This dataset contains blue carbon data from monospecific Posidonia oceanica meadows in the South Aegean Sea, including the Saronikos Gulf, the Cyclades Archipelago, the Dodecanese Archipelago and Crete Island. The dataset includes information from 42 sampling sites and 123 sediment cores collected between 2013 and 2023. The file provides sampling-site information, geographic coordinates, water depth, sampling year, sediment-core characteristics, core compaction, slicing resolution and laboratory processing methods. It also includes mean values for sedimen...