Description: What was sampled: Mangrove sediment Parameter 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 Analyzer 4. Gamma emitting radionuclides, measured using non-destructive high resolution, low background HPGe gamma spectroscopy (Canberra Inc.) Where was sampled: Berau, East Kalimantan, Indonesia When was sampled: Sediment samples were taken in May 2013 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.

Description: What was sampled: Mangrove sediment Parameter 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 Analyzer 4. 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, Indonesia When 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.

Description: This compilation contains data from 18 mangrove sediment cores: organic carbon (Corg), total nitrogen (N) and stable carbon isotope composition (δ13Corg). For 3 cores, gamma emitting radionuclides data are additionally available. The cores were sampled in Segara Anakan Lagoon (Central Java), Berau (East Kalimantan) and Kongsi Island (Thousand Islands Marine National Park, Jakarta), in Indonesia. Sediment samples from Segara Anakan Lagoon and Kongsi Island were taken in October - December 2016. Sediment samples from Berau were taken in May 2013. The mangrove sediment cores were collected using a 1 m long semi-cylindrical auger. Sediments were taken down to 1 m depth, and were sampled in 5 cm intervals.

Description: What was sampled: Mangrove sediment Parameter 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 Analyzer 4. Gamma emitting radionuclides, measured using non-destructive high resolution, low background HPGe gamma spectroscopy (Canberra Inc.) Where was sampled: Eastern Segara Anakan Lagoon, Central Java, Indonesia When was sampled: Sediment samples were taken in December 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.

Description: Mangrove ecosystems are an important natural carbon sink that accumulate and store large amounts of organic carbon (Corg), in particular in the sediment. However, the magnitude of carbon stocks and the rate of carbon accumulation (CAR) vary geographically due to a large variation of local factors. In order to better understand the blue carbon sink of mangrove ecosystems, we measured organic carbon stocks, sources and accumulation rates in three Indonesian mangrove ecosystems with different environmental settings and conditions; (i) a degraded estuarine mangrove forest in the Segara Anakan Lagoon (SAL), Central Java, (ii) an undegraded estuarine mangrove forest in Berau region, East Kalimantan, and (iii) a pristine marine mangrove forest on Kongsi Island, Thousand Islands, Jakarta. In general, Corg stocks were higher in estuarine than in marine mangroves, although a large variation was observed among the estuarine mangroves. The mean total Corg stock in Berau (615 ± 181 Mg C ha−1) is twice as high as that in SAL (298 ± 181 Mg C ha−1). However, the Segara Anakan Lagoon displayed large within-system variation with a much higher Corg stock in the eastern (483 ± 124 Mg C ha−1) than in the central lagoon (167 ± 36 Mg C ha−1). The predominant accumulation of autochthonous mangrove organic matter likely contributed to the higher Corg stocks in Berau and the eastern SAL. Interestingly, the CAR distribution pattern in SAL is opposite to that of its Corg stocks. The central SAL that receives high sediment inputs from the hinterland has a much higher CAR than the eastern SAL (658 ± 311 g C m−2 yr−1 and 194 ± 46 g C m−2 yr−1, respectively), while Berau has one of the highest CAR (1722 ± 183 g C m−2 yr−1) ever measured. It appears that these large differences are driven by the environmental setting and conditions, mainly sediment dynamics and hydrodynamics, landform, and vegetation conditions. It is inferred that quantifying carbon accumulation in sediments is a useful tool in estimating the present-day carbon storage of mangrove ecosystems. This is a precondition for taking measures under REDD+ (Reducing Emissions from Deforestation and Forest Degradation and the role of conservation, sustainable management of forests and enhancement of forest carbon stocks in developing countries) schemes.