陆创造了可能性。氮和碘的循环将在新斯科舍省的贝德福德盆地进行研究，新斯科舍省是一个70米深的沿海峡湾，毗邻哈利法克斯。这项研究将基于下列化学、物理和生物参数的时间序列：a)拉布拉多海深水地层区域的一个多学科自主观测站，该区域是向深海输送O2和人为二氧化碳的关键区域；b)贝德福德盆地季节性分层的每周多学科时间序列，其氮循环受到人类的影响，氮和碘都经历了重大的季节性变化。在拉布拉多海(2021年夏季)部署SeaCycler剖面绞车和传感器组件，将提供生物光学性质、溶解气体(二氧化碳和O2)、硝酸盐、磷酸盐、温度、盐度和湍流的高分辨率剖面(0-150米；一年中每天1-4次)，以及浮游动物生物量的估计。SeaCycler将与在附近系泊处对pH、碱度、二氧化碳进行固定深度测量并行操作，该系泊设备还将配备(由其他调查人员)浮游植物采样器，使物种演替与化学/物理数据有关。HQP将使用新的数据以及来自早期部署的数据来检查：1)冬季混合输出到深海的净群落生产的比例(与通过生物碳泵沉淀相比)；2)解释春季水华时间的因素；3)季节性层结后的有机碳输出效率，基于真光带上下的营养、碳和氧收支。考虑到有限的交换和可管理的大小，贝德福德盆地具有大型天然中生态系统的特征，因此时间序列允许详细检查物种形成变化的潜在过程以及氮和碘的通量。时间序列将为HQP项目提供背景，该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(例如硝化作用；碘酸盐还原)的理解和参数化。在这两个地点，时间序列为总部基地的多学科团队提供了一个环境，以开展互补的项目。这项研究将取得成果：(A)用全面的现场数据测试自1950年《S》以来一直争论的关于春季浮游植物大量繁殖的各种假说；(B)了解通过深层混合向深海输送有机碳和有机氧对气候变化的敏感性；(C)了解对沿海海洋氮和碘形态及通量的控制。

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.