ANALYSIS OF CARBON STOCK IN MANGROVE BIOMASS IN WORI VILLAGE, NORTH SULAWESI, INDONESIA

Summary

This ariticle details the findings of a quantitative study on the mangrove ecosystem in Wori Village, North Sulawesi, Indonesia. The research establishes that the 39.56-hectare mangrove area serves as a significant carbon sink, holding an estimated total carbon stock of 12,174 tons. With an average carbon density of 307.74 tons C/ha, the Wori Village ecosystem exceeds the carbon storage capacities of other notable Indonesian mangrove sites, such as Sungaitohor Village and Bontang Mangrove Park.

The study identifies Sonneratia alba as the primary contributor to carbon sequestration in the area due to its substantial trunk diameter, while Avicennia marina provides significant contributions through high population density. These findings underscore the critical role of the Wori mangrove ecosystem in climate change mitigation and highlight the necessity for sustainable conservation management.

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Study Methodology and Scope

The research employed a non-destructive, quantitative descriptive approach to estimate biomass and carbon stocks without felling trees.

• Study Site: Mangrove ecosystem of Wori Village, North Minahasa Regency.
• Survey Conditions: Field surveys were conducted during low tide (0.4 m) on December 6, 2025.
• Sampling Design: A quadrat transect method was utilized, consisting of three 10 m × 10 m plots placed according to land-to-sea zonation.
• Measurement Standards: Diameter at Breast Height (DBH) was measured at 1.3 meters above ground level following SNI (2011) standards.
• Analytical Equations:
  • Aboveground Biomass (AGB): Calculated using the Komiyama et al. (2005) equation: AGB = 0.251 \times \rho \times DBH^{2.46}.
  • Belowground Biomass (BGB): Calculated using the equation: BGB = 0.199 \times \rho^{0.899} \times DBH^{2.22}.
  • Carbon Conversion: Total biomass was converted to carbon stock using a factor of 0.47 (IPCC, 2006).
  • Wood Density: Data sourced from the Global Wood Density Database (Zanne et al., 2009).

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Mangrove Species Composition and Zonation

The study identified four primary mangrove species distributed across three distinct ecological zones. The substrate transitioned from sandy mud near the land to sandy coral debris toward the sea.

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Biomass and Carbon Stock Analysis

The biomass distribution is heavily influenced by both the size (DBH) and the density (number of trees) of the species present.

Aboveground and Belowground Biomass

Sonneratia alba exhibited the highest biomass values across both categories, primarily due to its large average DBH of 47.70 cm. In contrast, Rhizophora apiculata showed the lowest values due to its relatively small average DBH of 11.96 cm.

Table 1: Biomass Distribution by Species

Biomass Ratios

Data indicates a consistent relationship between aboveground and belowground biomass across species. The AGB:BGB ratios range from approximately 2.2 to 3.0:

• Sonneratia alba: Highest ratio (~3.0).
• Bruguiera gymnorrhiza: ~2.8.
• Avicennia marina: ~2.6.
• Rhizophora apiculata: Lowest ratio (~2.2).

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Carbon Stock Estimates

The total carbon stock for the single observation plot (100 m²) was 3,077.43 kg. S. alba and A. marina together account for the vast majority of the sequestered carbon.

Table 2: Carbon Stock Values per Species

Landscape-Scale Conversion

Satellite imagery via ArcMap 10.8 determined the total mangrove forest area in Wori Village to be 39.56 hectares.

Table 3: Total Carbon Stock Conversion Results

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Comparative Analysis and Ecological Significance

The carbon density of Wori Village (307.74 tons C/ha) is exceptionally high when compared to other regional studies. This high value is attributed to the presence of large-diameter trees, specifically S. alba specimens with DBH measurements ranging from 26.46 cm to 58.92 cm.

Comparative Carbon Stocks (tons C/ha):

• Wori Village: 307.74
• Bontang Mangrove Park: 283.04
• Kawal Village: 182.81
• Sungaitohor Village: 131.08

Mangroves are recognized as "blue carbon" ecosystems, capable of sequestering up to four times more carbon than terrestrial forests. The data from Wori Village confirms that these forests are vital reservoirs of organic carbon in their aboveground biomass, belowground biomass, and substrates.

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Conclusion

The mangrove ecosystem in Wori Village represents a high-potential carbon sink that is essential for mitigating global climate change. With a total estimated stock of 12,174 tons of carbon, the area serves as a critical ecological asset for North Sulawesi. The dominance of large-diameter Sonneratia alba and the high density of Avicennia marina are the primary drivers of this storage capacity. To maintain these ecological services, sustainable management and conservation policies are required to protect this significant carbon reservoir.