Chlorophyll a and macro-nutrient concentrations and photosynthetically active radiation during the training vessel Umitaka-maru cruise of the 59th Japanese Antarctic Research Expedition in January 2018

Chlorophyll a concentration is the most common indicator of phytoplankton biomass, fundamentally regulated by macro-nutrients and light intensity. Therefore, long term monitoring of these parameters gives us basic information on ecosystem changes with climate changes. As part of the monitoring programs of the Japanese Antarctic Research Expedition (JARE), chlorophyll a concentration and macro-nutrients (nitrate, nitrite, phosphate and silicic acid) have been measured on board icebreakers Fuji and Shirase since JARE-14 (1972/73 season) and JARE-7 (1965/66 season), respectively. The same monitoring has also been conducted during the cruise of the training vessel (T/V) Umitaka-maru, Tokyo University of Marine Science and Technology since JARE-55 (2013/14 season). The course of the Umitaka-maru is almost same every year; leave from Fremantle, goes down to ice edge (ca. 65S) along 110E meridian and back to Hobart, covering sub-tropical to polar waters in the Southern Ocean. During the cruise, water sampling from underway pump for chlorophyll a and macro-nutrient concentrations were obtained twice a day, and photosynthetically active radiation was continuously measured by a sensor mounted on the navigation bridge deck of the ship. The vertical water sampling for chlorophyll a concentration was conducted at 6 station along 110E meridian, although concentration of macro-nutrients at the same stations were determined by another monitoring program. This report is the latest data collected during the T/V Umitaka-maru cruise in 2017/18 season.叶绿素a浓度（Chlorophyll a concentration）是表征浮游植物生物量最常用的指标，其基础调控机制受大量营养素与光照强度共同驱动。长期监测此类参数，可为我们揭示气候变化背景下的生态系统变化提供核心基础数据。作为日本南极调查队（Japanese Antarctic Research Expedition, JARE）监测计划的组成部分，叶绿素a浓度与大量营养素（硝酸盐、亚硝酸盐、磷酸盐及硅酸）的测定工作，分别自第14次JARE（1972/73航次）与第7次JARE（1965/66航次）起，便在富士号（Fuji）与白濑号（Shirase）破冰船上持续开展。 东京海洋大学（Tokyo University of Marine Science and Technology）所属训练船（T/V）海鹰丸（Umitaka-maru）自第55次JARE（2013/14航次）起，也加入了同类监测工作。海鹰丸的年度航线基本固定：从弗里曼特尔（Fremantle）起航，沿110°E经线南下至南大洋冰缘（约南纬65°），随后返航至霍巴特（Hobart），途经从亚热带到极地的各类南大洋水域。 航次执行期间，研究人员每日两次通过走航采水泵采集水样，用于测定叶绿素a浓度与大量营养素浓度；同时通过安装在船舶驾驶甲板上的传感器，持续监测光合有效辐射（photosynthetically active radiation）。此外，研究团队沿110°E经线的6个站位开展了叶绿素a浓度的垂直水样采集，尽管上述站位的大量营养素浓度数据由另一项独立监测计划完成测定。 本报告收录了2017/18航次期间，T/V海鹰丸（Umitaka-maru）科考航次采集的最新观测数据集。