The Cape São Tomé Eddy Transect during the ILHAS 3 Research Cruise

<h2><em>Description</em></h2> <p>During the ILHAS 3 expedition, a strong coherent cyclonic mesoscale meander was detected between 22&ordm;S and 24&ordm;S, about 100 km offshore of the Rio de Janeiro State, Brazil. The feature was surveyed with a hydrographic transect between 09 and 11 December 2019 (end of spring) onboard the University of S&atilde;o Paulo's R/V <em>Alpha Crucis</em>.</p> <p>The transect was oriented in the SW-NE direction, roughly following the 2000 m isobath. The ship moved NE, occupying 19 stations. The oceanographic sampling instruments included: a shipboard Acoustic Doppler Current Profiler (ADCP) RDI-75 kHz; a Profiling Natural Fluorometer System (PNF-300); and a Niskin rosette with a payload consisting of Niskin bottles for water sampling, and a Sea-Bird SBE 9 Conductivity-Temperature-Depth profiler (CTD) carrying sensors for temperature (SBE 3plus), conductivity (SBE4), dissolved oxygen (SBE43), and fluorescence (Turner Cyclops) for Chlorophyll-a. Water samples were collected at standard depths for the determination of nitrate, nitrite, phosphate, and silicate using an AutoAnalyzer-3 SEAL Analytical System. Aliquots of 1 L were retrieved, filtered onto Whatmann GF/F filters, and for later Chlorophyll-a measurements with a Tuner Design AU-10 Fluorometer. Flow cytometry was performed with an Attune Nxt Flow Cytometer for pico- and nano-phytoplankton community analyses. Primary production experiments were performed in the euphotic zone at two stations (in the eddy center and the outermost station).</p> <p>&nbsp;</p> <h3><em>Acknowledgments</em></h3> <p><em>The Brazilian Navy, Petrobras (Petr&oacute;leo Brasileiro S.A.), and ANP (Brazilian National Agency of Petroleum, Natural Gas and Biofuels) for facilitating the fieldwork under the Cooperation Terms SIGITEC 2018/00451-6 and 2018/00452-2.</em></p> <p><em>Captain Jos&eacute; Rezende, commanding officer of the R/V Alpha Crucis, and crew, as well as others of the technical staff, undergraduate and graduate students on board, whose assistance was indispensable for data collection.</em></p>