This dataset presents surface oceanographic measurements collected from 2004 to 2009 along the Patagonian Shelf (35°–55°S) as part of the Patagonian Experiment (PATEX) conducted by the High Latitude Oceanography Group (GOAL-FURG). The measurements include hydrographic variables (temperature, salinity, conductivity, pressure), dissolved oxygen concentration, chlorophyll-a, surface wind speed, and the partial pressure of CO2 in both seawater (pCO2sw) and the atmosphere (pCO2air). Derived variables include density, dissolved oxygen saturation, air-sea CO2 gradient (delta_pCO2), modeled CO₂ fugacity, air–sea O2 and CO2 fluxes derived from multiple gas-exchange parameterizations (Woolf 1997, Woolf 1991, Wanninkhof 1992, Wanninkhof 2014, Liang et al.), and non-thermal and thermal components of O2 fluxes.DO measurements from the sensor were corrected using DO samples obtained with the Winkler method (Winkler, 1888). No correction was applied to the fluorometer data. In addition to the physicochemical variables, the dataset provides a characterization of the phytoplankton community, classified by pigment composition via high-performance liquid chromatography (HPLC; following Zapata et al., 2000) and by microscopic counts. HPLC measurements are available from PATEX 4 onward, whereas earlier cruises include only microscopic abundance and biovolume estimates. Together, these data encompass major functional groups (diatoms, dinoflagellates, cyanobacteria, cryptophytes, green flagellates, and haptophytes), as well as total chlorophyll-a and total biovolume. The dataset supports investigations of air–sea gas exchange, carbon and oxygen cycles, primary productivity, and the ecological dynamics of phytoplankton in the Southwestern Atlantic, contributing to ongoing efforts to quantify the role of coastal and shelf systems in regional and global climate-relevant processes.