What was sampled: Mangrove sedimentParameter measured and method:1. Organic carbon (Corg), analyzed using elemental analyzer (Eurovector E3000 Elemental Analyzer)2. Total nitrogen (N), analyzed using elemental analyzer (Eurovector E3000 Elemental Analyzer)3. Stable carbon isotope composition (δ13Corg), analyzed using Thermo Finnigan Delta plus mass spectrometer coupled to a Flash EA1112 Elemental Analyzer4. Gamma emitting radionuclides, measured using non-destructive high resolution, low background HPGe gamma spectroscopy (Canberra Inc.)Where was sampled: Central Segara Anakan Lagoon, Central Java, IndonesiaWhen was sampled: Sediment samples were taken in November 2016.How it was sampled: Mangrove sediments were collected using a 1 m long semi-cylindrical auger. Sediments were taken down to 1 m depth, and were sampled in 5 cm interval.