BIOGEOCHEMICAL dataset collected during the TONGA cruise

The objective of the TONGA oceanographic expedition was to study the control of productivity and carbon sequestration by micronutrients of shallow hydrothermal origin in the Western Tropical South Pacific (WTSP) Ocean. The 37-day oceanographic survey took place on board the R/V L’Atalante in 2019 between Oct. 31 to Dec. 6 (Nouméa-Nouméa). Over a large area of the WTSP the team acquired numerous results on both the entire water column (up to the sediment) and the atmosphere. Specific task are represented on figure 1: (task 1) to characterize chemically and optically shallow hydrothermal fluids and to compare the source from below (shallow hydrothermal fluids) with the source from above (atmospheric deposition); (task 2) to quantify the dynamical dispersion of the fluids at small and regional scale; (task 3) to investigate the impact of the shallow hydrothermal sources on the biological activity and diversity, and the feedback to the atmosphere via the oceanic emissions of primary and secondary aerosols. (Task 4) to communicate about the campaign (see for example our Tweeter account (https://twitter.com/tongaproject) and the movie (26’) both in French (https://www.youtube.com/watch?v=e5kAd0i6Dck) and English (https://www.youtube.com/watch?v=UeABf-cVR-k). A long west to east (up to the blue waters of the gyre) transect allowed to characterize the different biogeochemical provinces crossed and a focus in the region of the Lau Basin allowed to investigate the impact of shallow hydrothermal sources. A series of short and long stations allowed to fully characterize the stocks and the fluxes in the different provinces. Short-term (up to 10 days) processes studies have been conducted (drifting moorings and minicosms experiments). Part of these results will feed into important modeling work. A fixed mooring line launched at the end of the campaign and recovered in Nov. 2020 as well as the 7 ARGO floats and 20 drifting buoys that were dropped during the campaign provide a broader temporal context of the acquisitions done during the campaign. An important focus of the campaign was the trace metal characterization of the entire water column. For this, TONGA has been labeled by the international program GEOTRACES (https://www.geotraces.org/). The impact on biological communities of fluids is supported by the international IMBER program (https://imber.info/). The TONGA project is also part of the LEFE program (funding by LEFE-CYBER and LEFE-GMMC), the ANR (Appel à projets génériques) and the Fondation A-MIDeX of the Aix-Marseille Université. Scheme of the different tasks of the TONGA project and cruise

TONGA海洋考察的目标是研究热带西南太平洋（Western Tropical South Pacific, WTSP）中浅源热液微营养素对生产力和碳封存的调控作用。2019年10月31日至12月6日期间，考察队乘坐R/V L’Atalante号（努美阿-努美阿航线）开展了为期37天的海洋调查。在WTSP的广阔区域内，团队获取了覆盖整个水柱（直至沉积物）及大气的大量观测结果。具体任务如图1所示：（任务1）对浅源热液流体进行化学与光学表征，并对比下方来源（浅源热液流体）与上方来源（大气沉降）；（任务2）量化流体在小尺度与区域尺度的动态扩散；（任务3）探究浅源热液对生物活性与多样性的影响，以及海洋排放的初级和次级气溶胶对大气的反馈作用；（任务4）开展考察相关的科普宣传（例如可访问我们的Twitter账号（https://twitter.com/tongaproject）及英法双语影片（26分钟）：法语版（https://www.youtube.com/watch?v=e5kAd0i6Dck）、英语版（https://www.youtube.com/watch?v=UeABf-cVR-k））。

一条从西向东延伸至环流蓝水区的长断面，为表征所穿越的不同生物地球化学区域提供了基础；同时，考察重点聚焦劳盆地，以探究浅源热液的影响。一系列短期与长期站位的观测，实现了对不同区域物质存量与通量的全面表征。此外，团队开展了短期（最长10天）过程研究（包括漂流锚系观测与微型生态系统实验）。部分观测结果将为重要的建模工作提供数据支撑。考察结束时投放的固定锚系（2020年11月回收）、7个ARGO浮标及20个漂流浮标，为考察期间的观测数据提供了更广泛的时间背景。

本次考察的核心重点之一是全水柱痕量金属的表征。为此，TONGA被国际GEOTRACES计划（https://www.geotraces.org/）列为标签项目。热液流体对生物群落的影响研究得到了国际IMBER计划（https://imber.info/）的支持。TONGA项目同时隶属于LEFE计划（由LEFE-CYBER与LEFE-GMMC资助）、ANR（通用项目申请）及艾克斯-马赛大学A-MIDeX基金会。TONGA项目与考察的各任务示意图如下。