Size-fractionated chlorophyll a (>20 µm and <20 µm) in Reloncaví Sound (Chile) during the austral spring–summer 2023–2024

This dataset reports size-fractionated chlorophyll-a concentrations (>20 µm and <20 µm; µg L⁻¹) measured in the Reloncaví Sound during the austral spring 2023–summer 2024 transition. Samples were collected at four stations from the surface and from the fluorescence maximum depth to assess phytoplankton biomass distribution. Chlorophyll-a was extracted in 90% acetone and quantified fluorometrically following Parsons et al. (1984).