Seamounts generate efficient active transport loops to nourish the twilight ecosystem

Seamounts are ecological oases nurturing abundant fisheries resources and epibenthic megafauna in the vast oligotrophic ocean. Despite their significance, the formation mechanisms underlying these seamount ecological oases remain uncertain. To shed light on this phenomenon, this study conducted interdisciplinary in-situ observations focusing on a shallow seamount in the oligotrophic ocean. In this dataset, we report high-resolution hydrographic and biochemical observational data from both sectional observations and time-series stations observations., Xianbei Seamount is located in the central SCS basin and is an isolated and steep shallow seamount with a summit elevation of 208 m. The transverse section of the seamount is roughly elliptical, with a long axis of about 60 km and a short axis of 40 km. Field observations were conducted onboard the R/V ShenKuo from 14–24 September 2021, and a section parallel to the flow direction was designed to conduct comprehensive field observations. Besides, four time-series stations stretched about 25 h with an interval of 4 h, located at the upstream slope, summit, downstream slope, and downstream bottom. The temperature, salinity, depth, fluorescence, and nitrate were measured using a Seabird 911 plus CTD sensor (frequency, 24 Hz) equipped with a fluorometer and Seabird Deep-Suna (1 Hz). The Photosynthetically active radiation (PAR) was measured with a PAR sensor. The current and particle size spectrum were derived from an RDI 300 kHz LADCP and Hydroptic Underwater Version Profiler 5 (UVP5, maxi..., , # **Date from: Seamounts Generate Efficient Active Transport Loops to Nourish the Twilight Ecosystem**

Seamounts are ecological oases nurturing abundant fisheries resources and epibenthic megafauna in the vast oligotrophic ocean. Despite their significance, the formation mechanisms underlying these seamount ecological oases remain uncertain. To shed light on this phenomenon, this study conducted interdisciplinary *in-situ* observations focusing on a shallow seamount in the oligotrophic ocean. In this dataset, we report high-resolution hydrographic and biochemical observational data from both sectional observations and time-series stations observations.

**Description of the data and file structure**

**File Structure**

We have submitted our raw data including the **Cross-section observational data** (1. Sectional_data.xlsx), **Time-series observational data** (2. Timeseries \_data.xlsx), and **UVP observational data** (3. Particle_and \_Zooplankton_data_UVP.xlsx).

**1) Cross-section ...