Microscale profiles of oxygen, pH and temperature through the sea surface microlayer in a mesocosm experiment during an algal bloom@en

The sea surface microlayer (SML) is the boundary layer on top of all oceans and is crucial for all exchange processes between the ocean and atmosphere. This less than 1 mm thick layer is heavily influenced by biological processes and events like algal blooms. To quantify the influence of an algal bloom in a controlled environment, we conducted a mesocosm study at the Sea sURface Facility (SURF) of the Institute for Chemistry and Biology of the Marine Environment (ICBM) in Wilhelmshaven, Germany (53.5148 °N, 8.1463°E). SURF is an 8.5 m long, 2 m wide and 1 m deep water basin, which can directly be filled with seawater from the Jade Bay, North Sea. The facility is equipped with a retractable roof, pumps for water circulation and dedicated mounts for multiple sensor systems. The mesocosm experiment was conducted from 18 May to 16 June 2023 as part of the project BASS (Biogeochemical processes and Air-sea exchange in the Sea-Surface microlayer). SURF was filled with seawater a few days before the start of the experiment (water depth 0.7 m). The water was then filtered and the surface skimmed to remove initial pollution. To prevent particle and microbial sedimentation during the experiment, the pumps operated at low speed to maintain gentle mixing of the water column. The roof of SURF was closed during the night, while it was open during the day except when it rained. To induce an algal bloom, a mix of nutrients (nitrogen, phosphorus and silicate) was added on 26 May, 30 May and 01 June. Based on the chlorophyll measurements which show the development of the bloom, three phases of the experiment were determined: the pre-bloom phase (18 May to 26 May), the bloom phase (27 May to 04 June) and the post-bloom phase (05 June to 16 June). Several physical, chemical and biological parameters were measured, which will be published in other datasets. […]海面微层（sea surface microlayer, SML）是覆盖全球海洋的边界层，对海洋与大气间的所有物质交换过程至关重要。该厚度不足1毫米的水层深受生物过程及藻华等生态事件的影响。为量化受控环境中藻华的影响效应，我们于德国威廉港（Wilhelmshaven）的海洋环境化学与生物学研究所（Institute for Chemistry and Biology of the Marine Environment, ICBM）海面设施（Sea sURface Facility, SURF）开展了中型实验生态系统（mesocosm）研究，实验点位坐标为53.5148°N，8.1463°E。SURF为长8.5米、宽2米、深1米的水体水槽，可直接取用北亚德湾（Jade Bay）的北海海水进行灌注。该设施配备可伸缩屋顶、水循环泵以及多套传感器系统的专用安装基座。本次中型实验生态系统实验于2023年5月18日至6月16日开展，隶属于BASS项目——《海面微层生物地球化学过程与海-气交换》（Biogeochemical processes and Air-sea exchange in the Sea-Surface microlayer）。实验启动前数日，我们向SURF灌注海水（水深0.7米），随后对水体进行过滤并刮除表层以去除初始污染物。为避免实验过程中颗粒物与微生物发生沉降，水泵以低速运行以维持水柱的温和混合状态。SURF的屋顶在夜间闭合，日间保持开放，仅在降雨时关闭。为诱导藻华发生，我们分别于5月26日、5月30日及6月1日添加了由氮、磷、硅酸盐组成的混合营养盐。基于表征藻华发展进程的叶绿素测量结果，我们将本次实验划分为三个阶段：藻华前期（5月18日至5月26日）、藻华期（5月27日至6月4日）以及藻华后期（6月5日至6月16日）。本次实验测定了多项物理、化学与生物学参数，相关数据将在其他数据集中公开发表。[…]