Chlorophyll a and macro-nutrient concentrations and photosynthetically active radiation during the training vessel Umitaka-maru cruise of the 60th Japanese Antarctic Research Expedition in January 2019

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 the another monitoring program. This report is the latest data collected during the T/V Umitaka-maru cruise in 2018/19 season.

叶绿素a浓度是浮游植物生物量最常用的指示指标，其基础调控因子为大量营养素与光照强度。因此长期监测这些参数，可为我们提供气候变化背景下生态系统变化的基础信息。作为日本南极考察队（JARE, Japanese Antarctic Research Expedition）监测计划的一部分，“富士”号（Fuji）与“白濑”号（Shirase）破冰船自第14次考察（1972/73航次）起开始测定叶绿素a浓度，自第7次考察（1965/66航次）起开始测定大量营养素（硝酸盐、亚硝酸盐、磷酸盐与硅酸）浓度。同样的监测工作也由东京海洋大学（Tokyo University of Marine Science and Technology）的训练船“海鹰丸”号（T/V Umitaka-maru）自第55次考察（2013/14航次）起开展。“海鹰丸”号的年度航线基本一致：从弗里曼特尔（Fremantle）起航，沿110°E经线向南航行至冰缘带（约南纬65°）后返航至霍巴特（Hobart），覆盖南大洋从亚热带到极地的各类水域。本次航行期间，通过船载泵系统采集水样以测定叶绿素a与大量营养素浓度，采样频率为每日两次；光合有效辐射则通过安装在船舶驾驶桥楼甲板上的传感器持续监测。沿110°E经线共设置6个站位开展叶绿素a浓度的垂直水样采集，不过上述站位的大量营养素浓度数据来自另一项监测计划。本报告收录的为2018/19航次“海鹰丸”号航行期间采集的最新数据集。