Chlorophyll-a concentrations from research cruises for the Northern Gulf of Alaska (NGA) LTER site, 2018-2022

This dataset consists of chlorophyll-a concentrations obtained during NGA-LTER research cruises conducted in the Gulf of Alaska during spring, summer and fall, starting in 2018. The data were collected to determine whether chlorophyll-a concentration varies with time (season), location and depth. Included in this dataset are concentrations broken down by size fraction: <20 µm, >20 µm, and total (all as µg/L), as well as the total amount of phaeopigments (µg/L), the fraction of the chlorophyll >20 µm, and integrated chlorophyll. Chlorophyll concentrations were measured in the upper 75 meters of the water column. Excel spreadsheets were converted to CSV files for preservation. These data are part of the Northern Gulf of Alaska Long Term Ecological Research (NGA LTER) program. The LTER program is a National Science Foundation–funded network of 28 sites nationwide that focus on the influence of long-term and large-scale phenomenon on ecosystems. Additional funding for sampling is provided by the North Pacific Research Board (NPRB), the Alaska Ocean Observing System (AOOS), and the Exxon Valdez Oil Spill Trustee Council (EVOS) via the Gulf Watch Alaska program.

本数据集涵盖2018年起在阿拉斯加湾春、夏、秋三季开展的北阿拉斯加湾长期生态研究（NGA-LTER）航次所获取的叶绿素a浓度数据。本次数据采集的核心目标为探究叶绿素a浓度是否随时间（季节）、采样站位及水深发生变化。

数据集包含按粒径分级的叶绿素a浓度：<20 µm、>20 µm 及总浓度（单位均为µg/L），此外还涵盖总脱镁色素浓度（µg/L）、>20 µm 级叶绿素占比，以及积分叶绿素含量。所有叶绿素浓度数据均采集自水柱上层75米范围内。

原始Excel表格已转换为CSV文件以实现长期保存。本数据集隶属于北阿拉斯加湾长期生态研究（NGA-LTER）计划，该计划是由美国国家科学基金会（National Science Foundation）资助的全国性生态研究网络，共包含28个观测站点，聚焦长期与大尺度现象对生态系统的影响。

本次采样工作还获得了北太平洋研究委员会（North Pacific Research Board，NPRB）、阿拉斯加海洋观测系统（Alaska Ocean Observing System，AOOS）以及埃克森·瓦尔迪兹溢油赔偿委员会（Exxon Valdez Oil Spill Trustee Council，EVOS）通过海湾观察阿拉斯加项目提供的额外资金支持。